Hi all! The purpose of the article is to show the nickel plating process from all possible sides. Namely, how to achieve High Quality coatings, will not cost too much on Consumables and perform galvanic work safely. We will also make our own electrolyte from scratch whenever possible, rather than purchasing special chemicals.

If you are already familiar with the copper plating process, note that this process has significant differences. Nickel does not dissolve very well (if at all) in vinegar without special activators.

Nickel plating can be used in many cases, for example:

• Create an anti-corrosion coating that will protect the base metal from oxidation and corrosion. It is often used in Food Industry, to prevent iron contamination of food.
• Increase the hardness of the coated object and thus increase the durability of parts of mechanisms and tools.
• Help with soldering different metals.
• Create all kinds of beautiful decorative finishes.
• A significant thickness of the coating can make the object magnetic.

Note: To achieve different types of coatings (in appearance and properties), you will need to add additional chemicals and metals to achieve the desired result. The reagents will change the way the atoms are positioned relative to themselves and/or add other metals to the coating being applied. If you need an anti-corrosion coating, do not add any chemicals to the electrolyte as they may stain or dull the coating.

Disclaimer - Nickel acetate, the chemical we will be making, is highly toxic. The title of the article suggests that you don't need to play crazy games with strong acids that can leave severe burns on your skin. At the concentrations we will be working with, the process will be “relatively safe.” However, be sure to wash your hands after you finish working and be sure to properly wipe down surfaces (on or near which) chemical residue may have come into contact.

Let's begin.

Step 1: Materials

Almost all consumables can be found at your local supermarket. Finding a source of pure nickel is a little more difficult, but it won't cost more than a couple of dollars. I also highly recommend finding a power supply (AC/DC).

Materials:

• Distilled 5% vinegar;
• Salt;
• Jar with screw cap;
• 6V battery;
• Alligator clips;
• Nitrile gloves;
• Paper towels;
• Acid abrasive Cameo Stainless Steel and Aluminum Cleaner;

Pure nickel - you can “get it” in several different ways.

• Buy two nickel plates on eBay for ~$5;
• You can find nickel-plated welding electrodes at a good hardware store;
• Most music stores sell nickel-plated guitar strings.

You can also remove the nickel coils from old guitar strings if you're strapped for cash. This will take a little time, you will need to use wire cutters and pliers. The largest amount of nickel is contained in strings that consist of a steel core, which can subsequently “contaminate” the electrolyte.

In addition, you can use nickel-plated door handles. I would advise being wary of this option. All because of what exists good chance because they are simply covered with a nickel-like coating.

• High voltage power supply (constant voltage). In the project I used an old 13.5V laptop charger. You can use mobile phone chargers or an old computer power supply.
• Fuse holder;
• A simple wire fuse designed for the borderline operating conditions of the power supply you have chosen.

Step 2: Prepare the power supply

My version of the stand is quite crude, but it is effective. You can (and probably should) make a small box with a jar, a fuse and two terminals that are brought out, to which alligator clips are attached to connect to the power supply.

If you use a mobile phone charger, you will need to do the following:

• Cut off the barrel plug.
• Separate the two wires and shorten one of them by 5-8 cm. This will help prevent accidental short circuits.
• Strip about 6 mm of insulation from the wires.
• Solder a fuse holder to one of them and install the fuse in it.

In the same case, if you use a laptop charger, you will need to do the following:

• Cut off the barrel plug;
• Using a razor blade, remove the outer insulation. Most chargers have one insulated wire that is wrapped in many bare copper wires.
• Twist bare copper wires together to form one core. This will be "earth".
• Solder the fuse holder to it.
• Strip about 6 mm of the insulated wire and tie it to the wires using a plastic fastener or electrical tape, so it does not shorten with the exposed wire.

It is much more difficult to turn a computer power supply into a desktop power supply. The search engine will help you, you will probably find a couple of articles in which everything is described in a similar way.

Note regarding polarities

When carrying out the nickel plating process, it is necessary to determine the polarity of the terminals in advance. Polarity can be determined using a multimeter (voltmeter mode). If you don't have a device on hand, you can mix a pinch of salt with a little water. Take one of the “crocodiles”, connect it to one wire and lower it into the water. Repeat the same procedure with the other wire. A crocodile around which bubbles will appear and will have a negative polarity.

Step 3: Prepare the electrolyte

In principle, you can purchase various nickel salts, but this does not have the spirit of an inventor. I'll show you how you can make nickel acetate much cheaper than buying chemicals. reagents in the store.

Fill the jar with distilled vinegar, leaving about 25 mm from the top. Dissolve a little salt in vinegar. The amount of salt is not so important, but do not overdo it (a pinch should be enough). The reason we add salt is because it increases the conductivity of the vinegar. The greater the amount of current that flows through the vinegar, the faster we can dissolve the nickel. However, too much current will lead to the coating thickness being mercilessly low. Everything needs to be done with economy.

Unlike copper, nickel will not turn into an electrolyte simply by sitting for a while. We need to dissolve nickel with electricity.

Let's place two pieces of pure nickel in vinegar and salt so that parts of both pieces look out of the solution (in the air) and do not touch each other. Let's fix the “crocodile” on one piece of nickel, and then connect it to the positive terminal (we determined the polarity in the previous step). Let's attach the second “crocodile” to another piece of nickel and connect it to the negative terminal of the power supply. Make sure that the clamps do not touch the vinegar, as it will dissolve in it and render the electrolyte unusable.

Hydrogen bubbles will begin to form around the nickel source that is connected to the negative terminal, and oxygen bubbles will begin to form around the positive terminal. To tell the truth, very a small amount of Chlorine gas (from salt) will also form on the positive terminal, but if you do not put a significant amount of salt or use a low voltage, then the concentration of chlorine that dissolves in water will not exceed the permissible limits. Work should be carried out outdoors or in a well-ventilated area.

After some time (in my case about two hours), you will notice that the solution has turned light green. This is nickel acetate. If you get blue, red, yellow or any other colors, the nickel source was not pure. The solution should be clear; if it is cloudy, the nickel source was not pure. The solution and nickel sources may become warm during the process - this is normal. If they feel very hot to the touch, turn off the power, let them cool for an hour, and then turn the power back on (repeat as necessary). You may have added too much salt, which increased the current and power dissipated as heat.

Step 4: Preparing the surface for coating

NOTE. Some metals such as stainless steel, do not allow direct nickel plating. First you will need to create an intermediate copper layer.

The final result will depend on the cleanliness of the surface on which the nickel coating will be applied. Even if the surface looks clean, you still need to clean it (with soap or a cleaner that contains acids).

You can further clean the surface by reverse galvanic decomposition (i.e. "electro-cleaning") within a few seconds. Attach an object to the positive terminal, a "dummy wire" to the negative terminal, and leave them in the vinegar salt solution for 10-30 seconds. This will remove residual oxidation.

Large surfaces can be cleaned with a fine steel brush and vinegar.

Step 5: It's time for galvanizing

In this step, a 6V battery will be used as the power source. Lower voltages (around 1V) will produce a better, shinier, smoother finish. A higher DC voltage power supply can be used for electroplating, but the result will be less than ideal.

Place the nickel source in a nickel acetate solution and connect it to the positive terminal of the battery. Let's attach another clamp to the object that will be nickel-plated and connect it to the negative output of the battery.

Place the object in the solution and wait about 30 seconds. Let's take it out, turn it 180 degrees and place it back into the solution for another 30 seconds. It is necessary to change the location of the clamp to cover the entire surface. Unlike copper plating, the clamp should not leave burn marks.

The solution should bubble around the object.

Step 6:

Nickel does not oxidize when room temperature and does not fade. You can lightly polish the surface to achieve a high shine.

If the nickel plating isn't as shiny as you'd like, polish it with a product that doesn't contain wax or oil and then replate it.

Adding a small amount of tin during the initial plating will change the color (tin gives the color of a white metal such as silver). Many metals can be electrically dissolved in vinegar, like nickel. The two main metals that cannot be electrically dissolved in vinegar are gold and silver (believe me, I've tried). From the last experiment I had some copper electrolyte left over, which I mixed with a nickel solution. The result is a matte, dark gray, very hard surface that looks like a blackboard.

Unless you're an experienced chemist, be very careful when adding random chemicals to a plating bath - you could easily create some kind of toxic gas...

That's all! Thank you for your attention.

Nickel plating, which is a fairly common technological operation, is performed in order to apply a thin layer of nickel to the surface of a metal product. The thickness of such a layer, the size of which can be adjusted using various techniques, can vary from 0.8 to 55 microns.

Nickel plating is used as a protective and decorative coating, as well as to obtain an underlayer when chrome plating

Using nickel plating of metal, it is possible to form a film that provides reliable protection from such negative phenomena as oxidation, the development of corrosion processes, reactions caused by interaction with salt, alkaline and acidic environments. In particular, nickel-plated pipes, which are actively used for the production of sanitary products, have become very widespread.

The most common types of nickel plating are:

• metal products that will be used on outdoors;
• body parts of motorcycles and motor vehicles, including those for the manufacture of which aluminum alloy was used;
• equipment and instruments used in general medicine and dentistry;
• metal products that are used in water for a long time;
• enclosing structures made of steel or aluminum alloys;
• metal products exposed to strong chemical substances.

There are several methods of nickel plating of metal products used both in production and at home. Of greatest practical interest are methods of nickel plating of metal parts that do not require the use of complex technological equipment and sold at home. These methods include electrolytic and chemical nickel plating.

Electrolytic nickel plating

The essence of the technology of electrolytic nickel plating of metal parts, which also has another name – “galvanic nickel plating”, can be considered using the example of how copper plating of the surface of a metal product is carried out. This procedure can be carried out both with and without the use of an electrolytic solution.

The part that will be further processed in an electrolytic solution is subjected to careful processing, for which the oxide film is removed from its surface using sandpaper. Then the product to be treated is washed in warm water and treated with a soda solution, after which it is washed again with water.

The nickel plating process itself is carried out in a glass container into which an aqueous solution (electrolyte) is poured. This solution contains 20% copper sulfate and 2% sulfuric acid. The workpiece, on the surface of which it is necessary to apply a thin layer of copper, is placed in an electrolyte solution between two copper anodes. To start the copper plating process, an electric current must be applied to the copper anodes and the workpiece, the value of which is calculated based on the indicator 10–15 mA per square centimeter of the part area. A thin layer of copper on the surface of the product appears after half an hour of its presence in the electrolyte solution, and such a layer will become thicker the longer the process takes place.

You can apply a copper layer to the surface of the product using another technology. To do this, you need to make a copper brush (you can use a stranded wire, having first removed the insulating layer from it). Such a hand-made brush must be fixed on a wooden stick, which will serve as a handle.

The product, the surface of which has been previously cleaned and degreased, is placed in a container made of dielectric material and filled with an electrolyte, which can be a saturated aqueous solution of copper sulfate. A homemade brush is connected to the positive contact of the source electric current, and the workpiece – to its minus. After this, the copper plating procedure begins. It consists in passing a brush, which is previously dipped in electrolyte, over the surface of the product without touching it. Using this technique, the coating can be applied in several layers, which will allow the formation of a copper layer on the surface of the product, on which there are practically no pores.

Electrolytic nickel plating is performed using a similar technology: it also uses an electrolyte solution. Just as in the case of copper plating, the workpiece is placed between two anodes, only in in this case they are made of nickel. The anodes placed in the nickel plating solution are connected to the positive contact of the current source, and the product suspended between them on a metal wire is connected to the negative one.

To carry out nickel plating, including do-it-yourself, electrolytic solutions of two main types are used:

• aqueous solution containing nickel sulfate, sodium and magnesium (14:5:3), 2% boric acid, 0,5% table salt;
• solution based neutral water, containing 30% nickel sulfate, 4% nickel chloride, 3% boric acid.

Bright nickel plating electrolyte with the addition of organic brightening agents (sodium salts)

Bright nickel plated equalizing electrolyte. Suitable for surfaces with low cleaning class

To prepare an electrolytic solution, add one liter of neutral water to the dry mixture of the above elements and mix thoroughly. If a precipitate has formed in the resulting solution, get rid of it. Only after this the solution can be used to perform nickel plating.

Treatment with this technology usually lasts half an hour, using a current source with a voltage of 5.8–6 V. The result is a surface covered with an uneven matte gray color. To make it beautiful and shiny, you need to clean it and polish it. It should be borne in mind that this technology cannot be used for parts with high surface roughness or narrow and deep holes. In such cases, coating the surface of a metal product with a layer of nickel should be done using chemical technology, which is also called blackening.

The essence of the technological operation of blackening is that an intermediate coating is first applied to the surface of the product, the base of which can be zinc or nickel, and on the top of such a coating a layer of black nickel no more than 2 microns thick is formed. Nickel plating, made using blackening technology, looks very beautiful and provides reliable protection of the metal from negative influences various factors external environment.

In some cases, a metal product is simultaneously subjected to two technological operations, such as nickel plating and chrome plating.

Electroless nickel plating

The procedure for chemical nickel plating of metal products is carried out according to the following scheme: the workpiece is immersed in a boiling solution for some time, as a result of which nickel particles settle on its surface. When using this technology, there is no electrochemical effect on the metal from which the part is made.

The result of using this nickel plating technology is the formation of a nickel layer on the surface of the workpiece, which is firmly bonded to the base metal. This method of nickel plating can achieve the greatest efficiency in cases where it is used to process objects made of steel alloys.

It is not difficult to carry out such nickel plating at home or even in a garage. In this case, the nickel plating procedure takes place in several stages.

• The dry reagents from which the electrolytic solution will be prepared are mixed with water in enamel dishes.
• The resulting solution is brought to a boil, and then sodium hypophosphite is added to it.
• The product that needs to be processed is placed in an electrolytic solution, and this is done so that it does not touch the side walls and bottom of the container. In fact, it is necessary to make household appliance for nickel plating, the design of which will consist of an enameled container of the appropriate volume, as well as a dielectric bracket on which the workpiece will be fixed.
• The duration of boiling of the electrolytic solution, depending on its chemical composition, can range from one hour to three.
• After completion of the technological operation, the nickel-plated part is removed from the solution. It is then washed in water containing slaked lime. After thorough washing, the surface of the product is polished.

Electrolytic solutions for nickel plating, which can be applied not only to steel, but also to brass, aluminum and other metals, must contain chemical composition the following elements - nickel chloride or sulfate, sodium hypophosphite of varying acidity, any of the acids.

To increase the speed of nickel plating of metal products, lead is added to the composition for performing this technological operation. As a rule, in one liter of electrolytic solution, nickel coating is performed on a surface whose area is 20 cm 2. In electrolytic solutions with higher acidity, nickel plating of ferrous metal products is carried out, and in alkaline solutions, brass is processed, aluminum or stainless steel parts are nickel-plated.

Some nuances of technology

Carrying out nickel plating of brass and steel products various brands and other metals, some nuances of this technological operation should be taken into account.

• The nickel film will be more stable if it is applied to a previously copper-plated surface. The nickel-plated surface will be even more stable if the finished product is subjected to heat treatment, which consists of holding it at a temperature exceeding 450°.
• If parts made of hardened steel are subjected to nickel plating, then they can be heated and held at a temperature not exceeding 250–300°, otherwise they may lose their hardness.
• When nickel plating products that differ large sizes, there is a need for constant stirring and regular filtration of the electrolytic solution. This complexity is especially typical for nickel plating processes performed not in industrial conditions, but at home.

Using a technology similar to nickel plating, it is possible to coat brass, steel and other metals with a layer of silver. A coating of this metal is applied, in particular, to fishing gear and other products to prevent them from tarnishing.

The procedure for applying a layer of silver to steel, brass and other metals differs from traditional nickel plating not only in the application temperature and holding time, but also in the fact that an electrolytic solution of a certain composition is used for it. In this case, this operation is performed in a solution whose temperature is 90°.

Nickel plating of metal products allows not only to protect their surfaces from corrosion, but also to create a shiny coating on them. Such products are widely used in the manufacture of plumbing fixtures, automobile parts, medical instruments, etc. In this regard, many people wonder whether it is possible to nickel plating steel at home?

Metal nickel plating technology

Nickel plating is carried out by applying a thin layer of nickel coating to a metal object. Nickel coating can be used on products made from various metals, such as:

• steel;
• copper;
• titanium;
• aluminum.

There are metals that cannot be nickel-plated:

• tin;
• lead;
• cadmium;
• antimony.

Nickel coating protects the product from moisture and various aggressive substances. It is often applied as a base layer before chrome plating parts. After applying a thin film of nickel, platings of silver, gold and other metals are held more firmly.

At home, methods are used that do not require the use of specialized equipment. Thanks to this, nickel plating of steel, copper, and aluminum at home is accessible to almost every person. To obtain a uniform coating, you must first prepare the part.

How to prepare a product for nickel plating?

Preparing the product is a rather labor-intensive process. The presence of corrosion, oxidation, etc. should be completely eliminated. Preparation is carried out in several stages.

Sandblasting

This type of processing can be performed as a specialized sandblaster, and homemade. During processing, you should try to remove as much foreign deposits as possible from the surface of the workpiece. Particular attention should be paid to hard-to-reach places. They should be cleaned in the same way as other surface areas.

Grinding

In order for the nickel coating to be uniform, you need to level the surface as much as possible. Grinding makes it possible to clean an object from an oxide film. To complete this step, use sandpaper, as well as various tools and devices designed for grinding.

Advice: Do not neglect polishing the workpieces, improper preparation may lead to peeling of the coating.

Removing grease stains

After the grinding process is completed, the resulting contaminants should be washed off under running water. Then you will need to degrease the workpiece. To do this, you can use both ready-made and homemade solvents. After applying the solvent, the part must be rinsed again with water and dried thoroughly.

Attention: When choosing a solvent, it is necessary to take into account the degree of its impact on the metal from which the product is made. It is prohibited to use degreasing solutions that enter into chemical reaction with the surface.

Copper plating

Nickel plating of a product is best done with preliminary copper plating of the workpiece. This step is optional, but nickel plating on steel and other metals will be of better quality if the plating is applied to a thin layer of copper.

To copper plating a part, it is necessary to place it in a glass container with an aqueous electrolyte consisting of copper sulfate and sulfuric acid. The object is suspended on the wire so that it does not touch the walls and bottom of the container. Copper plates, which are electrodes, are placed on both sides of the workpiece. After this, a source is connected to the electrodes and the workpiece direct current. The degree of copper plating directly depends on the time of the process.

Nickel plating methods

Nickel plating of a product at home can be done in two ways: chemical and electrolytic.

Electrolytic method

Plating using an electrolyte is called electroplating. First you need to prepare an aqueous solution (electrolyte). The following components are required for this:

• nickel sulfate– 70 g;
• magnesium sulfate– 15 g;
• salt– 2.5 g;
• sodium sulfate– 25 g;
• boric acid– 10g;
• water– 500g.

Each component must be separately dissolved in water and filtered. The resulting solutions are mixed and poured into a glass container. For galvanic nickel plating, nickel electrodes are placed in a vessel with an electrolyte. To ensure uniform coating on the workpiece, at least two electrodes are installed on all sides.

The prepared workpiece is placed in a vessel between the electrodes so that it does not touch the walls and bottom of the container. The electrodes are connected to each other by copper conductors and connected to the positive contact of a direct current source. The current-carrying wire is connected to the negative terminal.

During the process of nickel plating steel, the supply voltage should not exceed 6 Volts. The current density should be controlled; it should not exceed 1.2 A. The process takes about 30–40 minutes. Upon completion, the item must be rinsed with running water and dried thoroughly. The applied coating should be matte and smooth. In order for the surface of the product to acquire shine, it will need to be polished.

Chemical method

Nickel plating of steel and other metals chemically differs from galvanic coating in the durability of the coating. Using chemical nickel plating, you can easily apply the substance to even the most inaccessible places.

Water is poured into an enamel bowl and sodium succinic acid and nickel chloride are dissolved in it. Then the solution is heated to a temperature of 90 degrees. Once the required temperature is reached, sodium hypophosphite is added. The product is carefully suspended above the container with the solution. The amount of liquid is calculated based on the fact that 1 liter of solution can cover a surface area of ​​2 dm2.

Nickel plating is controlled visually: when the part is evenly covered with a film, the process is completed. When finished, the part must be washed in a solution made from water and a small amount of chalk. After this, the part is dried and polished.

How to increase the service life of the coating?

The resulting coating has a porous structure. Therefore, the metal of the product is susceptible to corrosion. To reduce the risk of its occurrence, the nickel layer is coated with lubricants. After applying them, the item is immersed in a container with fish oil. After 24 hours, its excess is removed using a solvent.

If the product is large in size and it is impossible to immerse it in a container, then its surface is simply rubbed with fish oil. This procedure will need to be carried out twice, with a time interval of about 12 hours. 48 hours after treatment, remaining fat must be removed.

There are two ways to carry out nickel plating of steel at home. This process is simple, but requires careful preparation and extreme care when performing. It is necessary to purchase high-quality components for preparing the solution, prepare in advance work area, containers, tools and devices.

During work, it is important to observe safety precautions: protect your eyes and skin from the ingress of chemicals, ensure sufficient ventilation of the room, prevent the possibility of ignition of the mixture and the electrical installation.

Information for action
(technology tips)
Erlykin L.A. "Do It Yourself" 3-92

None of the home craftsmen has ever faced the need to nickel-plate or chrome-plate this or that part. What do-it-yourselfer hasn’t dreamed of installing a “non-working” bushing with a hard, wear-resistant surface obtained by saturating it with boron in a critical component. But how to do at home what is usually done at specialized enterprises using chemical-thermal and electrochemical processing of metals. You won’t build gas and vacuum furnaces at home, or construct electrolysis baths. But it turns out that there is no need to build all this at all. It is enough to have some reagents on hand, an enamel pan and, perhaps, blowtorch, and also know the recipes of “chemical technology”, with the help of which metals can also be copper-plated, cadmium-plated, tin-plated, oxidized, etc.

So, let's begin to get acquainted with the secrets of chemical technology. Please note that the content of components in the solutions given is usually given in g/l. If other units are used, a special disclaimer follows.

Preparatory operations

Before applying paints, protective and decorative films, and also before covering them with other metals, it is necessary to carry out preparatory operations, that is, remove contamination from these surfaces of different nature. Please note that the final result of all work greatly depends on the quality of the preparatory operations.

Preparatory operations include degreasing, cleaning and pickling.

Degreasing

The process of degreasing the surface of metal parts is carried out, as a rule, when these parts have just been processed (ground or polished) and there is no rust, scale or other foreign products on their surface.

Using degreasing, oil and grease films are removed from the surface of parts. For this purpose, aqueous solutions of certain chemical reagents are used, although organic solvents can also be used for this. The latter have the advantage that they do not have a subsequent corrosive effect on the surface of the parts, but at the same time they are toxic and flammable.

Aqueous solutions. Degreasing of metal parts in aqueous solutions is carried out in enamel containers. Pour in water, dissolve chemicals in it and place on low heat. Upon reaching desired temperature parts are loaded into the solution. During processing, the solution is stirred. Below are the compositions of degreasing solutions (g/l), as well as the operating temperatures of the solutions and the processing time of the parts.

Compositions of degreasing solutions (g/l)

For ferrous metals (iron and iron alloys)

Liquid glass (stationery silicate glue) - 3...10, caustic soda (potassium) - 20...30, trisodium phosphate - 25...30. Solution temperature - 70...90° C, processing time - 10...30 minutes.

Liquid glass - 5...10, caustic soda - 100...150, soda ash - 30...60. Solution temperature - 70...80°C, processing time - 5...10 minutes.

Liquid glass - 35, trisodium phosphate - 3...10. Solution temperature - 70...90°C, processing time - 10...20 minutes.

Liquid glass - 35, trisodium phosphate - 15, drug - emulsifier OP-7 (or OP-10) -2. Solution temperature - 60-70°C, processing time - 5...10 minutes.

Liquid glass - 15, preparation OP-7 (or OP-10) -1. Solution temperature - 70...80°C, processing time - 10...15 minutes.

Soda ash - 20, potassium chromium - 1. Solution temperature - 80...90°C, processing time - 10...20 minutes.

Soda ash - 5...10, trisodium phosphate - 5...10, preparation OP-7 (or OP-10) - 3. Solution temperature - 60...80 ° C, treatment time - 5...10 min .

For copper and copper alloys

Caustic soda - 35, soda ash - 60, trisodium phosphate - 15, preparation OP-7 (or OP-10) - 5. Solution temperature - 60...70, processing time - 10...20 minutes.

Caustic soda (potassium) - 75, liquid glass - 20 Solution temperature - 80...90°C, processing time - 40...60 minutes.

Liquid glass - 10...20, trisodium phosphate - 100. Solution temperature - 65...80 C, processing time - 10...60 minutes.

Liquid glass - 5...10, soda ash - 20...25, preparation OP-7 (or OP-10) - 5...10. Solution temperature - 60...70°C, processing time - 5...10 minutes.

Trisodium phosphate - 80...100. Solution temperature - 80...90°C, processing time - 30...40 minutes.

For aluminum and its alloys

Liquid glass - 25...50, soda ash - 5...10, trisodium phosphate - 5...10, preparation OP-7 (or OP-10) - 15...20 min.

Liquid glass - 20...30, soda ash - 50...60, trisodium phosphate - 50...60. Solution temperature - 50...60°C, processing time - 3...5 minutes.

Soda ash - 20...25, trisodium phosphate - 20...25, preparation OP-7 (or OP-10) - 5...7. Temperature - 70...80°C, processing time - 10...20 minutes.

For silver, nickel and their alloys

Liquid glass - 50, soda ash - 20, trisodium phosphate - 20, preparation OP-7 (or OP-10) - 2. Solution temperature - 70...80°C, processing time - 5...10 minutes.

Liquid glass - 25, soda ash - 5, trisodium phosphate - 10. Solution temperature - 75...85°C, processing time - 15...20 minutes.

For zinc

Liquid glass - 20...25, caustic soda - 20...25, soda ash - 20...25. Solution temperature - 65...75°C, processing time - 5 minutes.

Liquid glass - 30...50, soda ash - 30....50, kerosene - 30...50, preparation OP-7 (or OP-10) - 2...3. Solution temperature - 60-70°C, processing time - 1...2 minutes.

Organic solvents

The most commonly used organic solvents are B-70 gasoline (or “gasoline for lighters”) and acetone. However, they have a significant drawback - they are easily flammable. Therefore, recently they have been replaced by non-flammable solvents such as trichlorethylene and perchlorethylene. Their dissolving ability is much higher than that of gasoline and acetone. Moreover, these solvents can be safely heated, which greatly speeds up the degreasing of metal parts.

Degreasing the surface of metal parts using organic solvents is carried out in the following sequence. The parts are loaded into a container with solvent and kept for 15...20 minutes. Then the surface of the parts is wiped directly in the solvent with a brush. After this treatment, the surface of each part is carefully treated with a swab moistened with 25% ammonia (you must work with rubber gloves!).

All degreasing work with organic solvents is carried out in a well-ventilated area.

Cleaning

In this section, the process of cleaning engine carbon deposits will be considered as an example. internal combustion. As is known, carbon deposits are asphalt-resinous substances that form difficult-to-remove films on the working surfaces of engines. Removing carbon deposits is a rather difficult task, since the carbon film is inert and firmly adhered to the surface of the part.

Compositions of cleaning solutions (g/l)

For ferrous metals

Liquid glass - 1.5, soda ash - 33, caustic soda - 25, laundry soap - 8.5. Solution temperature - 80...90°C, processing time - 3 hours.

Caustic soda - 100, potassium dichromate - 5. Solution temperature - 80...95 ° C, processing time - up to 3 hours.

Caustic soda - 25, liquid glass - 10, sodium bichromate - 5, laundry soap- 8, soda ash - 30. Solution temperature - 80...95 ° C, processing time - up to 3 hours.

Caustic soda - 25, liquid glass - 10, laundry soap - 10, potash - 30. Solution temperature - 100°C, processing time - up to 6 hours.

For aluminum (duralumin) alloys

Liquid glass 8.5, laundry soap - 10, soda ash - 18.5. Solution temperature - 85...95 C, processing time - up to 3 hours.

Liquid glass - 8, potassium bichromate - 5, laundry soap - 10, soda ash - 20. Solution temperature - 85...95 ° C, processing time - up to 3 hours.

Soda ash - 10, potassium bichromate - 5, laundry soap - 10. Solution temperature - 80...95 ° C, processing time - up to 3 hours.

Etching

Pickling (as a preparatory operation) allows you to remove contaminants (rust, scale and other corrosion products) from metal parts that are firmly adhered to their surface.

The main purpose of etching is to remove corrosion products; in this case, the base metal should not be etched. To prevent metal etching, special additives are added to the solutions. Good results gives the use of small quantities of hexamethylenetetramine (urotropine). To all solutions for etching ferrous metals, add 1 tablet (0.5 g) of hexamine per 1 liter of solution. In the absence of urotropine, it is replaced with the same amount of dry alcohol (sold in sporting goods stores as fuel for tourists).

Due to the fact that inorganic acids are used in etching recipes, it is necessary to know their initial density (g/cm3): Nitric acid - 1,4, sulfuric acid- 1.84; hydrochloric acid - 1.19; orthophosphoric acid - 1,7; acetic acid - 1,05.

Compositions of etching solutions

For ferrous metals

Sulfuric acid - 90...130, hydrochloric acid - 80...100. Solution temperature - 30...40°C, processing time - 0.5...1.0 hours.

Sulfuric acid - 150...200. Solution temperature - 25...60°C, processing time - 0.5...1.0 hours.

Hydrochloric acid - 200. Solution temperature - 30...35°C, processing time - 15...20 minutes.

Hydrochloric acid - 150...200, formalin - 40...50. Solution temperature 30...50°C, processing time 15...25 minutes.

Nitric acid - 70...80, hydrochloric acid - 500...550. Solution temperature - 50°C, processing time - 3...5 minutes.

Nitric acid - 100, sulfuric acid - 50, hydrochloric acid - 150. Solution temperature - 85°C, treatment time - 3...10 minutes.

Hydrochloric acid - 150, orthophosphoric acid - 100. Solution temperature - 50°C, processing time - 10...20 minutes.

The last solution (when processing steel parts), in addition to cleaning the surface, also phosphates it. And phosphate films on the surface of steel parts allow them to be painted with any paint without primer, since these films themselves serve as an excellent primer.

Here are a few more recipes for etching solutions, the compositions of which this time are given in % (by weight).

Orthophosphoric acid - 10, butyl alcohol - 83, water - 7. Solution temperature - 50...70°C, processing time - 20...30 minutes.

Orthophosphoric acid - 35, butyl alcohol - 5, water - 60. Solution temperature - 40...60°C, processing time - 30...35 minutes.

After etching ferrous metals, they are washed in a 15% solution of soda ash (or drinking soda). Then rinse thoroughly with water.

Note that below the compositions of the solutions are again given in g/l.

For copper and its alloys

Sulfuric acid - 25...40, chromic anhydride - 150...200. Solution temperature - 25°C, processing time - 5...10 minutes.

Sulfuric acid - 150, potassium dichromate - 50. Solution temperature - 25.35 ° C, processing time - 5...15 minutes.

Trilon B-100. Solution temperature - 18...25°C, processing time - 5...10 minutes.

Chromic anhydride - 350, sodium chloride - 50. Solution temperature - 18...25°C, processing time - 5...15 minutes.

For aluminum and its alloys

Caustic soda -50...100. Solution temperature - 40...60°C, processing time - 5...10 s.

Nitric acid - 35...40. Solution temperature - 18...25°C, processing time - 3...5 s.

Caustic soda - 25...35, soda ash - 20...30. Solution temperature - 40...60°C, processing time - 0.5...2.0 minutes.

Caustic soda - 150, sodium chloride - 30. Solution temperature - 60°C, processing time - 15...20 s.

Chemical polishing

Chemical polishing allows you to quickly and efficiently process the surfaces of metal parts. The great advantage of this technology is that with the help of it (and only it!) it is possible to polish parts with a complex profile at home.

Compositions of solutions for chemical polishing

For carbon steels (the content of components is indicated in each specific case in certain units (g/l, percentage, parts)

Nitric acid - 2.-.4, hydrochloric acid 2...5, Phosphoric acid - 15...25, the rest is water. Solution temperature - 70...80°C, processing time - 1...10 minutes. Contents of components - in% (by volume).

Sulfuric acid - 0.1, acetic acid - 25, hydrogen peroxide (30%) - 13. Solution temperature - 18...25°C, treatment time - 30...60 minutes. Content of components - in g/l.

Nitric acid - 100...200, sulfuric acid - 200...600, hydrochloric acid - 25, Orthophosphoric acid - 400. Mixture temperature - 80...120°C, processing time - 10...60 s. Content of components in parts (by volume).

For stainless steel

Sulfuric acid - 230, hydrochloric acid - 660, acid orange dye - 25. Solution temperature - 70...75°C, processing time - 2...3 minutes. Content of components - in g/l.

Nitric acid - 4...5, hydrochloric acid - 3...4, Phosphoric acid - 20..30, methyl orange - 1..1.5, the rest is water. Solution temperature - 18...25°C, processing time - 5...10 minutes. Contents of components - in% (by weight).

Nitric acid - 30...90, potassium ferric sulfide (yellow blood salt) - 2...15 g/l, preparation OP-7 - 3...25, hydrochloric acid - 45..110, orthophosphoric acid - 45. ..280.

Solution temperature - 30...40°C, processing time - 15...30 minutes. Content of components (except for yellow blood salt) - in pl/l.

The latter composition is suitable for polishing cast iron and any steels.

For copper

Nitric acid - 900, sodium chloride - 5, soot - 5. Solution temperature - 18...25°C, treatment time - 15...20 s. Component content - g/l.

Attention! Sodium chloride is introduced into solutions last, and the solution must be pre-cooled!

Nitric acid - 20, sulfuric acid - 80, hydrochloric acid - 1, chromic anhydride - 50. Solution temperature - 13..18°C, treatment time - 1...2 min. Component content - in ml.

Nitric acid 500, sulfuric acid - 250, sodium chloride - 10. Solution temperature - 18...25°C, treatment time - 10...20 s. Content of components - in g/l.

For brass

Nitric acid - 20, hydrochloric acid - 0.01, acetic acid - 40, orthophosphoric acid - 40. Mixture temperature - 25...30 ° C, processing time - 20...60 s. Component content - in ml.

Copper sulfate ( copper sulfate) - 8, sodium chloride - 16, acetic acid - 3, water - the rest. Solution temperature - 20°C, processing time - 20...60 minutes. Component content - in% (by weight).

For bronze

Phosphoric acid - 77...79, potassium nitrate - 21...23. Mixture temperature - 18°C, processing time - 0.5-3 minutes. Component content - in% (by weight).

Nitric acid - 65, sodium chloride - 1 g, acetic acid - 5, orthophosphoric acid - 30, water - 5. Solution temperature - 18...25 ° C, treatment time - 1...5 s. Contents of components (except sodium chloride) - in ml.

For nickel and its alloys (nickel silver and nickel silver)

Nitric acid - 20, acetic acid - 40, orthophosphoric acid - 40. Mixture temperature - 20°C, processing time - up to 2 minutes. Component content - in% (by weight).

Nitric acid - 30, acetic acid (glacial) - 70. Mixture temperature - 70...80°C, processing time - 2...3 s. Content of components - in% (by volume).

For aluminum and its alloys

Orthophosphoric acid - 75, sulfuric acid - 25. Mixture temperature - 100°C, processing time - 5...10 minutes. Contents of components - in parts (by volume).

Phosphoric acid - 60, sulfuric acid - 200, nitric acid - 150, urea - 5g. Mixture temperature - 100°C, processing time - 20 s. Content of components (except urea) - in ml.

Orthophosphoric acid - 70, sulfuric acid - 22, boric acid - 8. Mixture temperature - 95°C, processing time - 5...7 minutes. Contents of components - in parts (by volume).

Passivation

Passivation is the process of chemically creating an inert layer on the surface of a metal that prevents the metal itself from oxidizing. The process of passivation of the surface of metal products is used by minters when creating their works; craftsmen - in production various crafts(chandeliers, sconces and other household items); sports fishermen passivate their homemade metal baits.

Compositions of solutions for passivation (g/l)

For ferrous metals

Sodium nitrite - 40...100. Solution temperature - 30...40°C, processing time - 15...20 minutes.

Sodium nitrite - 10...15, soda ash - 3...7. Solution temperature - 70...80°C, processing time - 2...3 minutes.

Sodium nitrite - 2...3, soda ash - 10, preparation OP-7 - 1...2. Solution temperature - 40...60°C, processing time - 10...15 minutes.

Chromic anhydride - 50. Solution temperature - 65...75 "C, processing time - 10...20 minutes.

For copper and its alloys

Sulfuric acid - 15, potassium bichromate - 100. Solution temperature - 45°C, processing time - 5...10 minutes.

Potassium dichromate - 150. Solution temperature - 60°C, processing time - 2...5 minutes.

For aluminum and its alloys

Orthophosphoric acid - 300, chromic anhydride - 15. Solution temperature - 18...25°C, processing time - 2...5 minutes.

Potassium dichromate - 200. Solution temperature - 20°C, “processing time -5...10 min.

For silver

Potassium dichromate - 50. Solution temperature - 25...40°C, processing time - 20 minutes.

For zinc

Sulfuric acid - 2...3, chromic anhydride - 150...200. Solution temperature - 20°C, processing time - 5...10 s.

Phosphating

As already mentioned, the phosphate film on the surface of steel parts is a fairly reliable anti-corrosion coating. It is also an excellent primer for paintwork.

Some low-temperature phosphating methods are applicable for car body treatments passenger cars before coating them with anti-corrosion and anti-wear compounds.

Compositions of solutions for phosphating (g/l)

For steel

Majef (manganese and iron phosphate salts) - 30, zinc nitrate - 40, sodium fluoride - 10. Solution temperature - 20°C, treatment time - 40 minutes.

Monozinc phosphate - 75, zinc nitrate - 400...600. Solution temperature - 20°C, processing time - 20...30 s.

Majef - 25, zinc nitrate - 35, sodium nitrite - 3. Solution temperature - 20°C, treatment time - 40 minutes.

Monoammonium phosphate - 300. Solution temperature - 60...80°C, processing time - 20...30 s.

Orthophosphoric acid - 60...80, chromic anhydride - 100...150. Solution temperature - 50...60°C, processing time - 20...30 minutes.

Orthophosphoric acid - 400...550, butyl alcohol - 30. Solution temperature - 50°C, processing time - 20 minutes.

Application metal coatings

Chemical coating of some metals with others is captivating with its simplicity technological process. Indeed, if, for example, it is necessary to chemically nickel-plate any steel part, it is enough to have suitable enameled utensils and a heating source ( gas stove, Primus, etc.) and relatively scarce chemicals. An hour or two - and the part is covered with a shiny layer of nickel.

Note that only with the help of chemical nickel plating can parts be reliably nickel-plated complex profile, internal cavities (pipes, etc.). True, chemical nickel plating (and some other similar processes) is not without its drawbacks. The main one is that the adhesion of the nickel film to the base metal is not too strong. However, this drawback can be eliminated; for this, the so-called low-temperature diffusion method is used. It allows you to significantly increase the adhesion of the nickel film to the base metal. This method is applicable to all chemical coatings of some metals with others.

Nickel plating

The chemical nickel plating process is based on the reduction of nickel from aqueous solutions of its salts using sodium hypophosphite and some other chemicals.

Chemically produced nickel coatings have an amorphous structure. The presence of phosphorus in nickel makes the film similar in hardness to a chromium film. Unfortunately, the adhesion of the nickel film to the base metal is relatively low. Thermal treatment of nickel films (low-temperature diffusion) consists of heating nickel-plated parts to a temperature of 400°C and holding them at this temperature for 1 hour.

If the parts coated with nickel are hardened (springs, knives, fishhooks, etc.), then at a temperature of 40°C they can be tempered, that is, they can lose their main quality - hardness. In this case, low-temperature diffusion is carried out at a temperature of 270...300 C with a holding time of up to 3 hours. In this case, heat treatment also increases the hardness of the nickel coating.

All of the listed advantages of chemical nickel plating have not escaped the attention of technologists. They found them practical use(except for the use of decorative and anti-corrosion properties). Thus, with the help of chemical nickel plating, axes of various mechanisms, worms of thread-cutting machines, etc. are repaired.

At home, using nickel plating (chemical, of course!) you can repair parts of various household devices. The technology here is extremely simple. For example, the axis of some device was demolished. Then a layer of nickel is built up (in excess) on the damaged area. Then the working area of ​​the axle is polished, bringing it to the desired size.

It should be noted that chemical nickel plating cannot be used to coat metals such as tin, lead, cadmium, zinc, bismuth and antimony.
Solutions used for chemical nickel plating are divided into acidic (pH - 4...6.5) and alkaline (pH - above 6.5). Acidic solutions are preferably used for coating ferrous metals, copper and brass. Alkaline - for stainless steels.

Acidic solutions (compared to alkaline ones) on a polished part give a smoother (mirror-like) surface, they have less porosity, and the process speed is higher. Another important feature of acidic solutions: they are less likely to self-discharge when the operating temperature is exceeded. (Self-discharge is the instantaneous precipitation of nickel into the solution with the latter splashing.)

Alkaline solutions have the main advantage of more reliable adhesion of the nickel film to the base metal.

And one last thing. Water for nickel plating (and when applying other coatings) is taken distilled (you can use condensate from household refrigerators). Chemical reagents are suitable at least clean (designation on the label - C).

Before covering parts with any metal film, it is necessary to carry out special preparation of their surface.

The preparation of all metals and alloys is as follows. The treated part is degreased in one of the aqueous solutions, and then the part is pickled in one of the solutions listed below.

Compositions of solutions for pickling (g/l)

For steel

Sulfuric acid - 30...50. Solution temperature - 20°C, processing time - 20...60 s.

Hydrochloric acid - 20...45. Solution temperature - 20°C, processing time - 15...40 s.

Sulfuric acid - 50...80, hydrochloric acid - 20...30. Solution temperature - 20°C, processing time - 8...10 s.

For copper and its alloys

Sulfuric acid - 5% solution. Temperature - 20°C, processing time - 20s.

For aluminum and its alloys

Nitric acid. (Attention, 10...15% solution.) Solution temperature - 20°C, processing time - 5...15 s.

Please note that for aluminum and its alloys, before chemical nickel plating, another treatment is carried out - the so-called zincate treatment. Below are solutions for zincate treatment.

For aluminum

Caustic soda - 250, zinc oxide - 55. Solution temperature - 20 C, processing time - 3...5 s.

Caustic soda - 120, zinc sulfate - 40. Solution temperature - 20°C, processing time - 1.5...2 minutes.

When preparing both solutions, first dissolve caustic soda separately in half of the water, and the zinc component in the other half. Then both solutions are poured together.

For cast aluminum alloys

Caustic soda - 10, zinc oxide - 5, Rochelle salt (crystalline hydrate) - 10. Solution temperature - 20 C, processing time - 2 minutes.

For wrought aluminum alloys

Ferric chloride (crystalline hydrate) - 1, caustic soda - 525, zinc oxide 100, Rochelle salt - 10. Solution temperature - 25 ° C, processing time - 30...60 s.

After zincate treatment, the parts are washed in water and hung in a nickel plating solution.

All solutions for nickel plating are universal, that is, suitable for all metals (although there are some specifics). They are prepared in a certain sequence. So, all chemical reagents (except for sodium hypophosphite) are dissolved in water (enamel dishes!). Then the solution is heated to operating temperature and only after that sodium hypophosphite is dissolved and the parts are hung in the solution.

In 1 liter of solution you can nickel-plate a surface with an area of ​​up to 2 dm2.

Compositions of solutions for nickel plating (g/l)

Nickel sulfate - 25, sodium succinate - 15, sodium hypophosphite - 30. Solution temperature - 90°C, pH - 4.5, film growth rate - 15...20 µm/h.

Nickel chloride - 25, sodium succinate - 15, sodium hypophosphite - 30. Solution temperature - 90...92°C, pH - 5.5, growth rate - 18...25 µm/h.

Nickel chloride - 30, glycolic acid - 39, sodium hypophosphite - 10. Solution temperature 85,..89 ° C, pH - 4.2, growth rate - 15...20 µm/h.

Nickel chloride - 21, sodium acetate - 10, sodium hypophosphite - 24, solution temperature - 97°C, pH - 5.2, growth rate - up to 60 µm/h.

Nickel sulfate - 21, sodium acetate - 10, lead sulfide - 20, sodium hypophosphite - 24. Solution temperature - 90°C, pH - 5, growth rate - up to 90 µm/h.

Nickel chloride - 30, acetic acid - 15, lead sulfide - 10...15, sodium hypophosphite - 15. Solution temperature - 85...87 ° C, pH - 4.5, growth rate - 12...15 µm /h.

Nickel chloride - 45, ammonium chloride - 45, sodium citrate - 45, sodium hypophosphite - 20. Solution temperature - 90°C, pH - 8.5, growth rate - 18... 20 µm/h.

Nickel chloride - 30, ammonium chloride - 30, sodium succinate - 100, ammonia (25% solution - 35, sodium hypophosphite - 25).
Temperature - 90°C, pH - 8...8.5, growth rate - 8...12 µm/h.

Nickel chloride - 45, ammonium chloride - 45, sodium acetate - 45, sodium hypophosphite - 20. Solution temperature - 88...90°C, pH - 8...9, growth rate - 18...20 µm/ h.

Nickel sulfate - 30, ammonium sulfate - 30, sodium hypophosphite - 10. Solution temperature - 85°C, pH - 8.2...8.5, growth rate - 15...18 µm/h.

Attention! According to existing GOSTs, a single-layer nickel coating per 1 cm2 has several dozen through pores (to the base metal). Naturally, in the open air, a steel part coated with nickel will quickly become covered with a “rash” of rust.

In a modern car, for example, the bumper is covered with a double layer (an underlayer of copper, and on top - chrome) and even a triple layer (copper - nickel - chrome). But this does not save the part from rust, since according to GOST and triple coating there are several pores per 1 cm2. What to do? The solution is to treat the surface of the coating special compounds, closing the pores.

Wipe the part with nickel (or other) coating with a slurry of magnesium oxide and water and immediately immerse it in a 50% solution of hydrochloric acid for 1...2 minutes.

After heat treatment, dip the part that has not yet cooled down into non-vitaminized fish oil (preferably old, unsuitable for its intended purpose).

Wipe the nickel-plated surface of the part 2...3 times with LPS (easily penetrating lubricant).

In the last two cases, excess fat (lubricant) is removed from the surface with gasoline after a day.

Large surfaces (bumpers, car moldings) are treated with fish oil as follows. In hot weather, wipe them with fish oil twice with a break of 12...14 hours. Then, after 2 days, excess fat is removed with gasoline.

The effectiveness of such processing is characterized by the following example. Nickel-plated fishing hooks begin to rust immediately after the first fishing in the sea. The same hooks treated with fish oil do not corrode almost all summer season sea ​​fishing.

Chrome plating

Chemical chrome plating allows you to obtain a gray coating on the surface of metal parts, which, after polishing, acquires the desired shine. Chrome fits well over nickel coating. The presence of phosphorus in chemically produced chromium significantly increases its hardness. Heat treatment for chrome coatings is necessary.

Below are practice-tested recipes for chemical chrome plating.

Compositions of solutions for chemical chromium plating (g/l)

Chromium fluoride - 14, sodium citrate - 7, acetic acid - 10 ml, sodium hypophosphite - 7. Solution temperature - 85...90°C, pH - 8...11, growth rate - 1.0...2 .5 µm/h.

Chromium fluoride - 16, chromium chloride - 1, sodium acetate - 10, sodium oxalate - 4.5, sodium hypophosphite - 10. Solution temperature - 75...90°C, pH - 4...6, growth rate - 2 ...2.5 µm/h.

Chromium fluoride - 17, chromium chloride - 1.2, sodium citrate - 8.5, sodium hypophosphite - 8.5. Solution temperature - 85...90°C, pH - 8...11, growth rate - 1...2.5 µm/h.

Chromium acetate - 30, nickel acetate - 1, sodium glycolic acid - 40, sodium acetate - 20, sodium citrate - 40, acetic acid - 14 ml, sodium hydroxide - 14, sodium hypophosphite - 15. Solution temperature - 99 ° C, pH - 4...6, growth rate - up to 2.5 µm/h.

Chromium fluoride - 5...10, chromium chloride - 5...10, sodium citrate - 20...30, sodium pyrophosphate (replacement of sodium hypophosphite) - 50...75.
Solution temperature - 100°C, pH - 7.5...9, growth rate - 2...2.5 µm/h.

Boron nickel plating

The film made from this dual alloy has increased hardness (especially after heat treatment), high temperature melting, high wear resistance and significant corrosion resistance. All this allows the use of such coating in various responsible homemade structures. Below are recipes for solutions in which boronickel plating is carried out.

Compositions of solutions for chemical boronickeling (g/l)

Nickel chloride - 20, sodium hydroxide - 40, ammonia (25% solution): - 11, sodium borohydride - 0.7, ethylenediamine (98% solution) - 4.5. The solution temperature is 97°C, the growth rate is 10 µm/h.

Nickel sulfate - 30, triethylsyntetramine - 0.9, sodium hydroxide - 40, ammonia (25% solution) - 13, sodium borohydride - 1. Solution temperature - 97 C, growth rate - 2.5 µm/h.

Nickel chloride - 20, sodium hydroxide - 40, Rochelle salt - 65, ammonia (25% solution) - 13, sodium borohydride - 0.7. The solution temperature is 97°C, the growth rate is 1.5 µm/h.

Caustic soda - 4...40, potassium metabisulfite - 1...1.5, sodium potassium tartrate - 30...35, nickel chloride - 10...30, ethylenediamine (50% solution) - 10...30 , sodium borohydride - 0.6...1.2. Solution temperature - 40...60°C, growth rate - up to 30 µm/h.

Solutions are prepared in the same way as for nickel plating: first, everything except sodium borohydride is dissolved, the solution is heated and sodium borohydride is dissolved.

Borocobaltation

The use of this chemical process makes it possible to obtain a film of particularly high hardness. It is used to repair friction pairs where increased wear resistance of the coating is required.

Compositions of solutions for boron cobaltation (g/l)

Cobalt chloride - 20, sodium hydroxide - 40, sodium citrate - 100, ethylenediamine - 60, ammonium chloride - 10, sodium borohydride - 1. Solution temperature - 60°C, pH - 14, growth rate - 1.5.. .2.5 µm/h.

Cobalt acetate - 19, ammonia (25% solution) - 250, potassium tartrate - 56, sodium borohydride - 8.3. Solution temperature - 50°C, pH - 12.5, growth rate - 3 µm/h.

Cobalt sulfate - 180, boric acid - 25, dimethylborazan - 37. Solution temperature - 18°C, pH - 4, growth rate - 6 µm/h.

Cobalt chloride - 24, ethylenediamine - 24, dimethylborazan - 3.5. Solution temperature - 70 C, pH - 11, growth rate - 1 µm/h.

The solution is prepared in the same way as boronickel.

Cadmium plating

On the farm, it is often necessary to use fasteners coated with cadmium. This is especially true for parts that are used outdoors.

It has been noted that chemically produced cadmium coatings adhere well to the base metal even without heat treatment.

Cadmium chloride - 50, ethylenediamine - 100. Cadmium must be in contact with the parts (suspension on cadmium wire, small parts are sprinkled with powdered cadmium). Solution temperature - 65°C, pH - 6...9, growth rate - 4 µm/h.

Attention! Ethylenediamine is the last to be dissolved in the solution (after heating).

Copper plating

Chemical copper plating is most often used in the manufacture printed circuit boards for radio electronics, in electroplating, for metallization of plastics, for double coating of some metals with others.

Compositions of solutions for copper plating (g/l)

Copper sulfate - 10, sulfuric acid - 10. Solution temperature - 15...25 ° C, growth rate - 10 µm/h.

Potassium sodium tartrate - 150, copper sulfate - 30, caustic soda - 80. Solution temperature - 15...25 ° C, growth rate - 12 µm/h.

Copper sulfate - 10...50, caustic soda - 10...30, Rochelle salt 40...70, formalin (40% solution) - 15...25. The solution temperature is 20°C, the growth rate is 10 µm/h.

Copper sulfate - 8...50, sulfuric acid - 8...50. The solution temperature is 20°C, the growth rate is 8 µm/h.

Copper sulfate - 63, potassium tartrate - 115, sodium carbonate - 143. Solution temperature - 20 C, growth rate - 15 µm/h.

Copper sulfate - 80...100, caustic soda - 80...,100, sodium carbonate - 25...30, nickel chloride - 2...4, Rochelle salt - 150...180, formalin (40% - nal solution) - 30...35. The solution temperature is 20°C, the growth rate is 10 µm/h. This solution makes it possible to obtain films with a low nickel content.

Copper sulfate - 25...35, sodium hydroxide - 30...40, sodium carbonate - 20-30, Trilon B - 80...90, formalin (40% solution) - 20...25, rhodanine - 0.003...0.005, potassium iron sulfide (red blood salt) - 0.1..0.15. Solution temperature - 18...25°C, growth rate - 8 µm/h.

This solution is highly stable over time and makes it possible to obtain thick films of copper.

To improve the adhesion of the film to the base metal, heat treatment is used the same as for nickel.

Silvering

Silvering metal surfaces, perhaps the most popular process among craftsmen, which they use in their activities. Dozens of examples can be given. For example, restoring the silver layer on cupronickel cutlery, silvering samovars and other household items.

For coiners, silvering, together with chemical coloring of metal surfaces (which will be discussed below), is a way to increase the artistic value of embossed paintings. Imagine a minted ancient warrior, whose chain mail and helmet are silvered.

The chemical silvering process itself can be carried out using solutions and pastes. The latter is preferable when processing large surfaces (for example, when silvering samovars or parts of large embossed paintings).

Composition of solutions for silver plating (g/l)

Silver chloride - 7.5, potassium iron sulfide - 120, potassium carbonate - 80. Working solution temperature - about 100°C. Processing time - until received required thickness layer of silver.

Silver chloride - 10, sodium chloride - 20, potassium tartrate - 20. Processing - in a boiling solution.

Silver chloride - 20, potassium ferric sulfide - 100, potassium carbonate - 100, ammonia (30% solution) - 100, sodium chloride - 40. Processing - in a boiling solution.

First, a paste is prepared from silver chloride - 30 g, tartaric acid - 250 g, sodium chloride - 1250, and everything is diluted with water until the consistency of sour cream. 10...15 g of paste is dissolved in 1 liter of boiling water. Processing - in a boiling solution.

The parts are hung in silvering solutions on zinc wires (strips).

Processing time is determined visually. It should be noted here that brass is better silvered than copper. A fairly thick layer of silver must be applied to the latter so that the dark copper does not show through the coating layer.

One more note. Solutions with silver salts cannot be stored for a long time, as this can form explosive components. The same applies to all liquid pastes.

Compositions of pastes for silvering.

In 300 ml warm water dissolve 2 g of lapis pencil (sold in pharmacies, it is a mixture of silver nitrate and amino acid potassium, taken in a ratio of 1:2 (by weight). A 10% solution of sodium chloride is gradually added to the resulting solution until the precipitation stops. Curdled sediment silver chloride is filtered and washed thoroughly in 5...6 waters.

20 g of sodium thiosulfite are dissolved in 100 ml of water. Silver chloride is added to the resulting solution until it stops dissolving. The solution is filtered and tooth powder is added to it until it reaches the consistency of liquid sour cream. Rub (silver) the part with this paste using a cotton swab.

Lapis pencil - 15, lemon acid(food) - 55, ammonium chloride - 30. Each component is ground into powder before mixing. Component content - in% (by weight).

Silver chloride - 3, sodium chloride - 3, sodium carbonate - 6, chalk - 2. Content of components - in parts (by weight).

Silver chloride - 3, sodium chloride - 8, potassium tartrate - 8, chalk - 4. Content of components - in parts (by weight).

Silver nitrate - 1, sodium chloride - 2. Content of components - in parts (by weight).

The last four pastes are used as follows. Finely ground components are mixed. Using a wet swab, dusting it with a dry mixture of chemical reagents, rub it (silver) the required part. The mixture is added all the time, constantly moistening the tampon.

When silvering aluminum and its alloys, the parts are first galvanized and then coated with silver.

Zincate treatment is carried out in one of the following solutions.

Compositions of solutions for zincate treatment (g/l)

For aluminum

Caustic soda - 250, zinc oxide - 55. Solution temperature - 20°C, processing time - 3...5 s.

Caustic soda - 120, zinc sulfate - 40. Solution temperature - 20°C, processing time - 1.5...2.0 minutes. To obtain a solution, first dissolve sodium hydroxide in one half of the water and zinc sulfate in the other. Then both solutions are poured together.

For duralumin

Caustic soda - 10, zinc oxide - 5, Rochelle salt - 10. Solution temperature - 20°C, processing time - 1...2 minutes.

After zincate treatment, the parts are silvered in any of the above solutions. However, the following solutions (g/l) are considered the best.

Silver nitrate - 100, ammonium fluoride - 100. Solution temperature - 20°C.

Silver fluoride - 100, ammonium nitrate - 100. Solution temperature - 20°C.

Tinning

Chemical tinning of the surfaces of parts is used as an anti-corrosion coating and as a preliminary process (for aluminum and its alloys) before soldering soft solders. Below are the compositions for tinning some metals.

Tinning compounds (g/l)

For steel

Tin chloride (fused) - 1, ammonia alum - 15. Tinning is carried out in a boiling solution, the growth rate is 5...8 µm/h.

Tin chloride - 10, aluminum ammonium sulfate - 300. Tinning is carried out in a boiling solution, the growth rate is 5 µm/h.

Tin chloride - 20, Rochelle salt - 10. Solution temperature - 80°C, growth rate - 3...5 µm/h.

Tin chloride - 3...4, Rochelle salt - until saturation. Solution temperature - 90...100°C, growth rate - 4...7 µm/h.

For copper and its alloys

Tin chloride - 1, potassium tartrate - 10. Tinning is carried out in a boiling solution, the growth rate is 10 µm/h.

Tin chloride - 20, sodium lactic acid - 200. Solution temperature - 20°C, growth rate - 10 µm/h.

Tin chloride - 8, thiourea - 40...45, sulfuric acid - 30...40. The solution temperature is 20°C, the growth rate is 15 µm/h.

Tin chloride - 8...20, thiourea - 80...90, hydrochloric acid - 6.5...7.5, sodium chloride - 70...80. Solution temperature - 50...100°C, growth rate - 8 µm/h.

Tin chloride - 5.5, thiourea - 50, tartaric acid - 35. Solution temperature - 60...70°C, growth rate - 5...7 µm/h.

When tinning parts made of copper and its alloys, they are hung on zinc hangers. Small parts“powdered” with zinc filings.

For aluminum and its alloys

Tinning of aluminum and its alloys is preceded by some additional processes. First, parts degreased with acetone or gasoline B-70 are treated for 5 minutes at a temperature of 70 ° C with the following composition (g/l): sodium carbonate - 56, sodium phosphate - 56. Then the parts are immersed for 30 s in a 50% solution of nitric acid. acid, rinse thoroughly under running water and immediately place in one of the solutions (for tinning) given below.

Sodium stannate - 30, sodium hydroxide - 20. Solution temperature - 50...60°C, growth rate - 4 µm/h.

Sodium stannate - 20...80, potassium pyrophosphate - 30...120, caustic soda - 1.5..L.7, ammonium oxalate - 10...20. Solution temperature - 20...40°C, growth rate - 5 µm/h.

Removing metal coatings

Typically, this process is necessary to remove low-quality metal films or to clean any metal product being restored.

All of the solutions below work faster at elevated temperatures.

Compositions of solutions for removing metal coatings in parts (by volume)

For steel removing nickel from steel

Nitric acid - 2, sulfuric acid - 1, iron sulfate (oxide) - 5...10. The temperature of the mixture is 20°C.

Nitric acid - 8, water - 2. Solution temperature - 20 C.

Nitric acid - 7, acetic acid (glacial) - 3. Mixture temperature - 30°C.

To remove nickel from copper and its alloys (g/l)

Nitrobenzoic acid - 40...75, sulfuric acid - 180. Solution temperature - 80...90 C.

Nitrobenzoic acid - 35, ethylenediamine - 65, thiourea - 5...7. The solution temperature is 20...80°C.

To remove nickel from aluminum and its alloys, commercial nitric acid is used. Acid temperature - 50°C.

To remove copper from steel

Nitrobenzoic acid - 90, diethylenetriamine - 150, ammonium chloride - 50. Solution temperature - 80°C.

Sodium pyrosulfate - 70, ammonia (25% solution) - 330. Solution temperature - 60°.

Sulfuric acid - 50, chromic anhydride - 500. Solution temperature - 20°C.

For removing copper from aluminum and its alloys (with zincate treatment)

Chromic anhydride - 480, sulfuric acid - 40. Solution temperature - 20...70°C.

Technical nitric acid. The solution temperature is 50°C.

To remove silver from steel

Nitric acid - 50, sulfuric acid - 850. Temperature - 80°C.

Technical nitric acid. Temperature - 20°C.

Silver is removed from copper and its alloys using technical nitric acid. Temperature - 20°C.

Chrome is removed from steel with a solution of caustic soda (200 g/l). The solution temperature is 20 C.

Chromium is removed from copper and its alloys with 10% hydrochloric acid. The solution temperature is 20°C.

Zinc is removed from steel with 10% hydrochloric acid - 200 g/l. The solution temperature is 20°C.

Zinc is removed from copper and its alloys with concentrated sulfuric acid. Temperature - 20 C.

Cadmium and zinc are removed from any metals with a solution of aluminum nitrate (120 g/l). The solution temperature is 20°C.

Tin is removed from steel with a solution containing sodium hydroxide - 120, nitrobenzoic acid - 30. Solution temperature - 20°C.

Tin is removed from copper and its alloys in a solution of ferric chloride - 75...100, copper sulfate - 135...160, acetic acid (glacial) - 175. solution temperature - 20°C.

Chemical oxidation and coloring of metals

Chemical oxidation and painting of the surface of metal parts are intended to create an anti-corrosion coating on the surface of the parts and enhance the decorative effect of the coating.

In ancient times, people already knew how to oxidize their crafts, changing their color (blackening silver, painting gold, etc.), burnishing steel objects (heating a steel part to 220...325°C, they lubricated it with hemp oil).

Compositions of solutions for oxidizing and painting steel (g/l)

Note that before oxidation, the part is ground or polished, degreased and pickled.

Black color

Caustic soda - 750, sodium nitrate - 175. Solution temperature - 135°C, processing time - 90 minutes. The film is dense and shiny.

Caustic soda - 500, sodium nitrate - 500. Solution temperature - 140°C, processing time - 9 minutes. The film is intense.

Caustic soda - 1500, sodium nitrate - 30. Solution temperature - 150°C, processing time - 10 minutes. The film is matte.

Caustic soda - 750, sodium nitrate - 225, sodium nitrate - 60. Solution temperature - 140°C, treatment time - 90 minutes. The film is shiny.

Calcium nitrate - 30, orthophosphoric acid - 1, manganese peroxide - 1. Solution temperature - 100°C, processing time - 45 minutes. The film is matte.

All of the above methods are characterized by a high operating temperature of the solutions, which, of course, does not allow processing large-sized parts. However, there is one “low-temperature solution” suitable for this purpose (g/l): sodium thiosulfate - 80, ammonium chloride - 60, orthophosphoric acid - 7, nitric acid - 3. Solution temperature - 20 ° C, processing time - 60 min . The film is black, matte.

After oxidizing (blackening) the steel parts, they are treated for 15 minutes in a solution of potassium chromium (120 g/l) at a temperature of 60°C.

Then the parts are washed, dried and coated with any neutral machine oil.

Blue

Hydrochloric acid - 30, ferric chloride- 30, mercury nitrate - 30, ethanol- 120. Solution temperature - 20...25°C, processing time - up to 12 hours.

Sodium hydrosulfide - 120, lead acetate - 30. Solution temperature - 90...100°C, processing time - 20...30 minutes.

Blue color

Lead acetate - 15...20, sodium thiosulfate - 60, acetic acid (glacial) - 15...30. The solution temperature is 80°C. Processing time depends on the color intensity.

Compositions of solutions for oxidation and coloring of copper (g/l)

Bluish-black colors

Caustic soda - 600...650, sodium nitrate - 100...200. Solution temperature - 140°C, treatment time - 2 hours.

Caustic soda - 550, sodium nitrate - 150...200. Solution temperature - 135...140°C, processing time - 15...40 minutes.

Caustic soda - 700...800, sodium nitrate - 200...250, sodium nitrate -50...70. Solution temperature - 140...150°C, processing time - 15...60 minutes.

Caustic soda - 50...60, potassium persulfate - 14...16. Solution temperature - 60...65 C, processing time - 5...8 minutes.

Potassium sulfide - 150. Solution temperature - 30°C, processing time - 5...7 minutes.

In addition to the above, a solution of the so-called sulfur liver is used. Sulfur liver is obtained by fusing 1 part (by weight) of sulfur with 2 parts of potassium carbonate (potash) in an iron can for 10...15 minutes (with stirring). The latter can be replaced with the same amount of sodium carbonate or sodium hydroxide.

The glassy mass of liver sulfur is poured onto an iron sheet, cooled and crushed to powder. Store sulfur liver in an airtight container.

A solution of liver sulfur is prepared in an enamel container at the rate of 30...150 g/l, the temperature of the solution is 25...100°C, the processing time is determined visually.

In addition to copper, a solution of sulfur liver can blacken silver well and satisfactorily blacken steel.

Green color

Copper nitrate - 200, ammonia (25% solution) - 300, ammonium chloride - 400, sodium acetate - 400. Solution temperature - 15...25°C. The color intensity is determined visually.

Brown color

Potassium chloride - 45, nickel sulfate - 20, copper sulfate - 100. Solution temperature - 90...100 ° C, color intensity is determined visually.

Brownish yellow color

Caustic soda - 50, potassium persulfate - 8. Solution temperature - 100°C, processing time - 5...20 minutes.

Blue

Sodium thiosulfate - 160, lead acetate - 40. Solution temperature - 40...100°C, processing time - up to 10 minutes.

Compositions for oxidizing and painting brass (g/l)

Black color

Copper carbonate - 200, ammonia (25% solution) - 100. Solution temperature - 30...40°C, processing time - 2...5 minutes.

Copper bicarbonate - 60, ammonia (25% solution) - 500, brass (sawdust) - 0.5. Solution temperature - 60...80°C, processing time - up to 30 minutes.

Brown color

Potassium chloride - 45, nickel sulfate - 20, copper sulfate - 105. Solution temperature - 90...100 ° C, processing time - up to 10 minutes.

Copper sulfate - 50, sodium thiosulfate - 50. Solution temperature - 60...80 ° C, processing time - up to 20 minutes.

Sodium sulfate - 100. Solution temperature - 70°C, processing time - up to 20 minutes.

Copper sulfate - 50, potassium permanganate - 5. Solution temperature - 18...25 ° C, processing time - up to 60 minutes.

Blue

Lead acetate - 20, sodium thiosulfate - 60, acetic acid (essence) - 30. Solution temperature - 80°C, treatment time - 7 minutes.

3green color

Nickel ammonium sulfate - 60, sodium thiosulfate - 60. Solution temperature - 70...75 ° C, processing time - up to 20 minutes.

Copper nitrate - 200, ammonia (25% solution) - 300, ammonium chloride - 400, sodium acetate - 400. Solution temperature - 20°C, treatment time - up to 60 minutes.

Compositions for oxidizing and painting bronze (g/l)

Green color

Ammonium chloride - 30, 5% acetic acid - 15, copper acetic acid - 5. Solution temperature - 25...40°C. Hereinafter, the intensity of bronze color is determined visually.

Ammonium chloride - 16, acidic potassium oxalate - 4, 5% acetic acid - 1. Solution temperature - 25...60°C.

Copper nitrate - 10, ammonium chloride - 10, zinc chloride - 10. Solution temperature - 18...25°C.

Yellow- green color

Copper nitrate - 200, sodium chloride - 20. Solution temperature - 25°C.

Blue to yellow-green

Depending on the processing time, it is possible to obtain colors from blue to yellow-green in a solution containing ammonium carbonate - 250, ammonium chloride - 250. Solution temperature - 18...25°C.

Patination (giving the appearance of old bronze) is carried out in the following solution: liver sulfur - 25, ammonia (25% solution) - 10. Solution temperature - 18...25°C.

Compositions for oxidizing and coloring silver (g/l)

Black color

Sulfur liver - 20...80. Solution temperature - 60..70°C. Here and below, the color intensity is determined visually.

Ammonium carbonate - 10, potassium sulfide - 25. Solution temperature - 40...60°C.

Potassium sulfate - 10. Solution temperature - 60°C.

Copper sulfate - 2, ammonium nitrate - 1, ammonia (5% solution) - 2, acetic acid (essence) - 10. Solution temperature - 25...40°C. The content of components in this solution is given in parts (by weight).

Brown color

Ammonium sulfate solution - 20 g/l. The solution temperature is 60...80°C.

Copper sulfate - 10, ammonia (5% solution) - 5, acetic acid - 100. Solution temperature - 30...60°C. The content of components in the solution is in parts (by weight).

Copper sulfate - 100, 5% acetic acid - 100, ammonium chloride - 5. Solution temperature - 40...60°C. The content of components in the solution is in parts (by weight).

Copper sulfate - 20, potassium nitrate - 10, ammonium chloride - 20, 5% acetic acid - 100. Solution temperature - 25...40°C. The content of components in the solution is in parts (by weight).

Blue

Liver sulfur - 1.5, ammonium carbonate - 10. Solution temperature - 60°C.

Liver sulfur - 15, ammonium chloride - 40. Solution temperature - 40...60°C.

Green color

Iodine - 100, hydrochloric acid - 300. Solution temperature - 20°C.

Iodine - 11.5, potassium iodide - 11.5. The solution temperature is 20°C.

Attention! When dyeing silver green, you must work in the dark!

Composition for oxidizing and painting nickel (g/l)

Nickel can only be painted black. The solution (g/l) contains: ammonium persulfate - 200, sodium sulfate - 100, iron sulfate - 9, ammonium thiocyanate - 6. Solution temperature - 20...25 ° C, processing time - 1-2 minutes.

Compositions for the oxidation of aluminum and its alloys (g/l)

Black color

Ammonium molybdate - 10...20, ammonium chloride - 5...15. Solution temperature - 90...100°C, processing time - 2...10 minutes.

Grey colour

Arsenic trioxide - 70...75, sodium carbonate - 70...75. The solution temperature is boiling, the processing time is 1...2 minutes.

Green color

Orthophosphoric acid - 40...50, acidic potassium fluoride - 3...5, chromic anhydride - 5...7. Solution temperature - 20...40 C, processing time - 5...7 minutes.

Orange color

Chromic anhydride - 3...5, sodium fluorosilicate - 3...5. Solution temperature - 20...40°C, processing time - 8...10 minutes.

Yellow-brown color

Sodium carbonate - 40...50, sodium chloride - 10...15, caustic soda - 2...2.5. Solution temperature - 80...100°C, processing time - 3...20 minutes.

Protective compounds

Often a craftsman needs to process (paint, coat with another metal, etc.) only part of the craft, and leave the rest of the surface unchanged.
To do this, the surface that does not need to be coated is painted over with a protective composition that prevents the formation of one or another film.

The most affordable, but not heat-resistant protective coatings- waxy substances (wax, stearin, paraffin, ceresin) dissolved in turpentine. To prepare such a coating, wax and turpentine are usually mixed in a ratio of 2:9 (by weight). This composition is prepared as follows. The wax is melted in a water bath and warm turpentine is added to it. To protective composition would be contrasting (its presence could be clearly seen and controlled), a small amount of dark-colored paint soluble in alcohol is introduced into the composition. If this is not available, it is not difficult to add a small amount of dark shoe cream to the composition.

You can give a more complex recipe, % (by weight): paraffin - 70, beeswax - 10, rosin - 10, pitch varnish (kuzbasslak) - 10. All ingredients are mixed, melted over low heat and mixed thoroughly.

Waxy protective compounds are applied hot with a brush or swab. All of them are designed for operating temperatures no higher than 70°C.
Protective compounds based on asphalt, bitumen and pitch varnishes have somewhat better heat resistance (operating temperature up to 85°C). They are usually liquefied with turpentine in a ratio of 1:1 (by weight). Cold composition applied to the surface of the part with a brush or swab. Drying time - 12...16 hours.

Perchlorovinyl paints, varnishes and enamels can withstand temperatures up to 95°C, oil-bitumen varnishes and enamels, asphalt-oil and bakelite varnishes - up to 120°C.

The most acid-resistant protective composition is a mixture of glue 88N (or “Moment”) and filler (porcelain flour, talc, kaolin, chromium oxide), taken in the ratio: 1:1 (by weight). The required viscosity is obtained by adding to the mixture a solvent consisting of 2 parts (by volume) B-70 gasoline and 1 part ethyl acetate (or butyl acetate). The operating temperature of such a protective composition is up to 150 C.

A good protective composition is epoxy varnish (or putty). Operating temperature - up to 160°C.

Nickel is a metal of the iron subgroup, which is most widely used in electroplating.

Compared to copper plating, brass plating, silver plating, etc., nickel plating received industrial application much later, but since the end of the 19th century, this process has become the most common method of “refining” the surface of metal products. It was only in the twenties of this century that another process, chrome plating, became widely used, which seemed to replace nickel plating. However, both of these processes - nickel plating and chrome plating for protective and decorative purposes are used in combination, i.e. the products are first nickel-plated and then coated thin layer chromium (tenths of a micron). The role of nickel coating is not diminished; on the contrary, increased demands are placed on it.

The widespread use of nickel plating in electroplating is explained by the valuable physical and chemical properties of electrolytically deposited nickel. Although in a number of voltages nickel is higher than hydrogen, due to a strong tendency to passivation, it turns out to be quite resistant to atmospheric air, alkalis and some acids. In relation to iron, nickel has a less electronegative potential; therefore, the base metal - iron - is protected by nickel from corrosion only if there are no pores in the coating.

Nickel coatings obtained from solutions of simple salts have a very fine structure, and since at the same time electrolytic nickel easily accepts polishing, the coatings can be brought to a mirror shine. This circumstance allows the widespread use of nickel coatings for decorative purposes. By introducing brightening agents into the electrolyte, it is possible to obtain shiny nickel coatings in layers of sufficient thickness without polishing. The structure of normal nickel deposits is extremely fine and difficult to detect even under high magnification.

Most often, nickel plating serves two purposes: protecting the base metal from corrosion and decorative surface finishing. Such coatings are widely used for the external parts of cars, bicycles, various apparatus, instruments, surgical instruments, household items, etc.

From an electrochemical point of view, nickel can be characterized as a representative of the iron group metals. In a strongly acidic environment, the deposition of these metals is generally impossible - almost only hydrogen is released at the cathode. Moreover, even in solutions close to neutral, changes in pH affect the current efficiency and properties of metal deposits.

The phenomenon of sediment peeling, which is most characteristic of nickel, is also strongly associated with the acidity of the environment. Hence the primary concern is maintaining the proper acidity and regulating it during nickel plating, as well as choosing the proper temperature for the correct conduct of the process.

The first electrolytes for nickel plating were based on the double salt NiSO 4 (NH 4) 2 SO 4 6H 2 O. These electrolytes were first studied and developed by Harvard University professor Isaac Adams in 1866. Compared to modern high-performance electrolytes with a high concentration of nickel salt double salt electrolytes allow a current density not exceeding 0.3-0.4 A/dm 2 . The solubility of double nickel salt at room temperature does not exceed 60-90 g/l, while nickel sulfate heptahydrate at room temperature dissolves in an amount of 270-300 g/l. The content of metallic nickel in the double salt is 14.87%, and in the simple (sulfate) salt 20.9%.

The nickel plating process is very sensitive to impurities in the electrolyte and anodes. It is quite obvious that a salt that is slightly soluble in water is easier to free from harmful impurities, such as sulfates of copper, iron, zinc, etc., during the process of crystallization and washing, than a more soluble simple salt. Largely for this reason, double salt electrolytes had dominant use in the second half of the 19th and early 20th centuries.

Boric acid, which is now considered a very important component for buffering the nickel plating electrolyte and electrolytic refining of nickel, was first proposed in the late 19th and early 20th centuries.

Chlorides were proposed for activating nickel anodes at the beginning of the 20th century. To date, a wide variety of electrolytes and modes for nickel plating have been proposed in patent and journal literature, apparently more than for any other metal electrodeposition process. However, it can be said without exaggeration that most modern electrolytes for nickel plating are a variation of those proposed in 1913 by Watts, a professor at the University of Wisconsin, based on a detailed study of the influence of individual components and electrolyte conditions. Somewhat later, as a result of improvements, he found that in electrolytes concentrated in nickel, at elevated temperatures and intense stirring (1000 rpm), it is possible to obtain satisfactory nickel coatings in thick layers at a current density exceeding 100 A/dm 2 (for simple products forms). These electrolytes consist of three main components: nickel sulfate, nickel chloride and boric acid. It is fundamentally possible to replace nickel chloride with sodium chloride, but, according to some data, such a replacement somewhat reduces the permissible cathode current density (possibly due to a decrease in the total concentration of nickel in the electrolyte). Watts electrolyte has the following composition, g/l:
240 - 340 NiSO 4 7H 2 O, 30-60 NiCl 2 6H 2 O, 30 - 40 H 3 BO 3.

Other electrolytes that have recently increasingly attracted the attention of researchers and are finding industrial application include fluoroborate electrolytes, which allow the use of increased current density, and sulfamate electrolytes, which make it possible to obtain nickel coatings with lower internal voltages.

In the early thirties of the current century, and especially after the Second World War, the attention of researchers was focused on the development of such brightening agents that make it possible to obtain shiny nickel coatings in layers of sufficient thickness not only on the surface of the base metal polished to a shine, but also on a matte surface.

The discharge of nickel ions, like other metals of the iron subgroup, is accompanied by significant chemical polarization and the release of these metals at the cathode begins at potential values ​​that are much more negative than the corresponding standard potentials.

Much research has been devoted to understanding the reasons for this increased polarization, and several conflicting explanations have been proposed. According to some data, cathodic polarization during the electrodeposition of metals of the iron group is sharply expressed only at the moment of their precipitation; with a further increase in the current density, the potentials change slightly. With increasing temperature, the cathodic polarization (at the moment the precipitation begins) sharply decreases. Thus, at the moment of the beginning of nickel precipitation at a temperature of 15°C, the cathodic polarization is 0.33 V, and at 95°C 0.05 V; for iron, cathodic polarization decreases from 0.22 V at 15 ° C to zero at 70 ° C, and for cobalt from 0.25 V at 15 ° C to 0.05 V at 95 ° C.

The high cathodic polarization at the beginning of the release of iron group metals was explained by the release of these metals in a metastable form and the need to consume extra energy to move them to steady state. This explanation is not generally accepted; there are other views on the reasons for the large cathodic polarization, during which the iron group metals are released, and the fine-crystalline structure associated with polarization.

Other followers attributed a special role to the hydrogen film formed as a result of the joint discharge of hydrogen ions, complicating the process of aggregation of small crystals and leading to the formation of finely dispersed deposits of iron group metals, as well as alkalization of the cathode layer and the associated precipitation of colloidal hydroxides and basic salts, which can co-precipitate with metals and impede the growth of crystals.

Some assumed that the high polarization of metals of the iron group is associated with a high activation energy during the discharge of highly hydrated ions; calculations of others showed that the energy of dehydration of metals of the iron group is approximately the same as the energy of dehydration of such divalent metal ions as copper, zinc, cadmium, the discharge of ions proceeds with insignificant cathodic polarization, approximately 10 times less than during the electrodeposition of iron, cobalt, and nickel. The increased polarization of iron group metals was and is now explained by the adsorption of foreign particles; polarization decreased noticeably with continuous cleaning of the cathode surface.

This does not exhaust the review of different views on the reasons for increased polarization during the electrodeposition of iron group metals. It can, however, be accepted that, with the exception of the region of low concentrations and high densities current, the kinetics of these processes can be described by the equation of the slow discharge theory.

Due to the large cathodic polarization with a relatively small hydrogen overvoltage, the processes of electrodeposition of iron group metals are extremely sensitive to the concentration of hydrogen ions in the electrolyte and to temperature. The higher the temperature and the concentration of hydrogen ions (the lower the hydrogen index), the higher the permissible cathode current density.