N - nickel plating. Nickel plating at home (chemical and galvanic) Nickel solution

The property of nickel to create a thin oxide film on its surface, resistant to acids and alkalis, allows it to be used for anti-corrosion protection of metals.

The main method used in industry is galvanic nickel plating, but it requires quite complex equipment and involves working with acids and alkalis, the vapors of which are released during operation and can greatly harm human health. The chemical method can be used to coat steel, aluminum, brass, bronze and other metals as it is easy to use and the process can be done at home.

Today, there are two main methods of coating metal parts with nickel: galvanic and chemical. The first method requires a source direct current- electrolytic bath with electrodes and a large number of chemical reagents. The second method is much simpler. To carry it out, you need to have measuring vessels and an enamel container for heating the reagents. Despite all the apparent simplicity, this is a rather complex process that requires a lot of attention and compliance with safety rules. If possible, carry out reactions in a well-ventilated area. Ideal option The workplace will be equipped with an exhaust hood, in no case connected to the general house ventilation. When working, use safety glasses and do not leave the container with reagents unattended.

Nickel coating of metal parts

The main stages for chemical nickel plating are as follows:

1. In order for the nickel to cover the surface with a thin and uniform layer, the product is first ground and polished.
2. Degreasing. Since even the thinnest film of fat on the surface of the workpiece can cause uneven distribution of nickel over the area of ​​the part, the latter is degreased in a special solution consisting of 25-35 g/l NaOH or KOH, 30-60 g of soda ash and 5-10 g of liquid glass.
3. The part or product that needs to be plated with nickel is washed in water and then immersed in a 5% HCl solution for 0.5-1 minute. This step is taken in order to remove a thin layer of oxides from the metal surface, which will significantly reduce adhesion between materials. After pickling, the part is rinsed again in water, then immediately transferred to a container of nickel plating solution.

Nickel plating itself is carried out by boiling a metal product in a special solution, which is prepared as follows:

• take water (preferably distilled) at the rate of 300 ml/dm 2 of the surface area of ​​the part, including both internal and external;
• the water is heated to 60°C, after which 30 g of nickel chloride (NiCl 2) and 10 g of sodium acetate (CH 3 COONa) are dissolved in it per 1 liter of water;
• the temperature is raised to 80°C and 15 g of sodium hyposulfite is added, then the workpiece is immersed in a container with the solution.

Boiling a metal product

After immersing the part, the solution is heated to 90-95°C and the temperature is maintained at this level throughout the entire nickel plating process. If you see that the amount of solution has decreased significantly, you can add preheated distilled water to it. Boiling should take at least 1-2 hours. Sometimes, to obtain a multilayer coating, metal products are subjected to a series of short (20-30 minutes) boilings, after each of which the part is removed from the solution, washed and dried. This makes it possible to obtain a nickel layer from 3-4 layers, which in total have greater density and quality than a single layer of the same thickness.

The peculiarity of the coating of steel products is that nickel is deposited spontaneously due to the catalytic effect of iron. To deposit a protective layer on non-ferrous metals, a different composition is used.

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Chemical nickel plating of non-ferrous metals allows you to create protective film on the surface of brass, copper and bronze. To do this, the part is first degreased with a solution, the composition of which is indicated in the first method, and it is not necessary to remove the oxide film from the metal. The solution for nickel plating is prepared as follows: a 10% solution of zinc chloride (ZnCl 2), which is better known as “soldering acid,” is poured into an enamel container. Nickel sulfate (NiSO 4) is gradually added to it to such a concentration at which the solution is colored green color. The composition is brought to a boil, after which the part is immersed in it for 1.5-2 hours. After the reaction is completed, the product is removed from the solution and placed in a container with chalk water (prepared by adding 50-70 g of chalk powder per 1 liter of water), and then washed.

Nickel sulfate solution

Nickel plating of aluminum uses a similar technology, but the composition of the solution is slightly different:

• 20 g nickel sulfate;
• 10 g sodium acetate;
• 25 g sodium hypophosphorate;
• 3 ml of thiourea with a concentration of 1 g/l;
• 0.4 g sodium fluoride;
• 9 ml acetic acid.

Machining of aluminum parts

Before processing, aluminum products are immersed in a caustic soda solution with a concentration of 10-15% and heated to a temperature of 60-70°C. In this case, a violent reaction occurs with the release of hydrogen, the bubbles of which clean the surface of oxides and contamination. Depending on the degree of contamination, the parts are kept in the cleaning solution from 15-20 seconds to 1-2 minutes, after which they are washed in running water and immersed in a nickel-plating solution.

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Due to nickel plating, the physical, mechanical and decorative properties metal products. Nickel has a silvery-white color; in air it quickly becomes covered with a film of oxides invisible to the human eye, which practically does not change it appearance, but at the same time reliably protect against further oxidation and reactions with an aggressive environment. Nickel plating is used to protect steel, bronze, brass, aluminum, copper and other materials.

Protection of metal products from oxidation

Is cathodic protection. This means that if the integrity of the coating is damaged, the metal begins to react with external environment. To increase the mechanical properties of the protective layer, you need to apply it strictly following the technology and sequence of actions. Nickel applied to a surface with traces of contamination and rust, with a large number of irregularities, may begin to swell and peel off during use.

Products coated with nickel are almost in no way inferior to chrome plated - they have a similar shine and hardness. At large sizes containers for chemical reaction Nickel can be used to coat fairly large parts, such as car wheels.

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Nickel plating gives the metal a beautiful shiny appearance, high corrosion resistance and increases surface hardness. Nickel-plated parts can be used to decorate fence posts, if the site design provides for one. Various hardware - fastening bolts, brackets, elements - look beautiful and have a long service life furniture fittings. They can be used in conditions high humidity, temperature and load - in places where steel quickly rusts and loses its properties.

Electroless nickel plating can be done with your own hands, in a well-ventilated garage or workshop.

Beautiful shiny surface appearance

It is not advisable to perform the described technological operations in the kitchen, since fumes from any chemical substances can be hazardous to health.

Nickel plating using chemical reagents does not require high energy consumption, unlike galvanic plating, but allows you to obtain a fairly high-quality, shiny and hard coating.

We moved to new office- neighboring building. Pay attention to the directions in the contacts section.

We temporarily do not apply vacuum coatings

Due to the modernization of the vacuum coating section, we are temporarily not performing vacuum coating work.

ISO 9000 Certificate

The quality management system at our enterprise complies with ISO 9000

Application of titanium nitride

We vacuum-spray titanium nitride (TiN) onto products with dimensions up to 2500x2500x2500 mm.

Brass plating and bronzing

It became possible to carry out work on decorative application brass and bronze

Good news! We moved!

In connection with the long-awaited expansion of production, we moved to a new site in Balashikha. For your convenience, it is now possible to pick up/delivery parts using our vehicles!

Partners

N - Nickel plating

• Coating codes: N, N.b., Khim.N.tv, Khim.N, N.m.ch.
• Processed steels: any, including aluminum and titanium alloys
• Product dimensions: up to 1000x1000x1000 mm. Weight up to 3 tons.
• Coating of products of any complexity
• Quality control department, quality certificate, work within the framework of the state defense order

general information

Nickel plating is a process of electroplating or chemical deposition of nickel with a thickness of 1 micron to 100 microns.
Nickel coatings have high corrosion resistance, high hardness and good decorative properties.

Nickel melting point: 1445° C
Microhardness of nickel coatings: up to 500 HV (chemical 800 HV)

The applications of nickel-plated parts depend on whether the nickel coating is used as a finishing coating, or whether the nickel coating acts as a sublayer (substrate) for the application of other electroplating coatings.
Nickel coatings can be applied to almost all metals.

The main areas of application of galvanic and chemical nickel plating:

Use of nickel as an independent coating

• For decorative purposes.
  Nickel coatings have a good mirror shine and practically do not fade in air. The coatings withstand operation well in atmospheric conditions due to their high corrosion resistance. Often plated with nickel decorative items, fencing, equipment and tools.
• For technical purposes.
  For protection against corrosion of electrical contacts or mechanisms operating in a humid environment, as well as as a coating for soldering. The black nickel plating process has become widespread in the optical industry.

Use of nickel in combination with other electroplating coatings

• When applying multilayer protective and decorative coatings.
  Typically in combination with copper and chromium (copper plating, nickel plating, chromium plating) and other metals as an intermediate layer to increase the shine of the chrome plating, as well as for corrosion protection and to prevent copper from diffusion through the pores of the chromium to the surface, which can lead to a short time to the appearance of red spots on the chrome plating.

Examples of nickel-plated parts

Nickel plating technology

During electrochemical deposition of nickel on the cathode, two main processes occur: Ni 2+ + 2e - → Ni and 2Н + + 2е - → Н 2.

As a result of the discharge of hydrogen ions, their concentration in the near-cathode layer decreases, i.e., the electrolyte becomes alkalized. In this case, basic nickel salts can form, which affect the structure and mechanical properties of the nickel coating. The release of hydrogen also causes pitting - a phenomenon in which hydrogen bubbles, lingering on the surface of the cathode, prevent the discharge of nickel ions in these places. Pits form on the coating and the sediment loses its decorative appearance.

To combat pitting, substances are used that reduce the surface tension at the metal-solution interface.

During anodic dissolution, nickel is easily passivated. When passivating anodes in the electrolyte, the concentration of nickel ions decreases and the concentration of hydrogen ions quickly increases, which leads to a drop in current efficiency and deterioration in the quality of the deposits. To prevent passivation of anodes, activators are introduced into nickel plating electrolytes. Such activators are chlorine ions, which are introduced into the electrolyte in the form of nickel chloride or sodium chloride.

Nickel sulfate electrolytes are most widely used. These electrolytes are stable in operation, with correct operation they can be used for several years without replacement. Composition of some electrolytes and nickel plating modes:

Sodium sulfate and magnesium sulfate are introduced into the electrolyte to increase the electrical conductivity of the solution. The conductivity of sodium solutions is higher, but in the presence of magnesium sulfate, lighter, softer and more easily polished deposits are obtained.

Nickel electrolyte is very sensitive to even small changes in acidity. To maintain the pH value within the required limits, it is necessary to use buffer compounds. As such a compound that prevents a rapid change in the acidity of the electrolyte, it is used boric acid.

To facilitate the dissolution of the anodes, sodium chloride salts are introduced into the bath.

To prepare nickel plating sulfate electrolytes, it is necessary to dissolve them in separate containers in hot water all components. After settling, the solutions are filtered into working bath. The solutions are mixed, the pH of the electrolyte is checked and, if necessary, adjusted with a 3% sodium hydroxide solution or a 5% sulfuric acid solution. Then the electrolyte is adjusted with water to the required volume.

If there are impurities, it is necessary to work on the electrolyte before using it, since nickel electrolytes are extremely sensitive to foreign impurities, both organic and inorganic.
Defects during the operation of bright nickel plating electrolyte and methods for eliminating them are given in Table 1.

Table 1. Defects during operation of sulfuric acid electrolytes of nickel plating and methods for their elimination

When nickel plating, hot-rolled anodes are used, as well as non-passivable anodes. Anodes in the form of plates (cards) are also used, which are loaded into covered titanium baskets. Card anodes promote uniform dissolution of nickel. To avoid contamination of the electrolyte with anode sludge, nickel anodes should be enclosed in fabric covers, which are pre-treated with a 2-10% solution of hydrochloric acid.
The ratio of the anodic surface to the cathodic surface during electrolysis is 2:1.

Nickel plating small parts carried out in bell and drum baths. When nickel plating in bell baths, an increased content of chloride salts in the electrolyte is used to prevent passivation of the anodes, which can occur due to a mismatch between the surfaces of the anodes and cathodes, as a result of which the concentration of nickel in the electrolyte decreases and the pH value decreases. It can reach such limits that the deposition of nickel stops altogether. A disadvantage when working in bells and drums is also the large carryover of electrolyte with parts from the baths. The specific loss rates range from 220 to 370 ml/m2.

For the protective and decorative finishing of parts, shiny and mirror nickel coatings obtained directly from electrolytes with shine-forming additives are widely used. Electrolyte composition and nickel plating mode:

Nickel sulfate - 280-300 g/l
Nickel chloride - 50-60 g/l
Boric acid - 25-40 g/l
Saccharin 1-2 g/l
1,4-butynediol - 0.15-0.18 ml/l
Phthalimid 0.02-0.04 g/l
pH = 4-4.8
Temperature = 50-60°C
Current density = 3-8 A/dm2

To obtain shiny nickel coatings, electrolytes with other brightening additives are also used: chloramine B, propargyl alcohol, benzosulfamide, etc.
When applying a shiny coating, intensive mixing of the electrolyte with compressed air is necessary, preferably in combination with swinging the cathode rods, as well as continuous filtration of the electrolyte,
The electrolyte is prepared as follows. In distilled or deionized hot (80-90°C) water, dissolve nickel sulfate, nickel chloride, and boric acid with stirring. The electrolyte brought to the working volume with water is subjected to chemical and selective purification.

To remove copper and zinc, the electrolyte is acidified with sulfuric acid to pH 2-3, large area cathodes made of corrugated steel are hung and the electrolyte is processed for 24 hours at a temperature of 50-60 ° C, stirring with compressed air. Current density 0.1-0.3 A/dm2. Then the pH of the solution is adjusted to 5.0-5.5, after which potassium permanganate (2 g/l) or a 30% solution of hydrogen peroxide (2 ml/l) is introduced into it.
The solution is stirred for 30 minutes, add 3 g/l activated carbon, treated with sulfuric acid, and mix the electrolyte 3-4 using compressed air. The solution settles for 7-12 hours, then filters into the working bath.

Brightening agents are introduced into the purified electrolyte: saccharin and 1,4-butynediol directly, phthalimide - pre-dissolved in a small amount of electrolyte heated to 70-80 ° C. The pH is adjusted to the required value and work begins. The consumption of brightening agents when adjusting the electrolyte is: saccharin 0.01-0.012 g/(Ah); 1,4-butindiol (35% solution) 0.7-0.8 ml/(Ah); phthalimide 0.003-0.005 g/(Ah).
Defects during the operation of bright nickel plating electrolyte and methods for eliminating them are given in Table 2.

Table 2. Defects during operation of bright nickel plating electrolyte and methods for eliminating them

Multilayer nickel plating is used to increase the corrosion resistance of nickel coatings compared to single-layer coatings.
This is achieved by sequential deposition of nickel layers from several electrolytes with different physical and chemical properties of the coating. Multilayer nickel coatings include: bi-nickel, tri-nickel, sil-nickel.

The corrosion resistance of bi-nickel coatings is 1.5-2 notches higher than single-layer coatings. It is advisable to use them instead of single-layer matte and shiny nickel coatings.

To achieve high corrosion resistance, the first layer of nickel (matte or semi-shiny), constituting at least 1/2 - 2/3 of the total coating thickness, deposited from a standard electrolyte, contains virtually no sulfur. The second layer of nickel is deposited from a bright nickel plating electrolyte; sulfur contained in organic brighteners is part of the nickel coating, while the electrode potential of the second shiny layer shifts by 60-80 mV towards electronegative values ​​relative to the first layer. Thus, the shiny nickel layer becomes the anode in the galvanic couple and protects the first layer from corrosion.

Three-layer nickel plating has the highest corrosion resistance. With this method, after deposition of the first layer of nickel from the same electrolyte as in double-layer nickel plating, a middle layer of nickel is deposited from the electrolyte, which contains a special sulfur-containing additive, ensuring the inclusion of a large amount of sulfur (0.15-0.20%) in composition of the nickel intermediate layer. A third top coat of electrolyte is then applied to produce a shiny finish. At the same time, the intermediate layer, acquiring the most electronegative potential, protects the nickel layers in contact with it from corrosion.

In the automotive industry, two-layer nickel plating of the sil-nickel type is used. The first layer of nickel is applied from a bright nickel plating electrolyte. The parts are then transferred to a second electrolyte, where sil-nickel is deposited. Non-conducting highly dispersed kaolin powder is added to the composition of this electrolyte in an amount of 0.3-2.0 g/l. Temperature 50-60°C, current density 3-4 A/dm2. The process is carried out without continuous filtration. To provide uniform distribution kaolin particles throughout the entire volume of the electrolyte, intensive air mixing is used. The sil-nickel layer increases the wear resistance of the coating and has high corrosion resistance.

Sil-nickel is used as last layer before chrome in a protective and decorative coating. Due to the high dispersion of inert particles, a thin layer of sil-nickel (1-2 microns) does not change decorative look shiny nickel-plated surface, and with subsequent chrome plating allows you to obtain microporous chromium, which increases the corrosion resistance of the coating.

Removal of defective nickel coatings is carried out by anodic dissolution of nickel in an electrolyte consisting of sulfuric acid diluted to a density of 1.5-1.6.103 kg/m 3. Temperature 15-25°C, anode current density 2-5 A/dm 2.

Along with electrolytic nickel plating, the chemical nickel plating process is widely used, based on the reduction of nickel from aqueous solutions using a chemical reducing agent. Sodium hypophosphite is used as a reducing agent.
Electroless nickel plating is used to coat parts of any configuration with nickel. Chemically reduced nickel has high corrosion resistance, great hardness and wear resistance, which can be significantly increased by heat treatment (after 10-15 minutes of heating at a temperature of 400°C, the hardness of chemically deposited nickel increases to 8000 MPa). At the same time, the adhesion strength also increases. Nickel coatings reduced with hypophosphite contain up to 15% phosphorus. The reduction of nickel by hypophosphite proceeds according to the reaction NiCl 2 + NaH 2 PO 2 + H 2 O → NaH 2 PO 3 + 2HCl + Ni.

At the same time, hydrolysis of sodium hypophosphite occurs. Degree beneficial use HPP is taken about 40%.

The reduction of nickel from its salts by hypophosphite occurs spontaneously only on iron group metals that catalyze this process. To coat other catalytically inactive metals (for example, copper, brass), it is necessary to contact these metals in solution with aluminum or other metals that are more electronegative than nickel. For this purpose, surface activation is used by treatment in a solution of palladium chloride (0.1-0.5 g/l) for 10-60 s. On some metals, such as lead, tin, zinc, cadmium, a nickel coating does not form even when using the contact and activation method.
Chemical deposition of nickel is possible from both alkaline and acidic solutions. Alkaline solutions are characterized by high stability and ease of adjustment. Composition of the solution and nickel plating mode:

Nickel chloride - 20-30 g/l
Sodium hypophosphite - 15-25 g/l
Sodium citrate - 30-50 g/l
Ammonium chloride 30-40 g/l
Ammonia aqueous, 25% - 70-100 ml/l
pH = 8-9
Temperature = 80-90°C

Coatings obtained in acidic solutions are characterized by less porosity than those obtained from alkaline solutions (at a thickness above 12 microns, coatings are practically non-porous). The following composition (g/l) and nickel plating mode are recommended for acidic solutions of chemical nickel plating:

Nickel sulfate - 20-30 g/l
Sodium acetate - 10-20 g/l
Sodium hypophosphite - 20-25 g/l
Thiourea 0.03 g/l
Acetic acid (glacial) - 6-10 ml/l
pH = 4.3-5.0
Temperature = 85-95°C
Deposition rate = 10-15 µm/h

Electroless nickel plating is carried out in glass, porcelain or iron enamel baths. Carbon steel is used as the suspension material.
IN Lately a nickel-boron alloy is chemically coated using boron-containing compounds as a reducing agent - sodium borohydride and dimethyl borate, which have a higher reducing ability compared to hypophosphite.
The resulting nickel-boron alloy coatings have high wear resistance and hardness.

To estimate the cost of work, please send a request by email[email protected]
It is advisable to attach a drawing or sketch of the products to your request, as well as indicate the number of parts.

In the price section it is indicated cost of nickel plating of products

Hi all! The purpose of the article is to show the nickel plating process from all possible sides. Namely, how to achieve high quality coating without spending 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 the food industry to prevent iron contamination of foods.
• 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 get different kinds 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, chemical composition, which we will make, is very poisonous. 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;
• In good hardware store you can find nickel-plated welding electrodes;
• 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. Largest quantity Nickel contains strings that consist of a steel core, which in the future can “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 the charger for mobile phone, 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 copper wires without insulation.
• Twist copper wires without insulation together, forming 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 bare 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 buy various salts nickel, but there is no spirit of the inventor in this. 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, a very small amount of chlorine gas (from the salt) will also form on the positive terminal, but if you don't put significant amount salt or use low voltage, then the concentration of chlorine that dissolves in water will not exceed 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 at room temperature and does not tarnish. 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.

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.

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.

Nickel plating

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 exceeding operating temperature. (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 training their surfaces.

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 - 20 s.

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.

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 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 up to 2 dm2 in area.

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 succinic acid - 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 GOST standards, a single-layer nickel coating per 1 cm2 has several dozen through pores (to the base metal). Naturally, on outdoors steel part, plated with nickel, will quickly become covered with a “rash” of rust.

During operation, materials are subject to physical wear. Numerous methods of protection are used to restore the properties of the metal. One of the most effective methods protection is nickel plating of materials.

To apply nickel at home, chemical and electrolytic nickel plating methods are used.

What is nickel plating?

Nickel plating is the process of applying a thin nickel coating to the surface of a material. The nickel layer is taken to be 1–50 µm.

The nickel layer is used to increase the anti-corrosion and wear-resistant properties of the materials. Quite often, such a coating has a protective and decorative value.

Nickel plating is used for processing steel and non-ferrous alloys. A thin layer of nickel is used to protect products made from manganese, titanium, tungsten, molybdenum and alloys based on them.

Methods for applying nickel protective coatings to ceramics, plastic, porcelain, glass and other non-metallic surfaces have been developed and successfully implemented.

Types of nickel plating

Nickel plating in simple home conditions is carried out in two ways:

• electrolytic;
• chemical

The choice of method depends on the structure and shape of the material.

The electrolytic method uses substances that partially or completely consist of ions and have ionic conductivity. Nickel coating is applied due to the electrochemical properties of these substances. The most widely used electrolytes are sodium and chromium sulfate.

Depending on the degree of reflection of the coating, nickel plating is distinguished:

Functions of electrolytic nickel plating

• matte;
• shiny.

To apply a matte finish, electrolytes without additives are used. Products with a matte finish do not have a metallic sheen.

Bright nickel plating is obtained by adding special brightening agents based on chloramine, propargyl alcohol, benzosulfamide and other oxidizing agents to the electrolyte.

The best protection of nickel coating is achieved with minimal porosity of the protective layer. For this purpose, it is copper-plated or a multilayer structure of the material is used.

For your information. With the same thickness, multilayer coatings are several times more reliable than single-layer materials.

The most common examples of multilayer materials are copper-nickel-chromium coatings.

The main disadvantages of electrolytic nickel plating are:

• high degree of porosity;
• uneven deposition of nickel;
• difficulty in processing surfaces with complex shapes.

The method is based on the property of nickel ions to be reduced in a liquid medium. For this purpose, sodium hypophosphite or other chemical reagents are used. The chemical method allows you to process products with complex surface shapes.

The disadvantage of this method is the relative high cost of dry reagents used to prepare aqueous chemical solutions.

Carrying out electrolytic nickel plating at home

Electrolytic (galvanic) nickel plating of parts is carried out in two ways:

• immersing parts in electrolyte;
• without immersing parts in electrolyte.

The first method is used when processing small-sized parts. The second method is used when processing large and heavy objects.

Before nickel plating, the metal is copper-plated.

Electrolyte immersion method

In the first method, the surface of the product is ground sandpaper for removing oxide film. The sample is then washed in warm water. After this, it is treated with a soda solution and washed again in warm, clean water.

Then two thin copper plates are placed in a glass or porcelain dish. The plates act as anodes. They are placed in a vertical position, parallel to each other.

The product is placed between these two plates. To do this, the sample is suspended using a wire. The wire is attached to the plates at both ends.

An aqueous electrolyte solution with the following composition is added to the dishes:

• distilled water;
• 20% copper sulfate;
• 2% sulfuric acid.

The copper plates are connected to a power source. The voltage value is determined at the rate of 15–20 mA per 1 cm2 of the surface of the material.

For your information. Nickel electrolyte is sensitive to changes in acidity. To maintain the acidity level, buffer compounds based on boric acid are used.

In an electrolyte solution, copper chloride dissociates (breaks up) into its constituent components. The ions are displaced towards the cathode and become neutral atoms. Chlorine ions are oxidized at the anode.

When current is passed through an electrolyte, copper ions pass into solution. From solution, copper settles on the cathode in the form of neutral atoms. Impurities remain at the bottom of the pan. The purity of the resulting copper is almost 100%.

After 30 minutes, a thin layer of copper will form on the part. Impact electric current causes an increase in the thickness of the copper layer. The greater the thickness of the layer, the fewer pores remain on the treated surface.

Method without immersing parts in electrolyte

Galvanic nickel plating of large parts is carried out without immersing them in an electrolyte. To do this, use a brush made of loose copper wires. A stranded copper cable stripped of insulation is often used as a brush.

By increasing the deposited copper layer, the porosity of the sample surface is eliminated.

The nickel deposition process is carried out similarly to the surface copper plating process. To do this, add electrolyte to the container. The electrolyte contains the following chemical reagents, g/l:

• sodium sulfate solution – 310;
• nickel chloride solution – 65;
• orthoboric acid – 45;
• 1,4-butanediol – 0.15;
• ortho-sulfobenzimide (saccharin) – 2.0;
• kaolin (lime) – 1.0.

Thin nickel plates are dipped into the electrolyte. They play the role of anodes. The product is placed between them. The ends of the plates are connected to the terminal of the power source with a positive charge. The body of the part is connected to the negative pole.

A rheostat is used to regulate the current value. The amount of supplied electric current is monitored using a milliammeter. The magnitude of the supplied current should not exceed 6 V. Nickel deposition is carried out at a temperature of about 50°C and an electric current density of 4–5 A/dm2. The duration of the process is 3 minutes.

For your information. Nickel coating without a substrate has rather weak adhesion to the surface. In order to increase adhesion, heat treatment of the product is used at a temperature of 450 degrees.

The final stage of part processing

The treated part is washed under a stream of clean warm water and dried.

The nickel-plated finish has a matte finish. The part is polished to add shine.

Nickel coatings with defects are removed by anodic dissolution in an electrolyte. To do this, sulfuric acid is included in the electrolyte. The chemical density of the acid is taken to be 1.2-2.8 kg/m3. The process of removing the nickel layer is carried out at a temperature of 20-25 ° C and an anodic electric current density of 5 A/dm2.

Carrying out electroless nickel plating at home

Chemical nickel plating at home is carried out using working solutions. Depending on the amount of dry reagents, the rate of increase in the nickel layer is 80 µm/h or more.

The working solution contains the following reagents, g/l:

• nickel sulfate (nickel sulfate powder) – 20;
• galena (lead sulfide powder) – 20;
• sodium acetate – 15;
• sodium hypophosphite solution – 25.

The operating temperature of the chemical solution is 90°C. When the lead reagent is removed, the reaction rate decreases to 50 µm/h or less.

When the operating temperature is reached, the workpiece is lowered into the container with the solution. Before nickel plating, the coating is cleaned and degreased.

The product is kept in the working solution for 1 hour. As it evaporates, add distilled water.

Upon completion of the process, the part is removed and washed in warm water. After rinsing, the product is thoroughly dried. If necessary, polish thoroughly.

Increased service life of nickel plating

Nickel plating can be subject to continuous surface corrosion. The corrosion process appears only in the initial period. As the temperature of the working solution increases, surface corrosion penetrates deep into the material. Then this process slows down and stops completely.

To increase the service life of the nickel coating, copper plating technology is used. Copper plating can also eliminate minor surface defects. The application of copper as a substrate ensures the reliability and durability of nickel protection.

The porosity of the copper coating causes the destruction of the protective layer and reduces the service life of the finished product. The substrate metal undergoes corrosion, followed by peeling of the protective layer.

Most often, products with a single layer are exposed to corrosion processes. protective coating. Multilayer parts are exposed to harmful factors less.

To protect products from damage, a number of additional measures are taken. Special additives are used to close the pores.

For your information. To prevent loss of hardness, nickel plating of steel is carried out at a temperature of 250-300ºС.

Additional processing of parts to extend service life

Nickel plating at home is carried out using the following methods:

• The dry magnesium oxide reagent is mixed with water until it turns into a paste. The resulting mass is carefully processed and the part is immersed for several minutes in 50% hydrochloric or sulfuric acid.
• The working surface is wiped with penetrating lubricant. The product is then immersed in purified fish oil. Excess fat is removed after 24 hours using gasoline or other solvents.
• Larger parts are treated with fish oil in two passes. The interval between treatments should be at least 12 hours. After two days, excess slave fat is removed.

The use of nickel alloys with other metals can improve physicochemical characteristics nickel

Aluminum helps increase the electrical resistance and corrosion resistance of nickel.

Tungsten, molybdenum and titanium increase its heat resistance.

The addition of chromium increases the resistance of the nickel coating in oxidizing and reducing solutions.

Copper increases nickel's resistance to various acids.