Home electroforming. Electroplating at home: technological process and necessary equipment

After publishing my previous idea - Serious electroplating business - I received so many questions about the technological process that I decided to combine my answers into a separate idea.

Technological equipment for electroplating

1. sulfuric acid bath
2. cold water bath
3. hot water bath
4. ironing bath
5. cold water bath
6. work table on wheels
7. baskets and bottles with acids
8. welding transformer
9. ballast rheostats.

Technological cycle

Includes the following operations:
1. Preliminary preparation.
2. Sulfuric acid passivation.
3. Rinse in cold water.
3. Rinsing in hot water.
4. Ironing.
5. Rinse in cold water.
6. Further processing.

Preliminary preparation

Consists of the following. The received shaft is wiped with a rag to remove any remaining oil, and dirt is removed from the keyways. Then the dimensions of the neck are taken in places of maximum production and the undeveloped dimensions. This is necessary to establish the thickness of the required coating and determine the ironing time. If the shaft is damaged (large ellipse, cone), then to restore the correct geometry it is subjected to grinding, but no more than 0.5 percent of the total diameter of the neck is removed. This way the thickness of the required coating is determined.

N(mm) = Nv(working) + 3Nm.sh.(minimum grinding of the machine)

the value 3Nm.sh can be set even more

To determine operating currents, it is necessary to know the cathode (covered) area. To do this, measure the diameter of the neck and its width and then according to the formula

S = π D A,

where A is the width of the neck.

The area is calculated in square decimeters.

Thus, having found out the area and multiplied it by the recommended current density (A\sq.dm), we will know the value of the total required current.

The time required for ironing is found using the formula:

T(hours)=7400*N / Ic*n,

Where:
Ic = I cathode - Ianodic A/dm.
n is the current output of iron, determined practically, but you can use the empirical formula: n = 47(Ic)0.2

Sulfuric acid passivation

After all calculations are completed, we begin the process.

Rubber plugs are plugged into the oil channels.

In order to prepare the shaft surface for ironing, the sulfuric acid passivation method is used. Various modes are used ( alternating current, asymmetric current), but the fastest and most productive is the etching mode at the anode, which allows, simultaneously with passivation, to clean the surface from oil and varnish films.

To do this, the shaft is placed in a sulfuric acid 20-30% solution and connected to the + bus; the cathode is made of sheet lead and its area must exceed the area of ​​the part at least 10 times. Then a current with a density of up to 50A/sq.dm is switched on. Time – 1 min. The current is constant (rectified).

During this time, the surface of the part acquires an even matte dark gray shade. This completes the passivation operation.

Hot and cold water rinsing

Ironing

If you need to restore a specific area, and not the entire part, masking is used - the area that is not subject to ironing is painted over with nitro varnish or nitro paint. Since nitro coatings are very porous, painting should be done in at least two layers, with intermediate drying.

The ironing process is carried out at a temperature of 18-25°C. Anodes made of steel St.3…..St.20. Alloy steels are not used as anodes, because Chromium ions complicate the process and reduce the quality of the coating.

Actually, the ironing process itself is divided into several stages. The first stages serve to create a uniform primary layer, firmly bonded to the base. The last stage serves to build up the working layer with the required hardness.

1. Cathode current - 20 A/sq.dm, anode current - 15.5 A/sq.dm. Time - 15 sec. Coating hardness 180 kgf/sq.mm.

2. Cathode current - 20 A/sq.dm, anode current - 10 A/sq.dm. Time - 60 sec. Coating hardness 270 kgf/sq.mm.

3. Cathode current - 20 A/sq.dm, anode current - 5 A/sq.dm. Time - 60 sec. Coating hardness 400 kgf/sq.mm.

4. Cathode current - 20 A/sq.dm, anode current - 3.5 A/sq.dm. Time - 30 sec. Coating hardness 540 kgf/sq.mm.

5. Cathode current - 30 A/sq.dm, anode current - 3.5 A/sq.dm. Time - 30 sec. Coating hardness 630 kgf/sq.mm.

This is where the “tightening” process ends and then the working layer is built up to the specified dimensions.

6. Cathode current - 30 A/sq.dm, anode current - 3 A/sq.dm. Time is estimated. Coating hardness 630 kgf/sq.mm.

Rinse water from baths 2 and 5 is used to top up the ironing bath. During operation, sludge is released from the anode, which must be removed after settling.

And one more detail. Before starting ironing, you need to “work out” the electrolyte. To do this, hang an unnecessary piece of metal from the cathode and turn on the cathode current of no more than 10 A for one or two hours. This is necessary to clean the solution from impurities and to remove 3-valent iron. Iron with valency 2 is deposited.

If you had a break in work lasting more than a day, the electrolyte must also be worked out.

If you were unable to obtain salt of pure grade or analytical grade, and you are using a gardening chemical, then the process of working out the electrolyte should be carried out with the minimum cathode current; anode current is not used. The current value is set “on the verge” of the beginning of gas formation at the cathode.

It goes without saying that this process will take much longer than when working with pure reagents.

Electrolyte composition:
ferric chloride - 400-440 g/l
sulfuric acid - 0.8-1 ml\l
potassium iodide - 5-10 g/l
hydrochloric acid - up to pH = 1–1.2

Acidity is determined by litmus or indicator paper.

The hardness of the coating is determined by Rockwell or Brinell.

To begin with, you should not chase hardness and performance, try working in modes 1 and 2, try restoring some part that can then be processed with a file, cutter or drill. When you start to succeed, you will gradually move on to complex-profile parts and increasing hardness.

I am far from thinking that galvanization with asymmetric current is a panacea for all ills and a solution to all problems. It's just a tool. And just like any tool, it cannot be universal for all occasions. Traditional electroplating is no worse, it’s just different.

The purpose of the publication was to draw attention to the fact that thanks to changes in prices for electricity and metal in the domestic and foreign markets, it became possible to receive good material benefits from this process.

If in Soviet times light cost 2 kopecks, and a kg of iron was 12-16 kopecks, but today the difference in price is higher: light is 2.86 tenge, and metal is more than 50 tenge per kg. If previously the cost of such repairs did not exceed 60% of the original cost, today this figure is much lower. And this is only about hardware. I'm not even talking about the prices for “food grade” tin. If anyone is interested, check out the stock prices. Each can of condensed milk or stew contains from 0.75 g to 2 g. And the process of removing this coating by electroplating takes no more than 4-5 minutes. Work out - I don’t want to. Under this ball, you can pretend to be a fighter for the environment (while remaining at heart an ideological fighter for banknotes) and if you don’t shy away from taxes, then try to reduce them. I don’t think anyone needs to be told about the deposits of this raw material and the labor reserves located there, and sometimes living right on these mines. In large cities, these landfills are mostly electrified. In any case, there is light in the director's trailer. Nobody bothers.....except the crows. :-))))

In 1840, a Russian physicist of German origin, Moritz Hermann, who, after moving to Russian Empire changed his first and last name to Boris Jacobi, writes a work under long name: “A method of producing, according to given samples, copper products from copper solutions using electricity or Electroplating for the applied arts.” From this scientific work The history of electroplating begins not only in Russia, but also in the world.

In his research, Jacobi relied on the earlier work of the Italian physicist Luigi Galvani, and therefore called the process galvanoplasty, and the container in which this miracle occurs - a galvanic bath.

Currently, electroplating is a branch of electrochemistry and studies the deposition of electrolytes on the surface of metals. In turn, galvanization will be divided into two large subsections:

• Electroplating: electrochemical copying method. With its help they apply enough thick layer metal and, as a result, receive an exact copy of the copied object. In particular, this method is used to produce vinyl records and laser compact discs.
• Electroplating: electrochemical technology of coating a substrate with a layer of metal in order to obtain a stronger or more decorative layer. Often these two tasks are combined.

Through the process of electroplating, it is possible to coat with a layer of metal and chrome-plate almost any surface: metal, plastic, wood, leather. Chrome-plated boots or nickel-plated boots are a very real thing, but not entirely practical. Coating one metal with another in order to increase anti-corrosion, strength and aesthetic characteristics is much more in demand. Processes such as chrome plating, nickel plating, copper plating, and galvanizing have long become common practice in large-scale industrial production.

DIY chemical metallization at home. Electroplating at home is a very real thing, of course, if certain requirements are met. Of all the types of home electroplating, chrome plating is perhaps the most complex look electroplating for two reasons:

• Technical complexity of the process.
• Extreme danger of chemical components to health.

First technical difficulty

The difficulty of chrome plating is that very stringent requirements are imposed on the operating mode galvanic bath. The slightest deviations from the required current density, temperature and electrolyte concentration lead to a sharp change in the quality of the chrome coating, even to the point of rejection.

The ability of chromium to change greatly in qualitatively, depending on the electrolyte temperature and current strength, is actively used in production to produce chrome coatings with varying degrees of gloss, color and strength.

• At an electrolyte temperature of 30−60 degrees, the surface finished product will be brilliant.
• Above 60 degrees - the chrome coating will have a milky tint.
• Below 30 degrees – the surface is matte.

Chromium changes color depending on the concentration of the electrolyte composition, and along with the color, the strength characteristics also change. The color changes from the usual light, to dark blue, agate, blue and, finally, to almost black. As the color changes, so does the strength of the chrome coating. The softest chrome has regular light color, to obtain it you need room temperature and current strength is about 5 A/sq.dm. The most durable chrome coating is black chrome. But to obtain black chrome, a current of 100 A/sq.dm is required, which under conditions home production it is technically impossible to do.

Second technical difficulty

The second difficulty is that chromium cannot be directly bonded to steel, aluminum, cast iron or iron. Therefore, the nickel plating process is always carried out before chrome plating. Often, in order to obtain a better result, several successive layers are applied: nickel, copper, nickel again, and only finally a layer of chromium is applied.

It should be borne in mind that the chrome coating itself has rather contradictory characteristics. On the one hand, chromium has a high mechanical strength(much higher than nickel), chemical inertness and very bright luster. But at the same time, it is very fragile and has a porous structure. Therefore, a nickel substrate for the chromium layer is necessary even if chrome plating is carried out on the surface of a metal with which chromium has good adhesion, for example, copper or brass.

Thus, the process of chrome plating at home automatically involves at least two sequential technological processes: nickel plating and chrome plating.

Health Hazard

The main component of the electrolyte for chrome plating is chromium oxide (CrO3) or, as it is also called, chromic anhydride. It just so happens that chromic anhydride is the strongest poison and at the same time one of the most powerful carcinogens. Lethal dose for humans, when taken orally, it is approximately 4-6 grams, depending on the individual’s weight. When hitting open areas On the skin of pure chromium oxide or its solutions, chemical burns occur, which then develop into dermatitis and eczema, followed by degeneration into skin cancer.

When chromium oxide combines with substances of an organic nature, such as technical solvents, gasoline, kerosene, an instant fire and explosion occurs.

It is clear that such a “wonderful” chemical substance cannot simply be bought in a chemical store. reagents. The circulation of chromic anhydride is strictly regulated by the state and sales are permitted only legal entities having a license for the relevant type of activity.

Necessary equipment

Only a potential suicide can carry out chrome plating in the kitchen of a residential apartment. In order to begin the process of chrome plating a headlight, you must have a special room for this, as far away as possible from residential buildings. A spacious workshop or garage is best suited for these purposes. It is necessary to have a good forced ventilation. All containers with gasoline, paints, varnishes and other solvents must first be removed from the premises. It is mandatory to purchase a good fire extinguisher and consider an option for an emergency exit from the premises in the event of an emergency.

For chrome plating you must have:

• Galvanic bath. Either glass or durable plastic that can withstand temperatures up to 100 degrees.
• Rectifier. Constant current source with the ability to regulate the output voltage. Parameters - 12V/50A. If we are talking about small parts, then you can use Charger for a car battery.
• Heater. Must withstand long-term exposure to an aggressive acidic environment. For example, a ceramic heating element. An ordinary heating element will not work.
• Thermometer. With divisions from 0 to 100 degrees. Optimal temperature for the process is 45−55 degrees.

It must be borne in mind that to optimize the process it is necessary to equip at least two such installations, one for chrome plating and the second for nickel plating. Otherwise, you will have to constantly change reagents in one container, which is extremely inconvenient and costly.

Three parts of the galvanic process

Electroplating at home, chrome plating is an electroplating process. Therefore, to carry it out three components are required: cathode, anode and electrolytic environment in which the transfer of charged metal particles will occur.

• Cathode. A plate of pure lead or an alloy of lead and tin. It must be remembered that the cathode area must be more area anode. The cathode is connected to the positive output of the rectifier.
• Anode. This is the chrome-plated part itself. It should hang in the electrolyte medium so as not to touch the walls and bottom of the container. In addition, the anode must never touch the cathode.
• Electrolyte. Chromium plating requires particularly careful preparation of the electrolyte.

Electrolyte preparation

Electrolytic fluid kit for chrome plating includes the following components:

• Chromic anhydride: 250 g/l.
• Sulfuric acid: 2−3 g/l. Chemically pure, concentrated. Technical sulfuric acid is not suitable.
• Distilled water.

The water is heated to a temperature of 60−80 degrees. After this, the anhydride dissolves in it. The solution is cooled slightly and then added to it in a thin stream required amount sulfuric acid.

Preparing the surface of a chrome-plated product

Consists of three stages:

• Mechanical cleaning, grinding and polishing.
• Degreasing.
• Nickel plating.

The peculiarity of chrome plating is that, on the contrary, it emphasizes all existing irregularities, chips and cracks on the surface of the product. Therefore, traces must first be removed from the surface of the chrome-plated part. old paint, rust, chips, cracks and other defects. Preparation of the chrome surface with consists of the following steps:

• Sandblasting.
• Polishing with fine sandpaper.
• Grinding soft materials and polishing paste.

Do not use gasoline or White Spirit for degreasing. Otherwise there will be problems with the quality of chrome plating. The best option — prepare a special solution:

• Caustic soda: 150 g/l;
• Soda ash: 50 g/l;
• Silicate glue: 5 g/l.

The solution is heated to 90 degrees. After that, the part is lowered into it and kept for 20-40 minutes, depending on the area and surface relief of the part.

Nickel plating is the last stage preparing the part for chrome plating. The nickel plating process is carried out in a special galvanic bath. The cathode in this case is metallic nickel, and the electrolyte is a solution of sulfuric acid and nickel salts.

Chrome plating stages

Direct chrome plating consists of a number of successive stages:

• The process begins by raising the temperature of the electrolyte in the bath to 50-54 degrees.
• A chrome-plated part is placed with the cathode output first connected to it.
• After this, wait for some time without applying voltage to the system. During this time, the temperature of the part and the electrolyte should equalize.
• After applying voltage, the workpiece is in the solution for at least 20 minutes. In some cases, chrome plating can last 2-3 hours. Everything is decided on an individual basis depending on the size of the part and the required final characteristics of the chrome coating.
• After the process is completed, the part is removed from the solution, washed and placed in a drying cabinet for 2-3 hours.

There are a lot of video tutorials on galvanizing on the Internet, in particular, on chrome plating of metals. Therefore, all the details of this process can be found there.

Galvanization is also a section applied science"Electrochemistry", which studies the processes that occur during the deposition of metal cations on a cathode placed in an electrolytic solution, and technological process. Electroplating at home or performed in production allows you to apply it to the surface of the workpiece. thin layer metal, which can act as a protective or decorative coating.

Methods for implementing such a technological process, which is quite complex, have already been well developed, so today it is actively used not only by manufacturing enterprises, but also by many home craftsmen.

Process Features

The coating formed on the workpiece using galvanization can be applied for technological purposes or perform decorative, protective, or both functions at once. For decorative purposes, a thin layer of gold or silver is created, and to ensure reliable protection the surface of the workpiece from corrosion, perform galvanizing or galvanic copper plating.

It is not difficult to do electroplating even at home. This procedure is performed as follows.

• Two anodes are lowered into a dielectric container with electrolyte, connected to the positive contact of the electric current source. The material used to manufacture such anodes must be metal, the layer from which must be formed.
• The workpiece itself, connected to the negative terminal of the electric current source and thus acting as a cathode, is placed in the electrolyte between the anodes.
• Galvanization, that is, the process of transferring metal molecules from the electrolyte to the cathode product, begins to occur at the moment when the resulting electrical network is closed.

As a result, a thin and uniform layer of metal is formed on the treated surface, which was originally contained in the chemical composition of the electrolyte.

Necessary equipment

Do-it-yourself electroplating can be done with high quality using even the simplest equipment that many craftsmen have in their arsenal. First of all, you should select a direct current source, which must be equipped with an output voltage regulator. The presence of such a regulator is necessary in order to be able to smoothly and widely change the power of your homemade device for electroplating.

As a power source at home, it is very convenient to use an electric current rectifier, which you can assemble yourself (or purchase a serial model). Many craftsmen who perform galvanic coating at home use commercial welding machines as a power source.

A do-it-yourself galvanic bath can also be made without any problems. Any container made of glass or plastic can be used as such a bath, but it must be taken into account that such a container for electroplating must contain both the workpiece and the required amount of electrolyte. It is also very important that the bath is strong enough and can withstand high temperatures, the value of which can reach up to 80°.

Anodes used for electroplating at home perform several important functions:

• add to electrolyte electricity and ensure uniform distribution of the latter over the treated surface;
• compensate for the loss of metal applied to the product, consumed from the chemical composition of the electrolyte;
• promote the occurrence of certain oxidative processes.

When choosing anodes for your galvanic apparatus, you should observe one thing: important rule: their area must be larger than the area of ​​the surface being treated.

Electroplating at home cannot be done without using heating device, with the help of which the electrolyte is brought to the required operating temperature. It is very convenient when the intensity of heating provided by such a device can be adjusted. If we rely on the experience of home craftsmen who already have experience in applying galvanic coatings at home, we can recommend using a small electric stove or regular iron with adjustment of the degree of heating of the sole.

What is needed to prepare the electrolyte?

To safely store at home the chemical reagents from which the electrolyte for electroplating will be prepared, as well as the finished solution itself, you will need glass containers with ground-in lids. The amount of chemical reagents from which the electrolytic solution is prepared must be measured with an accuracy of one gram. To solve this problem at home, even inexpensive electronic scales, which can be purchased at any hardware store, are suitable.

If you decide to apply electroplating to various products at home, you will probably encounter the problem of purchasing chemical reagents from which the electrolytic solution is prepared. The fact is that organizations that produce and sell such chemicals can only sell them to those who have the appropriate permits. It is problematic to purchase such chemical reagents for a private person or even an organization that does not have such documents.

How to properly prepare the product for the procedure

After you have made your electroplating apparatus, found all the necessary equipment and chemical components, you can begin such an important process as preparing the product that will be subjected to electroplating. The importance of such a process is very difficult to overestimate, since the quality of its implementation largely determines what characteristics the finished coating will have.

In most cases, preparing a product for electroplating is not limited to just cleaning its surface from dirt and degreasing it. Subsequent grinding is also carried out using sandpaper and special pastes.

Electroplating highlights all surface imperfections, so the workpiece must be ideally prepared, that is, all chips, scratches and cavities must be eliminated

In order to degrease the surface to be treated before galvanizing, you can use pure organic solvents or prepare a special solution for this purpose. In particular, to effectively degrease steel or cast iron at home, solutions are prepared that contain caustic soda, liquid glass, sodium carbonate and sodium phosphate. Degreasing of products made from such metals is carried out in a solution heated to 90°. Non-ferrous metals can be effectively degreased with solutions containing laundry soap and sodium phosphate.

To obtain high-quality galvanic coating both at home and in production conditions, it is also necessary to remove the oxide film from the surface being treated, for which special pickling solutions with sulfuric or hydrochloric acid are used.

Safety requirements

Any galvanic operation (zinc plating, chrome plating, nickel plating, copper plating, etc.) is a dangerous technological process, therefore, when performing it at home, it is necessary to strictly follow safety requirements. What makes electroplating dangerous are both toxic chemicals and the high temperature of the electrolyte, as well as the risks associated with any electrochemical processes.

To carry out electroplating at home, it is better to allocate a non-residential premises, which can be a garage or a workshop. It must have high-quality ventilation. All electrical equipment, which you will use to do electroplating, must be grounded.

Personal safety is the most important rule that should be strictly adhered to when performing electroplating at home. Measures that can ensure such security include:

• use of a respirator to protect the respiratory tract;
• protect your hands with soft and durable rubber gloves;
• use of an oilcloth apron and shoes when working that can protect the skin of your feet from burns;
• protection of the organs of vision with the help of special glasses.

In addition, during the galvanization procedure you should not eat or drink anything, so as not to accidentally ingest harmful fumes.

To be prepared for any surprises that may arise during such an operation, it is better to first read specialized literature or even watch a training video on this topic.

Nickel plating

Coating metal with a layer of nickel at home can be done as finishing or before chrome plating. This process is called “galvanostegy”, since a layer of nickel applied to the surface of the product increases its resistance to negative factors. external environment. In addition to its high protective properties, the nickel layer is also distinguished by its decorative appeal.

The electrolyte temperature when performing nickel plating does not exceed 25°, and the current density is within 1.2 A/dm 2. The electrolyte, the acidity of which should be within 4–5 pH, is an aqueous solution containing such chemical elements, such as nickel sulfate, magnesium, sodium, table salt, boric acid.

After the electroplating process is completed, the product is removed from the electrolytic solution, washed in water, thoroughly dried and polished.

Chrome plating

Galvanic chrome plating at home or at manufacturing plant allows you to give the surface layer of the processed product higher hardness, resistance to corrosion, and also decorativeness. Since chrome plating is characterized by fairly high porosity, it is performed after galvanic application of copper to the workpiece (or nickel plating). To perform this technological operation, anodes are used that are made of an alloy of lead, tin and antimony.

The final result of chrome plating, which is quite difficult to do at home, since it requires the use of high-density currents - up to 100 A/dm 2, is influenced by various factors. The most significant of them include:

• the temperature of the electrolyte used - the shade of the formed coating depends on this parameter, which can be matte (temperature below 35°), shiny (35–55°) and milky (above 55°);
• chemical composition electrolyte, which affects the protective properties of the coating being formed, as well as its color, which can be dark blue, blue, agate.

The final stage of chrome plating after removing the part from the electrolytic solution is washing the treated surface with water, followed by neutralization in the solution baking soda, another washing, drying and polishing using special pastes.

Copper plating

Copper plating using electroplating at home is necessary in order to create a conductive layer on the surface of the workpiece, which has a small value electrical resistance, and also in order to protect the part from negative impact external environment.

Applying a layer of copper to steel and cast iron products without first covering them with a layer of nickel is deadly, since this requires the use of cyanide electrolyte.

After preliminary nickel plating, the metal is coated with a layer of copper using a solution of copper sulfate, concentrated sulfuric acid and water at room temperature.

There are two types of galvanization - galvanostegy and galvanoplasty. In the first case, a permanent galvanic coating is obtained, which changes the characteristics of parts and objects. Depending on the goals pursued, the processed products acquire new properties: decorativeness, good reflectivity, resistance to mechanical stress and corrosion, wear resistance. Using electroplating, exact copies of samples are created at home or in production (the deposited layer of metal is separated from the matrix).

Galvanization technology: general information

Regardless of whether it is performed at home, the treatment is carried out in a container filled with a conductive solution.

The object is placed between two soluble or insoluble anodes and connected to the negative terminal. The anodes are connected to the positive contact. The optimal ratio of cathode/anode areas is 1:1.

The galvanization process starts when the electrical network– from this moment the transfer of metal ions to the negatively charged product (cathode) begins. As a result, a coating of the required thickness is formed on the object.

Selecting the type of coating

If the priority is solving technical problems (changing electrical conductivity and antifriction properties, increasing reflectivity, strength, corrosion resistance), then silver, nickel, and copper are used. Precious metals are usually used for decorative purposes: rhodium, gold, silver, palladium

This division is very arbitrary. With the help of silvering (gold plating) it is possible to obtain high-quality protective covering, resistant to aggressive environments. Copper plating is also used in the decoration of products (this coating is subject to additional oxide treatment).

Practice shows: it is possible to seriously increase the strength of processed workpieces by galvanizing their surface only in production. It is difficult to achieve the desired result in a home workshop, so the work of craftsmen is primarily aimed at increasing the attractiveness of the item.

Electroplating method

Do-it-yourself electroplating at home requires the use of special equipment. It doesn't have to be professional at all. Craftsmen find an affordable replacement.

When preparing a galvanic installation with your own hands, the master will have to find a plastic or glass bath of the required volume. A sufficiently durable, electrically insulating, acid-resistant container is required. The item being processed must fit into it and required quantity electrolyte and anodes.

The power source must have an output voltage and current regulator - this will allow the master to change the processing parameters during operation. Typically, the power source is a rectifier.

Important element home installation– soluble and insoluble anodes.

In order for the process to proceed correctly, the craftsmen follow optimal ratio areas of the part and anodes (1:1). Suspension devices provide support to the object and contribute to the correct distribution of current.

Electroplating process

Electroplating at home is carried out using reagents. Difficulties may arise at this stage - many chemicals are available only to those who have previously received permits.

Need to take care of proper storage components. Reagents, as well as finished electrolytes, are placed in glass or durable plastic containers with lids.

When preparing the composition, it is extremely important to measure all components with great accuracy - it is best to use electronic scales for this.

Preparatory process

The quality (uniformity, strength) of the finished coating directly depends on the correct preparation of the surface for galvanization. In many cases, removing contaminants and degreasing is not enough - sandblasting may be necessary. Sometimes sanding with special pastes or sandpaper is required.

At home, alcohol and other organic solvents are often used to remove greasy film and other contaminants from surfaces. Degreasing solutions may also be used.

When preparing for galvanization of steel and cast iron products, a solution containing soda ash, caustic, and silicate glue is used (per 1 liter - 50 g, 20 g and 5-15 g, respectively). The solution temperature is 70-90°C. To clean objects made of non-ferrous metals, use a solution of sodium hydrogen phosphate and household solid soap (10-20 g/1 l each). During the procedure, the temperature is 90°C.

Safety precautions

When carrying out galvanic operations, the master is obliged to observe safety precautions. The danger of this technological process lies in the use of toxic chemical components. Complicating the situation is heating the electrolyte to high temperatures. Harmful fumes affect the respiratory system, and there is a risk of chemical burns to the skin and mucous membranes.

Work must be carried out in non-residential premises equipped with good ventilation - in a workshop, outbuilding, garage. Grounding is required.

Eyes need to be protected with glasses. Hand gloves should be soft enough but durable. You will also need an oilcloth apron and rubber shoes.

You cannot eat or drink in the workplace - there is a high risk of sedimentation on food harmful substances which will lead to poisoning.

Before starting work, you should definitely study the special literature with accessible description features of the process.

Precious metals in electroplating

Galvanic gilding (silvering) is used to give the product decorative properties. When using the galvanic method, the craftsmen receive not just an ennobled precious metal item, but an exact copy of the original product. It can be either simple or complex. The metal layer applied to the workpiece is separated from the base.

The surface of objects made of ferrous metals is first copper plated before silvering. The temperature of the solution depends on the composition used. The anodes are made of silver with a purity of 999.

The electroplating process requires the use of ready-made electrolytes. The part is pre-cleaned and treated with galvanic nickel to improve adhesion. If the item is made of aluminum and its alloys, it is impossible to apply gold plating at home. The gold-plated object is thoroughly washed and then air dried.

Nickel in electroplating

A layer of nickel is applied to the workpiece before the gilding procedure. Nickel has good protective properties - it protects the surface of the workpiece from aggressive factors, withstands contact with different environments, and prevents oxidation and corrosion.

The nickel plating looks beautiful. The thickness of the layer varies - from 0.8 to 55 microns. When processing objects, sulfuric acid, hydrochloric acid or sulfamine electrolytes are used. Temperature, acidity, and current density depend on the composition of the solution.

Copper in electroplating

Copper plating:

• protects the surface of the workpiece from corrosion;
• creates a surface layer with low electrical resistance.
• It is worth considering that without prior nickel plating, cast iron surfaces can only be copper-plated in an alkaline electrolyte. This solution is used in production.

Electrochemical process - electrotype, that is, the deposition of a thick, massive layer of metal on the surface of any object, the shape of which they want to reproduce or copy, is quite common. For example, galvanoplasty is used in cases where metal part very complex shape and in the usual ways(by casting or machining) it is difficult or impossible to produce. This is how sculptures are sometimes reproduced from models (Apollo's chariot on the pediment of the Bolshoi Theater was made by electroplating).

This process is relatively simple and can be easily reproduced at home. First of all, an imprint is taken from the object or product being copied, that is, a mold is made from fusible metal, wax, plasticine or plaster. The object to be copied, rubbed with soap, is placed in a cardboard box and filled with Wood's low-melting alloy or other low-melting alloys.

After casting, the object is removed and the resulting mold is degreased and subjected to copper plating in an electrolytic bath. To prevent metal from being deposited on those sides of the mold where there is no imprint, they are coated with molten wax or paraffin using a brush. After copper plating, the low-melting metal is melted in boiling water to form a matrix. The matrix is ​​filled with plaster or lead, and the copy is ready. The following wax composition is used to make molds:

Wax.............20 century. h.
Paraffin.........3 c. h.
Graphite........1 c. h.

If the mold is made of dielectric (wax, plasticine, paraffin, gypsum), its surface
covered with an electrically conductive layer. The conductive layer can be applied by reducing certain metals (silver, copper, nickel) or mechanically - by rubbing flake graphite into the surface of the mold with a soft hair brush. Graphite is thoroughly ground in a porcelain mortar, sifted through a sieve or gauze and applied to the surface of the product with a soft brush or cotton swab. Graphite sticks better to plasticine. Forms made of plaster, wood, glass, plastic and papier-mâché are coated with a solution of wax in gasoline. Graphite powder is applied to the surface that has not had time to dry, and excess, non-adherent graphite is blown off.

The electroplated coating is easily separated from the graphite-coated mold. If the mold is made of metal, then on its surface it is necessary to create an electrically conductive film of oxide, sulfide or other insoluble salt, for example, on silver - silver chloride, on lead - lead sulfide, so that the mold is well separated from the coating. Copper, silver and lead surfaces are treated with a 1% solution of sodium sulfide, as a result of which insoluble sulfides are formed on them.

Deposition of metal on the surface of the mold. The prepared form is immersed in a galvanic bath, the circuit of which is energized so that the separating film does not dissolve. First, a “tightening” (coating) of a conductive layer of copper is carried out at a low current density in a solution of such
composition:

Copper sulfate ( copper sulfate)...150-200 g.
Sulfuric acid................................7-15 g
Ethyl alcohol...................30-50 ml
Water........................................1000 ml

The operating temperature of the electrolyte is 18–25° C, the current density is 1–2 A/dm2. Alcohol is necessary for
increasing surface wettability. After the entire surface is “covered” with a layer of copper, the mold is transferred to an electrolyte intended for electroplating. For galvanoplastic work (copper plating), the following composition is recommended:

Copper sulfate (copper sulfate)..... 340 v. h.
Sulfuric acid...................................2 c. h.
Water................................................. .1000 in. h.

Electrolyte temperature 25-28° C. Current density 5-8A/dm2.

Using the electroplating method, it is possible to metallize lace for decorative and artistic decoration. various items. The lace is stretched on a frame and impregnated with paraffin. They are then ironed between sheets of paper to remove excess paraffin. Next, an electrically conductive layer of fine graphite is applied, the excess of which is carefully blown off the lace. Having laid the conductors along the edge of the lace, they are attached to a plastic frame or a frame made of thick wire with vinyl chloride insulation, along with which the lace is immersed in an electrolyte.
Lace coated with copper is treated with a brass brush. They are soldered with tin-lead solder. Electroplating finishing of metallized lace involves applying a decorative layer of silver or gold or oxidation.