» Chemical staining of brass

Chemical staining of brass

Having bought, at one time, photo-etching from a Czech company Extratech for Tu-154M (on a scale of 1:144), I was amazed at the subtlety and delicacy of individual elements. Particularly pleased with the filigree imitation of riveting on the reverse buckets. The engine nozzles are of large-scale thickness. The rims on the chassis disks also look realistic.

The impression was strengthened by the new release for Il-62M , which has the same D-30KU engines.

At the same time, it became clear that now trying to prime and paint small details would ruin everything! Moreover, there are many methods of chemical processing of brass, allowing you to give it any color.

Most chemicals are always at hand - salt, soda, water. But it is still better to conduct experiments on the street or in a well-ventilated room, since toxic fumes and gases can be released. And no one canceled glasses and rubber gloves.

So, armed with long-forgotten chemistry textbooks and the Internet, let's get started!

P pre-bleached brass

Brass is an alloy of copper and zinc, sometimes with the addition of tin, nickel, lead, manganese, iron and other elements. And if copper has a pinkish tint, then brass is golden yellow.

Both brass and copper oxidize and darken in air. Therefore, before chemical treatment, it is imperative to remove oxides from the photo-etched surface.

RECIPE:

Alcohol or acetone
Citric acid (sold in grocery stores)
Salt

A teaspoon of citric acid and a teaspoon of table salt are added to a glass of hot water.

Photo-etching is degreased with alcohol or acetone and put into the solution for 5-10 minutes. At the end, it is washed with water and detergent.

Do not use metal utensils as a container, and remove the product with steel tweezers - a copper coating may remain.

Bleaching is accelerated by increasing the temperature of the solution or the concentration of citric acid.

Important! Do not overexpose the product in acid - the so-called "dezincification" of brass can begin - it becomes unnaturally pink-red.

The bleach solution is corrosive, so avoid getting it on your hands and clothes.

Burnishing of brass

So, let's try to simulate the color of the LPC blades of the Tu-154M engine.

For work we need:

1. 10% ammonia solution (sold in any pharmacy);

2. HOM - copper oxychloride (sold in garden stalls);

3. Glass jar.

Pour some ammonia into a jar and pour half a teaspoon of HOM. We stir. We add some water.

At first the solution has a cloudy turquoise color, then it becomes inky blue.

Having degreased with medical alcohol, we hang the brass piece on a thread and chat it in solution for about half a minute. Then rinse with clean water and dry.

The detail takes on a beautiful olive brown color, very similar to tape. The surface is perfectly flat.

It is important not to overexpose the part in the solution. It can become brittle and crumble.

Having created a dark base, we can now apply a thin layer of liquid-diluted metallic enamel paint of any color.

The whole operation from start to finish took no more than ten minutes.

Attention! Ammonia vapors are very harsh and poisonous. The process is best carried out on the street, in a respirator.

In conclusion, I want to answer the skeptics who they will say that working with photo-etching is long and difficult:

Nothing imitates metal like... metal itself.

I express my special gratitude to my colleague Sergey Utenko from Novosibirsk for valuable advice and comments.

Usually, both pure black and gray coloration is obtained by the formation of copper oxide or copper sulfide on the surface of the thing. But both of these colorings can also be achieved by deposition of sulfur compounds of other metals - lead, bismuth, mercury, etc. on the surface of the thing. Will the coloring be completely black or light black, i.e. gray, depends both on the composition that causes the color, and on the time of action of the latter.

Parts must be prepared, the surface must be perfectly clean, free of dirt and grease.

Chemical blackening

Hold the part for five minutes in a solution in which 0.9 g of sodium hydroxide and 0.3 g of ammonium persulfate (NH 4) 2 SO 8 per 100 ml of water (it is used in photography). Solution temperature 90-100 o C.

In a solution of potassium chloride, nickel sulfate NiSO 4 and copper sulfate CuSO 4 (respectively 4.5, 2 and 10.5 g per 100 ml of water) at the same temperature, copper and brass will acquire a pleasant chocolate hue.

The formation of black oxide of copper on the surface of things.

For the formation of black oxide of copper on the surface of things, the heated thing is immersed for several seconds in a solution of copper in excess of nitric acid and then held over a charcoal fire until its surface begins to turn black. To obtain a uniform and sufficiently dense black color, the operation is repeated several times, otherwise the color will not be completely black, but grayish. At the end of the staining, the thing is wiped with a cloth soaked in oil. Optical instruments are usually blackened in this way.

Blackening of brass and bronze.

For brass and bronze, the following solution can also be used: 2 parts of arsenic (not arsenic!) acid, 4 parts of hydrochloric acid, 1 part of sulfuric acid and 80 parts of water. Arsenic acid can be replaced with antimony oil (antimony trichloride). The thing is immersed in a solution heated to 50 ° C, and during the immersion, it is touched with a zinc stick.

Painted in metallic grey.

Very good staining gives a solution of the double salt of sodium sulphate and lead: dissolve 45 g of lead sugar (lead acetic acid) in 3/4 liter of water, and 150 g of sodium sulphate (hyposulfite) in 1/2 liter of water. Mix both solutions and heat to 85-93°C. The surface of a thing immersed in a solution is very quickly covered with a layer of lead sulfide. The color of this layer changes as it thickens and in the end becomes very beautiful - metallic gray.

Black staining with bismuth sulfide.

In a similar way, black staining with bismuth sulfide is obtained. To do this, the thing, painted, as explained above, with a brown bismuth nitrate solution, must be immersed while still hot in a strong solution of sulfuric liver (Hepar sulfuris) - the brown color quickly turns into black.

Paint Acrylic Brass - protective, decorative paint with metallic effect of brass. Resistant to UV and weathering, oils and gasoline. Possesses good adhesion and the increased color stability. Withstands temperatures up to 80°C. It is used on metal, plastics, wood and glass. Ideal for decorative purposes on metal structures, for painting gates, forgings, for protecting and updating the appearance of steel pipes, etc.

MODE OF APPLICATION. The surface to be painted must be dry and clean, free of rust and grease. For highly absorbent surfaces it is recommended to apply a sealing layer (e.g. emulsion paint). Shake thoroughly for 2 minutes. Spray from a distance of 25-30cm with side to side movements. Operating temperature 18-25°C. The coating will be dry from dust in 10 minutes. Full curing after 4-6 hours. Enough to cover approximately 3 m2.

ATTENTION. Pressure bottle. Protect from sunlight and do not heat above 50°C. Empty cans and waste must be properly disposed of. Do not pierce or burn, even after use. Do not spray on hot objects or flames. Keep away from sources of ignition. Do not smoke. Work in a well ventilated area. Do not breathe vapours. In case of contact with eyes, rinse with clean water. Do not allow to enter sewers and ground water. Keep away from children.

Manufactured by Eckart GmbH, Germany. Volume 400ml

Additional option

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When painting metal products, two goals are pursued: protection against the formation of corrosive areas and giving the metal an aesthetic appearance. Introducing the last task, sometimes it is necessary to cover the surface in 2-3 layers. But not always the end result can be just painting. Sometimes it is necessary to give metal products original decorative effects, for example, the look of an aged object. For this, special technologies are used. Let's try to figure out how to paint antique metal and what is required for this.

The effect of aged metal can be achieved by applying the main method - aging through the implementation of patina and the formation of scuffs. Patina is applied with special paints, but it is for metal that metallized acrylic-based compositions are more often used. In stores today, a wide range of such paints is presented, in addition to the decorative function, they also perform a protective task.

Acrylic paints for aged metal are available to choose from, namely for:

• brass;
• bronze;
• copper;
• gold.

Thanks to modern technologies, an aged effect can be given not only to metal surfaces. Often such painting is performed on plastic, wood and plaster products.

The aging process is completed by applying a final protective layer. For this, they often use:

• acrylic-based varnish, which has a high degree of gloss;
• very durable polyurethane-based varnish with a gloss degree of up to 50%;
• matt effect polyurethane varnish.

How to age metal yourself?

The choice of the method of creating an interior style, which implies the presence of traces of antiquity in the design, is quite wide. For connoisseurs of this style, it is not always affordable to buy real old items. The way out of this situation is to imitate ancient metals. How to paint antique metal with your own hands? Coloring is carried out in stages:

1. Surface preparation for painting. We get rid of dirt, rust and traces of grease by grinding and solvent treatment.
2. Metal priming. In this way, we achieve the formation of roughness on the surface for better adhesion of the paint. We choose a special primer for metal.
3. Application of selected metallic paint. Experts advise to carry out the process with a regular brush, so aging is achieved in the best way.
4. Aging stage. When the paint dries, cover the surface with a special craquelure varnish. It is after this step that the metal object is covered with cracks that create the effect of an old product.

Important! If non-metal surfaces are being processed, then it is necessary to responsibly approach the choice of primer composition to achieve reliable adhesion with metallic paints.

On the video: a master class on applying patina to forged metal.

Bronze painting

In the old days, many items were made of bronze. Therefore, painting products in bronze will help to decorate the interior of the house in the old style. There are several technologies for coating metal under bronze. Consider the simplest options.

Give a monochromatic effect

You can perform a one-color coating of metal with bronze as follows:

1. First of all, we clean the old surface from dirt and rust. To do this, it is necessary to clean it with sandpaper, and then degrease it.
2. To increase the adhesion of the dye to the surface, we perform the priming process for metal. In addition to adhesion, the primer will help to additionally protect the product from corrosion.
3. At the final stage, we proceed to staining with bronze paint. It is necessary to apply 2-3 layers evenly. But each subsequent layer is applied only after the previous one has completely dried.

Achieving antique bronze effect

Antique decorative painting with bronze effect is suitable for lovers of rare things. To do this, follow these steps:

1. The preliminary preparation of the old surface is carried out according to the same rules as in the previous case. Also, do not forget to cover the product with a primer.
2. After priming, one layer of bronze paint is applied to the surface. It is desirable that the composition be applied evenly, but for the effect of antiquity it is better to use a brush.
3. After drying, the bronze painted surface is covered with patina (darker paint). It is applied to the recesses. Experts advise using a translucent patina. This allows you to adjust the shade of the bronze finish.
4. The next stage is glazing, that is, processing with a brush, which is barely moistened with light paint. The process is carried out on all protruding edges and corners. This aging method allows you to give the product the effect of wear, which usually appears on the metal over the years.
5. Next, we wait some time, allowing the applied materials to dry completely, and at the end we cover the product with a transparent varnish.

Antique brass finish

Textured metallized compositions can transform the product, giving it an imitation of brass. The processing technology is almost the same as those provided above. The surface is preliminarily cleaned, polished and degreased. For aging, the technique of decorative painting under brass is used.

The application process is carried out as follows:

1. Before applying decorative paint, the old coating is removed from the product. To do this, you can use a metal brush or sandpaper.
2. The key to the strength and reliability of staining is the primer. Use a compound specifically designed for metal.
3. Brass paint is applied to the surface in one layer. You can age the resulting coating by painting with craquelure. Burnt umber, which is applied very carefully with a dry cloth, will help enhance the effect. If surpluses are formed during the work, then they must be removed before the substance dries.
4. Finally, the surface of the painted and aged part is coated with an acrylic-based glossy varnish.

As you can see, designer antiquity is achieved in simple ways. When doing do-it-yourself work, paints help to get the desired result, which create the necessary effect of a bronze, brass, copper surface.

Painting metal in bronze can not only protect the material from exposure to excessive moisture, which contributes to the appearance and spread of corrosion, but also give its appearance a fair amount of wealth and solidity.

To perform such work is available to anyone who has the necessary desire and a sufficient amount of time. We will consider the subtleties of this process in this article.

Choosing the right solution

Any bronze paint for a long time had an organic solvent in its structure. Its presence contributed to the spread of an unpleasant specific odor, which significantly limited the scope of such solutions.

In our time, thanks to technological progress, water-soluble mixtures have appeared that have natural metallic pigments in their composition. Acrylates act as binders in such solutions.

Bronze water-based paint (do not confuse - this is not Zinga electrically conductive paint)

Acrylic paint-bronze for metal has many advantages:

• Ecological cleanliness and the absence of any unpleasant odors. During the drying process, only water vapor is released.
• Relatively low price. The use of H 2 O as a basis makes it possible to make the production much cheaper, for example, of oil analogues.
• Stunning non-ferrous metal appearance. It is also possible to apply the “antique” method, which will create an even greater effect of naturalness.

• Easy to operate by hand. The application technology is slightly different from the use of conventional paint and is quite feasible for an amateur.

• Moisture isolation. Qualitatively protects metal from rust.

Tip: the pre-applied electrically conductive Zinga paint will allow you to protect iron from corrosion as much as possible, as it will create a reliable thin-film galvanizing layer.

• High resistance to mechanical stress and ultraviolet radiation. For many years, this finish will have its original appearance.
• Long service life. With proper operation for at least ten years.

Tip: if there are many fire hazardous objects in the room, it is recommended to additionally use fire-retardant paints for Polystil metal. They have the ability to foam when a fire occurs, preventing it from spreading further.

Paint application

First of all, careful surface preparation is required, the main stage of which is the removal of traces of rust. If you apply paintwork materials over places damaged by corrosion, then this will not protect the metal from premature destruction.

Preparatory work

The instruction is:

1. Remove old paint and rust.

To do this, you can use one of the following methods:

• Mechanical removal. A wire brush or abrasive discs are used. Only suitable for rough surface treatment.

Tip: Be sure to get your personal protective equipment before starting work. Metal dust, which will rise into the air during operation, is incredibly harmful to the respiratory system and human mucosa.

• Sandblasting equipment. High-pressure sand grains will perfectly cope with rust, scale and old paint, even in the most inaccessible places. The only negative is the relatively high cost of the device.

• Chemical reagents. Spray the surface with a special compound that will enter into a chemical reaction with the old lining and rust. After that, the remnants of the former coating are easily removed with rags.

1. We clean the iron from all the resulting debris, no matter what method of removal was used before
2. We apply a couple of coats of primer. So we will increase the adhesion of the metal surface and create an additional polymer layer of moisture protection.

After the last layer of primer has completely cured, you can proceed to the next step.

Painting

1. In the first case, you will get a monochromatic coating.

For this:

• We dilute the purchased mixture with water or white spirit according to the annotations attached to the jar.
• For small, extreme and hard-to-reach details, we use brushes. Flat areas are possible.

• If necessary, after the first layer, apply another one to create a more saturated color.
• We bring a bright light source to the applied finish. If no spots are observed, it means that the work was done with high quality, and you can enjoy the result.

1. If you want to create an aged, then you should paint in several layers:

• First, we apply a solid dark layer of metal or spray gun.