Steel bluing: description of the process, main methods

Blackening of steel with ferric chloride

It depends on what is considered ordinary steel
and what they said in chemistry lessons. poison in an acidic environment - get salt

Nothing precipitates if the ferric chloride solution is fresh and no printed circuit boards have been etched in it before. However, if the boards were etched, the steel will be copper-plated. The copper plating will be loose and easy to wear off.

To precipitate, as it always seemed to me, comes from the word sediment. So, an oxide film forms on the surface of the steel, and its composition (chemical formula), I personally like, the main thing is that the resistance to corrosion increases.

You know better

, he didn’t tell me that. And I didn’t know him.

I’ll try to say like a Sergeant: “You have been banned from Google. ?"(WITH)

, as well as correctly painted, glued, oiled. , you can continue for a long time, as long as your imagination is enough.

and by morning only phosphoric acid salts will remain on the hemp.

It is useless to argue with Vilenych (Udod) on this topic; he has a Nobel Prize in forging blades from shkh and rusting metals.

Sheb - if you don’t want to etch your blades, don’t etch, carbon and alloyed ones will give stains after the first use, nothing will suffer except aesthetics, just as etching will not add anything to the knife except aesthetics. and everything else is just lyrics on the topic. Sorry, but I’m tired of big names and “terms”

Well, how is it? Ferrous oxide is deposited, in theory. Among other things - but everything else must be periodically cleaned with a brush when etching.

50% at best, from experience with X12MF (and not CH, but orthophosphoric acid), with 65G and SH - much less. They recommend high-quality polishing of the entire surface of the blade - as a factor for minimizing corrosion.

Welcome to our weapons shop. There is no obvious heavy rusting, but... slowly, little by little, the blued trunks rust like nails

What will happen when etching aluminum in cold liquid? Is it collapsing? We need to remove the copper plating.

Source

Metal Blackening Technology

Blackening of metal is carried out in a certain sequence of actions:

How not to blue metal (and how to do it)

• First, chemical degreasing is carried out, which is necessary to remove residual grease and other contaminants from the surface of the product.
• Then washing is carried out, as a result of which the remaining alkaline solution is removed.
• Next, the part is etched by immersing it in an HCl solution. And again the washing is done.
• The next stage is activation, when the product is immersed in a solution with special additives for several minutes.
• Afterwards the part is washed again.
• Then a black mixture is applied to the engraved metal surface and fired. This composition, in molten form, evenly fills the design, giving a subtle contrast with the rest of the surface of the product.
• Next, the part is immersed in a bath of cold water for half an hour or an hour.
• At the very end, the product is sealed with a special inhibited water-repellent compound to protect the metal from rust.

V. BLUE BLUEING

On iron metal it is possible to reproduce a wide variety of tones, shades and nuances of blue - from blue to blue-black inclusive.

The simplest way to chemically color iron and its alloys is direct heating in air, surface oxidation with atmospheric oxygen. This is how bluing is done in faded colors, which we talked about in the previous chapter. Among the range of tarnish colors, blue-colored colors appear. Only through long-term experience can one achieve in each given case (for a certain size and shape of products and a certain material) the establishment of conditions under which the same color tone is always obtained. When constantly working on the same products, you should definitely stick to the once-tested heating recipe, almost certainly achieving the desired result every time.

It should always be borne in mind that smaller things heat up to a certain temperature faster than larger ones, and therefore both of them should never be heated at the same time in a common bath or at all together; There is always a risk of “over-burning” (that is, going beyond the blue color) of small products and under-exposing (not reaching the required blue tone) larger ones.

In practice, the easiest way to achieve uniform heating of small objects blackened in large quantities is to enclose them in an iron drum (equipped with holes), which is rotated on a spit over a hot coal forge. The holding time of things in the drum is learned from experience. During operation, you can monitor the end of heating by minutely removing the sample for inspection. Heat bluing is a “dry” processing method. For wet bluing of iron and steel to a uniform blue color, the following tested bath (1) is used:

Bath composition 1

To prepare it, dissolve red blood salt and iron sesquichloride separately in 500 g. water and both solutions are poured into one bottle.

The products to be settled are immersed in this bath for the time necessary for the required color tone to appear.

Dark blue color on iron and steel is applied to the bathroom (2):

Bath composition 2

Both salts are dissolved in water separately, and both solutions are mixed. When used, carefully heat the bath, slowly bringing it to a boil. In this case, iron and steel objects are covered with a dark blue coating (lead sulphide). Once the correct tone is achieved, the products are removed, rinsed with water, dried and placed in a warm place for a few more hours.

Hot baths of molten (rather than dissolved in water) reagents are also recommended. One of them (3), especially suitable for small products made of malleable iron and cast iron, is composed of molten (cut) sulfur, into which a little soot is mixed after melting. When processed in such a bath, the products are covered with a film of iron sulfide, which acquires a beautiful dark blue polish from brushing (brushing).

Another bath (4) is molten saltpeter (temperature about 315°). Its action is obviously based on the oxidation of iron with oxygen released during melting by saltpeter.

Metal blackening

The blackening method is used to cover metal products with a beautiful, uniform black decorative film, as well as to protect them from tarnishing, corrosion and mechanical damage. Today, this simple and very affordable method of metal processing is in demand in various areas of industrial production , as well as in jewelry and all kinds of crafts . To decorate with niello, a mixture of silver, lead, copper and sulfur is used in different proportions.

JUST SUPER - BLUEING OF METAL WITH LYE LOOK

There are many different methods for blackening metals:

Metal bluing. Two ways - citric acid and oil. What's better?

• Oxidation is a process in which metal surfaces are treated with liquid sulfate solutions;
• Galvanic blackening - processing of metal products with electrolyte;
• Firing in oil - surface treatment using the method of incandescence of a metal product;
• Thermal blackening is the treatment of a product with vapors of a special chemical composition.

Burnishing or oxidation, or blackening, or blueing

VI. BROWN BLUEING

A good brown color on iron and steel is achieved by bluing using a paste (5) from a mixture of equal parts of olive and antimony oils:

Recipe 5

This paste is applied to the object to be harrowed (usually gun barrels are blued with it) and left for 24 hours, after which it is washed with a woolen rag and a fresh portion is applied, which is also left for 24 hours. As a result of the chemical action of the paste on the iron of the object, a bronze-brown film of iron oxide (containing metallic antimony) is formed, firmly fused with the bulk of the metal. Thus, polished products are given a gloss by wiping with a waxed brush.

For small items, you can reduce the two-day processing time with this paste to just a few minutes by heating the items coated with the paste to 200-220°. Olive oil can be replaced with flaxseed oil. Usually, coating twice is sufficient. For large products, this method is practically inapplicable due to the difficulty of uniform heating; The coloring on them is usually spotty.

Some practitioners impart a brown bluing to iron and steel by heating objects coated with animal (usually ox) fat for 1/2-1 hour to a temperature of 200-100° (6). Fats are often replaced with vegetable oils, such as flaxseed (7). For darker tones, add sulfur color to the fat (8).

Instead of antimony trichloride in recipe (6), you can take iron sesquichloride, for example in the ratio (9):

Recipe 9

Having coated an object with this ointment, let it act for several hours, after which its surface is brushed with a steel brush, coated with ointment again, brushed again, and so on. Kratsovka must be carried out especially thoroughly.

The shades have a greenish or reddish tint, depending on the predominance of olive oil or chemicals in the composition.

Dipping baths (for turning steel and iron brown by dipping) can be prepared from iron sesquichloride, dissolving it in water or alcohol.

Water bath (10)

alcohol bath (11)

Methods for bluing weapons at home

keeping hunting weapons in order is the responsibility and concern of every owner. Maintenance requires some effort, but for true lovers it is not a waste of time. The ability to extend the service life and eliminate the appearance of traces of corrosion, shells or other defects on gun barrels is of great importance for successful hunting and the owner’s own safety.

The traditional way to protect weapon metal from rust is bluing, which has to be done from time to time. Coating application is a technically simple procedure, but requires considerable experience and skills. Many owners blue their weapons at home, which saves time and provides the highest possible quality of protection.

Sometimes this option is the only available method of coating, so it is useful for every owner of a hunting rifle to have an idea about it. Let's consider what this procedure is and how accessible it is for independent implementation.

What is bluing?

Burnishing is the application of a thin film of oxides to the previously prepared surface of steel or cast iron parts, protecting against corrosion and giving the metal a bluish-black color. The thickness of the film ranges from 1 to 10 microns; the thicker it is, the deeper and darker the color of the coating.

The classic method of bluing, used for several hundred years, is to apply drying oil or linseed oil to the surface of heated metal. The result is a fine-crystalline coating that has protective anti-corrosion properties and a pleasant blue-black color. It is customary to judge the heating temperature by color, although this method is not very accurate.

The blue color, most suitable for bluing, appears when steel is heated to 300-320°.

The coating obtained in the traditional way was not distinguished by proper strength, durability, and did not provide complete protection against rust. Over time, other, more effective methods of bluing metal were developed.

Most of them were created specifically for weapons, since the specific service of weapon metal did not allow other finishing methods.

One of the reasons for the need to use other coating methods was the task of abandoning the heating of weapon barrels, which had a negative impact on the condition of the metal, its physical and chemical properties.

What is it used for?

Initially, the procedure was carried out solely for the purpose of protection against rust, since there were no other types of coating, and the operating conditions of the weapon greatly contributed to the development of corrosion processes. Currently, in addition to its protective functions, bluing is considered as a decorative coating that gives weapons a traditional look.

It is noteworthy that the appearance of a weapon is considered by a large number of owners to be one of the most important components of its performance, while protection against corrosion is not considered a problem at all. However, all currently used types and methods of bluing provide a sufficient degree of protection of the metal surface from moisture.

It is also necessary to understand that any bluing agent does not create a coating layer, but only promotes the formation of a reaction as a result of which this layer appears on the surface of the metal.

Types of bluing

There are the following types of metal bluing:

• alkaline . The steel surface heated to 135-150° is covered with a thin layer of alkaline solutions, causing an oxidation reaction and the creation of a protective film;
• acidic _ Produced by electrochemical or chemical methods using acid solutions;
• thermal _ Refers to traditional methods of bluing, although there are more modern technologies with the formation of protective films in vapors of ammonia-alcohol compounds or in molten salts.

There are a huge variety of methods for applying protection, from complex multi-step processes to simpler and faster procedures. All of them are characterized by a limited period of validity and do not provide absolute protection from moisture.

The barrels of hunting rifles must be blued from time to time, and the condition of the weapon must be constantly monitored.

Coating cannot be considered as a final solution to the problem; it is only a way to somewhat reduce the consequences of contact with water and slow down the rate of rust formation.

What methods are available to perform at home?

Complex technological operations are not possible at home, but simpler procedures are quite possible. There are several basic bluing methods:

• cold;
• hot;
• oxidation.

All three methods can be done at home, for which you need to acquire all the necessary materials and equipment, as well as study and understand in detail the physical and chemical essence of the processes. It is not recommended to get down to business without understanding the meaning of the operations being performed. Any method consists of the same steps:

1. Cleaning, removal of old coating and rust.
2. Grinding, removal of cavities, small scratches, dents.
3. Degreasing. The surface layer of fat is removed, for which various chemical reagents are used. After completing this stage, work with metal only with rubber gloves.
4. Actually bluing.
5. Finishing the metal surface.

The most important point (apart from the coating itself) is degreasing. After this you can start bluing. Let's consider the possible options.

Cold bluing

The principle of cold bluing is simple - a special liquid is applied to a previously prepared surface. There are ready-made formulations:

• raven 3;
• Parisian oxide;
• rusty varnish.

The first two products are sold in stores. With the third, the matter is more complicated - in its finished form it is stored for a long time, but it is practically never on sale, there are only advertisements for the sale of old stocks. Making rusty varnish is a complex and dangerous procedure, since you have to mix 50 ml of hydrochloric and 54 ml of nitric acids, 30 g of steel or cast iron filings, and 20-30 g of scale.

All this is dissolved in 1 liter of distilled water, not immediately, but gradually:

1. A third of nitric acid and a third of chips with scale are carefully poured into hydrochloric acid. The reaction will begin, you must wait for it to subside.
2. Repeat the procedure and wait for the end of the reaction again.
3. Pour out the remaining chips and scale, pour out the last third of the nitric acid. Seal and leave for a day. Then add a liter of distilled water to the resulting brown solution, after which the rusty varnish is ready. You can use it for a long time, it becomes harmless and does not require special precautions.

The composition is applied with a regular brush . It is necessary to ensure the uniformity and penetration of liquids into all corners and crevices of the parts. After finishing the work, the part is washed and polished.

Hot bluing

This method is the easiest. First, the part is heated, after which it is immersed in oil (as an option, the surface is smeared with a swab dipped in oil). The best option (as it is believed) is linseed or hemp oil, somewhat worse - drying oil.

Mineral (machine) oil can also be used, but after it the results are considered the worst. Some masters advise waiting a while after applying the oil, then removing the excess.

Others recommend baking the butter with a blow torch, which creates a thick black coating.

There is definitely no best recipe, since everyone has their own conditions for heating and applying oil, different temperatures and other nuances that affect the result. Everyone agrees on one thing: after the first application of oil and a short exposure, it should be thoroughly wiped off.

This allows you to remove residual fats, which in any case cannot be dissolved during degreasing. The procedure of heating and applying oil is then repeated several times until the best result is achieved.

VII. BLUE GRAY COLOR

For bluing in a gray color, you can use a bath of a relatively complex composition, but which allows, depending on the duration of treatment of iron and steel products with it, to obtain various variations of gray color with a transition to black.

Bath composition (12)

First, mix the acid with water, pour in alcohol and dissolve all three named salts separately in three separate portions of liquid, after which the individual resulting solutions are poured together.

Objects brought into this bath must be absolutely clean and free of grease. The products pickled in it are then transferred to boiling water for half an hour. If the shade is not dark enough, repeat the bath treatment. After drying, the products are wiped with a waxed brush. A beautiful, firmly adhering gray layer (consisting of copper oxide) on small iron objects can be caused by heating them on a sheet of tin after coating with the composition (13).

Recipe 13

The dissolution of copper nitrate in alcohol in the cold takes a very long time. It is more expedient to carefully melt the salt over low heat (in a porcelain crucible), add to it (putting out the fire) the required amount of alcohol and quickly cool while stirring.

Methods for quickly oxidizing weapons. Self-blueing. Plastic stock

Before oxidizing, the trunks must be completely cleaned and completely degreased, otherwise the oxidation will turn out uneven, with stripes or reddish spots. Such a complex procedure requires a lot of time and the work is expensive.

Initially in America, then in France and other countries after 1918, they began to use a new method of rapid oxidation of weapons using the Parker method, so rapid oxidation began to be called Parkerization .

The new method consists of immersing weapon parts in a bath of boiling composition, boiling for 30 minutes to 1 hour 30 minutes, rinsing in clean cold water, and oxidation is ready. With all this, the survivability of the new oxidation is no less than the survivability of the previous oxidation, and working with the new method is much cheaper than the previous one. The following compositions are used for parkerizing weapons.

All parts made from brass can be given a beautiful dark color through oxidation, which also protects the brass parts from the usual “greening” of brass. Oxidation is performed as follows. Take 10 g of copper carbonate or a piece of malachite (Ural mineral) weighing 10-15 g; malachite is turned into powder and poured into 100 g of ammonia (25 percent ammonia); At the same time, a piece of brass (0.25 g) is dipped into ammonia. Shake the mixture well and after some time repeat shaking 2-3 times.

The brass part is well cleaned with sandpaper or a “velvet” file, or degreased with Vienna lime, then dipped into the solution (on a piece of brass wire or strong thread) and kept in it until the desired darkening, the latter occurs within a few minutes. You should not keep the part in the solution for a long time, as the composition corrodes the brass, causing it to become brittle. Having removed the part from the composition, rinse it thoroughly with water and dry it, wiping it with a soft cloth.

Parker oxidation method

Parker's method. Take a 60% solution of orthophosphoric acid, put iron and steel filings into it and let it stand for several days (5-15), the longer the better, because the sawdust dissolves slightly. It is desirable that the composition be more saturated with iron. The solution should be in a sealed glass container.

The weapon to be oxidized is then boiled in the solution for 30–45 minutes. It turns out, depending on the type of steel, dark gray or matte black. The preparation of objects to be oxidized is very simple: you just need to degrease them, there is no need to remove the old oxidation or bluing, a new solution will remove the old bluing and give it its own tone. The weapon parts removed from the solution are rinsed in cold water, dried and lubricated with gun oil. The weapon is boiled in an iron vessel.

Positive qualities of parkerization: = it gives a matte rather than shiny oxidation (matte oxidation camouflages weapons better); = oxidation is very strong, tenacious, and protects iron and steel well from rust;

= the composition is almost harmless to the worker, not dangerous to hands and clothes, and only when boiling the steam is it advisable to let it go into the exhaust pipe.

When parkering weapons, care must be taken not to overcook the weapon: if the weapon is boiled for too long and if the composition is too strong and not saturated with iron, then the oxidized surface will corrode.

Barrels soldered with tin solder should not be parkerized, because the composition will dissolve all the solder. However, only the barrels of older systems are soldered with tin; the newest two-barreled shotguns, which have a barrel under the barrel, are no longer held together by soldering, they have a mechanical connection, therefore they are harmlessly oxidized using the Parker method. There are other compositions for rapid oxidation of weapons.

To remove oxidation, the product is hung on an anode rod in a bath with a 15-20 percent caustic soda solution. Anodic etching is carried out at room temperature and an anodic current density of 10-15 A/dm2. The cathodes are steel plates. The presence of chlorine ions, which contribute to the dissolution of the base metal of the part, is not allowed in the solution.

Independent bluing of part of the weapon, or the entire barrel

Metal bluing: 1. Immerse the barrel of the weapon, or its metal part, in a concentrated solution of caustic alkali containing sodium nitrate. Heat until almost boiling. The thickness of the black film will be up to 1.5 microns. when repeated twice. After this, rinse and dry, and plunge into oil for 5-7 minutes at a temperature of 105 - 120 degrees.2. Heat the metal until it turns crimson and rub it well with the onion head.

Plastic stock

A plastic stock turned out to be a serious competitor to wooden and metal stocks. Such stocks were tested by Belgian gunsmiths until 1939. Tests have confirmed that a plastic stock has undeniable advantages over wooden and metal stocks. Firstly, special grades of plastic are much stronger than wood: its strength is close to that of a good horn. Therefore, a plastic stock is more durable and durable than a walnut stock.

Plastic is somewhat lighter than walnut and much lighter than aluminum, and also lighter than products made from porous “AMC”, as a result of which the plastic stock is quite light. At the same time, thanks to the great strength of the plastic, such a stock can be made even lighter by making a partially hollow butt, where you can arrange storage for small accessories.

A plastic stock, even under the most severe conditions of service, does not lose its new appearance, while a walnut stock, with frequent use of the gun in any weather, requires annual refreshment (finishing with wax or polish), and at the same time, the carved scales on it are wiped off and worn out , not all nicks and dents can be removed, etc.

The plastic surface, being much stronger than a wooden surface, is less susceptible to external damage.

A wooden stock requires a metal frame for reinforcement (butt plate, extended trigger guard tail, etc.). With plastic, such parts are no longer needed. This simplifies and reduces the cost of gun production. If the trigger guard is made of plastic, then when carrying the gun in your hands in the cold, your fingers will freeze less. After all, a horn trigger guard is made for this purpose.

The main thing is that plastic is not afraid of rain, water, dampness, does not retain moisture and does not spread it to the steel parts in contact with it, causing corrosion, as happens with wood. When dry, the tree often gives in to the leash, resulting in a less sticky stock. This does not happen with a plastic stock. Finally, the material and production of a plastic stock is cheaper than a wooden one. The plastic stock is made by pressing. The appearance of such a stock is very decent, because the plastic is made of a dark walnut color with a pattern similar to the twisted structure of the best butt nut.

During the war 1941–1945 The Germans used this stock for light machine guns, probably borrowing it from Belgium. In modern mass machine production of guns, a plastic stock turns out to be indispensable: it makes it possible to produce inexpensive, durable, elegant and extremely durable guns. In addition to stocks of standard designs and sizes, each factory may have a small stock of stocks of special sizes for guns for individual orders. Very few of these guns are made. The main thing for production is mass standard samples, not single orders.

In addition to hunting rifles, plastic stocks are highly desirable for sniper rifles. It can be assumed that in the near future the fragile wooden stock - a legacy of the ancient wooden arquebus machine - will be replaced by a new, more advanced stock made of better plastic.

Markevich V.E. "Sporting and hunting small arms"

Source: https://www.shooting-ua.com/arm-books/arm_book_165.htm

VIII. BLUE BLUE

In factory practice, iron and cast iron objects are blued, forming a relatively thick layer of black scale (iron oxide) on them. For this purpose, they are heated to a cherry-red heat in regenerative furnaces, and alternately (6-10 times) either flue gases or flue gases diluted with air are introduced (for heating).

Another factory method is a long (5-10 hour) treatment of products with highly superheated water steam.

In amateur and artisanal practice, these methods are unlikely to be applicable. In an amateur workshop setting, you can achieve a great richness of black shades using another method of hot bluing, which involves burning fatty substances such as lard, vegetable oils, waxes and the like on the surface of the product. So, if you burn a well-prepared (cleaned, degreased, pickled and washed) iron product, greased with linseed oil at a dark red heat temperature, it will turn shiny black (14).

This method of bluing is very widely used in practice. In order for fats, oils or waxes applied to products to adhere well to their surface, it is recommended to heat the product so much before coating it that a pale yellow discoloration appears. Lubricated objects should be held over the heat of a coal forge or in a suitably hot oven (“air bath”) for so long until all the oil evaporates or burns out and the smell disappears from it, and the surface of the object seems completely dry.

Some features

Blueing steel at home is not difficult. Oxidizing agents are used for processing other metal products:

• cast iron;
• copper, which acquire an intense red color.

There are a number of features that it is advisable to remember:

1. If the products are heat-sensitive or hardened, then it is better not to touch them. Blueing will degrade performance.
2. To complete the process, you must remember to wash the product with a special product. After drying, oil lubrication is sometimes required.
3. It is not difficult to find the necessary substances in stores, for example, saltpeter, citric acid.
4. It is also possible to remove blackening. For this you will need a special pencil.

Preparation is important:

1. Before starting, you need to clean the surface and sand it.
2. Degrease with a special solution.
3. Don't forget about rubber gloves to protect your hands. The processed product must not be touched.
4. Create ventilation, exhaust.
5. Select a vessel with suitable properties. The volume should allow the product to be processed to be completely drowned. A material that is not afraid of the substances used is suitable: glass, porcelain, stainless steel, earthenware.

As for color, it can also be important for some products. You can get different colors: from yellow to black, its shades. Therefore, strictly speaking, blackening and bluing are not the same thing.

To achieve the desired color, you will have to further clarify the components of the solutions or pay attention to the heat treatment mode. For example, one way is as follows:

1. Take copper nitrate (70 g) and alcohol denatured alcohol (30 g).
2. The salt is heated until it melts.
3. Add denatured alcohol.
4. The product is coated with this mixture.
5. Heat until the desired shade is obtained. The color will change.

IX. BLUING WITH BRONZE SHOW

Iron and steel can be burnished in a variety of colors (blue, crimson, brown, black) with a more or less clearly defined bronze tint. The methods related here are combined under the name “chemical bronzing”.

Bronzing blue (35). A well-prepared blackened object is placed in vinegar (diluted acetic acid). After removing it from the vinegar and wiping it dry, lubricate it with hydrochloric acid using a linen cloth. After 15 minutes, they are buried in the sand of a heated sand bath, from time to time, exposing part of the surface of the object to observe its condition. As soon as the moment has arrived when the surface has taken on a beautiful, uniform, deep blue color, the object is removed from the sand.

Bronzing in brown color. By rubbing objects treated as above (bronzed blue) with “wooden” oil (on a cloth), you can transform the blue “bronze” into brown (36).

Another way is this. The objects to be bronzed are exposed to vapors of a heated mixture of conc. for 3-5 minutes. hydrochloric and nitric acids (the so-called “regia vodka”; extreme caution is required when working with it, because this mixture of acids when heated is extremely dangerous and its vapors are especially harmful!), after which it is heated to a temperature of 300-500 ° for so long until a bronze tint will not appear on the surface of the products. After cooling, the product is rubbed well with Vaseline and heated again, increasing it until the Vaseline evaporates. After allowing it to cool, rub it with Vaseline again, this is how light brown tones are obtained (37).

By adding acetic acid to aqua regia, you can obtain bronze colors of yellow-chocolate tones using the described method (38).

"Hot" bluing

Advantages

• This coating lasts much longer.
• The absence of harmful fumes that accompany the process of “cold” bluing.

Technology

The workpiece to be processed is first slightly warmed up so that the substance “fits” better onto the base. You can use gun oil, linseed oil, lignite oil, olive oil, or something similar. The choice of a specific product depends on the type of metal.

How to apply oil is up to everyone to decide for themselves. It would probably be more advisable to dip the part into it. After this, it is subjected to heat treatment. The most common method is firing with a blowtorch.

Feature of the technique

• After immersion in the bath, you need to let the oil drain. Excess of it will lead to stains on the surface of the part.
• During the firing process, it is necessary to control the color change of the workpiece. Once it changes from brown to black, treatment should be stopped.

Burnishing with oxidizer

Various chemical compounds such as nitrites or nitrates are used. All of them are characterized by their melting point, so you need to focus primarily on your own capabilities, since not every owner has, for example, a muffle furnace. Temperature sources can be different, so there is no need to complicate your life and be guided by the first recipe you come across - the choice of oxidizing agents is quite large.

X. BLUEING OF RIFLE BARRELS

A particularly common case of chemical coloring of steel is the bluing of gun barrels. The purpose of such bluing is the usual - to give the barrel a beautiful appearance, protect it from rust (especially if the gun is rarely used) and eliminate the need for frequent cleaning.

There are a fair number of recipes for bluing gun barrels, partly repeating the methods described above, partly specially adapted to the special shape and special service conditions of the product. The choice of one or another of these recipes depends primarily on the color nuance that is desired to be obtained, on the ability to obtain the necessary chemicals, on the strength of the color, and the like. Complete mastery of a particular recipe is a matter of long, persistent experience. One cannot reject a particular recipe if at first it does not produce favorable results; You should always check the entire progress of its execution in order to detect and correct very possible errors. With due diligence, you can not only extract from the recipe all that it can give, but also improve it yourself, achieving more and more excellent results.

A mandatory, strict condition for successful work here, as in all cases of chemical coloring of metal, is exhaustively complete, ideal preliminary preparation, as well as subsequent processing. Due to the significant size of the trunks, all techniques suitable for processing smaller and more compact objects cannot be used to work with them. A tarred trough of appropriate size and shape can serve as a vessel for treating trunks with certain liquids. Only the outer surface of the trunk is blued, the inner surface is not treated, and the inside of the trunk is protected from the action of the compounds by plugging both end holes with tightly driven wooden plugs. The protruding ends of these plugs serve as gripping points for clamps or vices when strengthening the barrel to perform various operations related to chemical painting (scraping, grinding, polishing, coating, washing, brushing, and so on).

Here are several more or less commonly used recipes for bluing barrels.

(39). The barrel is heated to intense heat and rubbed with bloodstone for a long time, renewing the heating when it cools. The result is a bluish coloration.

(40), A well-polished trunk is rubbed with olive oil using a cloth, after which it is sprinkled with sifted ash from hardwood and introduced into the charcoal mine. When the trunk noticeably turns white, it is removed and allowed to cool, after which it is first wiped dry, then with olive oil. The barrel gets a gray bluing finish.

(41). 4 parts by weight of antimony oil (antimony trichloride) are heated with 12 parts by weight of olive oil until both substances are completely dissolved and the resulting mixture (on a cloth) is rubbed on the blackened barrel. A day later, the resulting deposit is wiped off by rubbing with oil and the lubrication with the composition and rubbing are repeated again. After another day, the described operation is repeated again, and so on. After 10-12 days, a uniform, firmly adhered color of chocolate, brownish red, or even brown is achieved. Operation goes faster in warmth.

Once the desired tone is achieved, the barrel is wiped down, thoroughly washed with water and either polished with a steel polishing pad or waxed with suede. You can also coat it with shellac varnish (42). Prepare the following composition:

Recipe 42

All this is mixed (pouring the acid into water, and not vice versa!) and allowed to stand after dissolving the copper sulfate for 2-3 days. Having tightly plugged both holes of the barrel with wooden plugs, coat it (using a sponge) over the entire surface with the prepared composition, trying to ensure that it lies evenly everywhere. A day later, use a brush to scrape off all the loosely adhered part of the film (oxide) formed during this time and repeat the described operation once or twice until a thick brown color is obtained. Then the barrel is wiped and dipped in boiling water containing a little soda (to neutralize traces of acid). After being removed from the water and dried, it is gently rubbed with a wooden polishing pad (made of hard wood), heated to 100° and doused with alcohol shellac varnish, painted with dragon’s blood (see “Varnishes and varnish paints”). After the varnish has completely dried, polish it with a steel polishing pad to give the barrel a pleasant shine.

(43). For bluing iron trunks brown, a solution is prepared.

adding acid and alcohol after dissolving the vitriol. Using a sponge or the like, lightly apply this solution to the prepared barrel and, after complete drying (after several hours), wipe it with a brush made of the thinnest wire and then with a stiff bristle brush. All this is repeated 2-3 times every day and after 3 days a beautiful shiny brown bluing is achieved. For final finishing, the barrel is washed in boiling water, wiped with cloth and lightly greased with olive oil.

(44). Prepare the ointment by rubbing both components:

stored in closed jars.

The prepared trunk is heated and, when heated, is coated with this ointment (using a linen cloth). After 24 hours, wipe with a soft brush and coat again with the same ointment. This is repeated until the color of the trunk, which first became greenish and then reddish, becomes clearly brown. This happens after 4 - 6 days (the warmer, the sooner). Next, the barrel is thoroughly washed with lye until the latter evenly wets the entire surface. After rinsing several more times with clean water, dry, polish with a wooden polishing pad or rub with a soft brush, heat to 100° and pour over the above varnish.

(45). A very beautiful bluing is obtained when using the composition:

If the solution turns out to be opaque, add hydrochloric acid drop by drop until clear. Lubricate the barrel with this solution, repeatedly applying it 3 to 4 times each time. Finally, after each lubrication, wipe with a soft brush. In total, lubricate 12-14 times, using it for 3-4 days. The process is accelerated by weakly heating the barrel.