Hot burnishing of metal at home. Burning a knife in citric acid

Meanwhile, from time immemorial, in order to solve such problems, as well as to provide protection metal products from tarnishing, the blackening method was used. The history of this type of metal processing has more than a dozen centuries.

It is believed that in Rus' this technology came into use thanks to the Khazars, who knew how to blacken weapons, giving it a noble look. Today, blackening is still in demand in various areas of industrial production, but is most often used for decorative purposes in jewelry and various crafts - blacksmithing of all kinds of products, chasing, and weapons.

The essence of metal blackening is to obtain on its surface a sufficiently strong and durable coating that is resistant to mechanical, physical and chemical influences. It has pretty good protective functions, as it prevents the contact of the metal with moisture. Therefore, rust on blackened products forms much longer, which allows to increase their service life.

In addition, black-coated metals have a noble matte sheen that does not fade over time. True, it should be noted that with prolonged use of such products, the black is still erased. This is especially noticeable on the barrels of firearms, which periodically need blackening to protect the metal and restore the aesthetic qualities of products.

There are many various ways blackening of metals, which are successfully used both in industrial production and in everyday life. The oldest of them is considered to be oxidation, which is the treatment of metal surfaces with liquid solutions of sulfates, due to which a thin black oxide film is formed.

This technology is still widely used in industrial production today, but in domestic conditions it requires certain safety rules to be observed, since oxidizing compounds often contain aggressive chemicals, such as hydrochloric acid.

In addition to oxidation, in industrial conditions, the galvanic blackening method is successfully used today, thanks to which, with the help of an electrolyte, a thin and durable layer is applied to metal surfaces, which simultaneously performs protective and decorative functions.

The most ancient methods of blackening metals include burning them in oil. For these purposes, metal products are first heated red-hot, so they are immersed in an oil solution and heated again over an open fire until the oil is completely burned out.

If you repeat this procedure several times, then the products acquire a noble black color. True, this technology today, as a rule, is used only for domestic and decorative purposes, since the niello obtained in this way has rather weak protective functions.

More modern technologies make it possible to carry out blackening of metals in industrial conditions by the thermal method, when products are treated with vapors of molten salts, a mixture of alcohol and ammonia, as well as oil varnish.

As for jewelry production, nowadays blackening of silver can be done not only by chemical and galvanic methods. The simplest and most affordable option is mechanical blackening using a graphite mixture, which is rubbed into the relief surface of jewelry, emphasizing the beauty and originality of their pattern.

Steel burnishing can be considered an industrial-scale process. It involves the application of a protective layer on the product or surface - iron oxide, which has certain characteristics. But bluing at home is also done quite often. It cannot be compared with the oxidation process in a factory, but this technology is successfully used in practice by home craftsmen. There are several methods of bluing, among them hot, cold methods and the method of exposure to oxidizing agents can be distinguished.

cold way

Burning at home can be done by a method that does not involve hot processing. It is applicable in the event that metal parts cannot be subjected to significant loads. Among the solutions that can be found in the arsenal of a home master, there are those that can form a special protective coating on the metal surface. One of these is the so-called Paris oxide. Its application should be carried out with a brush, and then wash the surface or product. This process cannot be called long or costly.

If there is a need to achieve a longer effect, then the treatment can be carried out by the method of complete immersion in the solution. After that, the part or surface should be washed with any means, wiped with a rag, which should first be moistened with alcohol. If such burnishing at home was done independently, then you can check its effectiveness with ordinary water. Moisture is applied to the base with a brush, after which not a drop should form, but a uniform film.

hot way

If the metal can be subjected to high temperatures, then it is first tarred and then fired with a blowtorch. For the process, you need to prepare weapons or olive oil. This technology is effective, harmless and low-cost. It is worth noting that the effect lasts much longer than when processed in the above way. During the work, heating should be carried out slowly, everything starts at 200 degrees, and ends at around 400 degrees. If such bluing at home is done by you yourself, then a brown layer forms on the surface, and then a black layer. It is important to avoid using too much oil, otherwise stains may form on the surface.

If metal bluing is to be carried out at home, then the best method for hot working is a composition that is prepared from 20 parts of grease and one part of sulfur. The resulting mixture should be applied to the surface as thinly as possible, and then the craftsman subjects the product to flameless firing. The formed film will become perfectly uniform.

Blueing with oxidizers

This method involves the use of molten oxidizing agents, these can be nitrites or nitrates. The metal part should be lowered into the molten salt, holding it there until the surface becomes black. Instead of these substances, which are quite dangerous, alkaline or hot saline solutions can be used.

What else does a master need to know?

Burning metal at home can be done quite simply, as evidenced by the above recommendations. Oxidizing technology is a method that is widely used for blackening copper, cast iron and steel products. The former acquire a rich red color after the completion of the process. But if you are faced with the task of blackening hardened and heat-sensitive products, then it is not recommended to process them using this method.

We should not forget that after the bluing of the gun at home has been completed, it must be washed with special products, dried, and then lubricated with oil.

Burning features

In industrial conditions, the burnishing of the upper layer of metal is carried out by changing the structural composition. Among other things, a protective coating is applied in a special way, which contributes to protection against corrosion. Apply at home technologies that are used on industrial enterprises, is not only economically unprofitable, but also impossible. You can deal with rusty metal yourself by applying compounds that are sold in a wide range in stores of related products. A sufficiently high-quality result can be achieved by using saltpeter. Among other things, blackening can be effectively removed using a special pencil. In some cases, steel bluing at home is done with citric or phosphoric acid.

Secrets of the work

Initially, you need to make a thorough grinding and cleaning of the surface. Then degreasing is carried out, for which a special solution should be prepared. The selected agent is applied in the next step. After the degreasing is completed, the product must not be touched, otherwise all work must be carried out with rubber gloves.

Conclusion

Burning trunks at home, as a rule, involves the application of substances that are classified as dangerous. That is why the master must follow the rules and provide special conditions that guarantee safety and exclude injury. Due to the fact that the solution used for bluing contains chemically active components and acid, it is necessary to use only special containers. This will prevent damage to materials in products and will not cause you unnecessary trouble, which is very important for the successful completion of work.

Burnishing is the process of producing an oxide layer several microns thick. It is also called oxidation, blackening or blueing. This is a dark, almost black finish, but there are other shades.
Basically, burnishing is used as a decorative coating, but initially, first of all, it is designed to protect steel from corrosion.

I will show you how to make a simple knife bluing at home, using all the components available to everyone.
What will be needed?

• - Boiling water 0.5 liters;
• - Citric acid 50 grams (available at any grocery store).

Knife burnishing process

• - Every 10 minutes, take out the knife and wipe the blade with a soft paper or cloth napkin, removing black deposits from the surface.
• - Approximately every 1-2 minutes it is necessary to move the blade in the solution, thereby dumping large gas bubbles from the blade. This will ensure uniform coverage.

Steel bluing is increasingly used for painting metal products. It provides reliable protection surfaces from rust and decorative finishes. With the chemical version of staining, a protective shell appears on the surface. In the process, oils and acids are used. Depending on the type of material used and the degree of heating, the metal joints acquire a natural shade.

Many people think that this processing option is used only in the factory. But it can be organized independently if you follow the sequence of actions and use the right tools.

As a result of the work done, a film of iron oxide will appear on the surface. The dimensions of its thickness are completely dependent on the technology used. It can be 1-10 micrometers. Using the metal burnishing method, you can solve the following problems:

• protect the coating from corrosion, since rust does not appear on blued surfaces;
• give the product a more presentable appearance.

You can get the desired coverage in many ways. But the most popular of them are alkaline, thermal or acid bluing. Alkaline processing is ideal for independent work. To do this, you will need water, a digital scale, sodium nitrate and sodium hydroxide. You will also need a protective mask and gloves for personal safety.

Use only stainless utensils for work. Blueing of steel is carried out under certain temperature conditions. The solution is maintained in a boiling state, which is why it must be handled with extreme care.

To create a durable steel coating at home, the process lasts at least 1.5 hours. Before proceeding with blackening, the surface must be degreased with a solvent. Colour protective film is determined by the warm-up time, as a result of which it will constantly change. To avoid a strong difference in shades, the surface is completely immersed in the solution.

Important! After processing, metal products must be thoroughly washed in soapy water.

Popular bluing methods

Burning technology includes several methods, the main of which are the following:

• Alkaline method. In this case, you will have to work with oxidizing agents in compliance with the temperature regime of 130-150 degrees. Due to alkaline oxidation, iron is oxidized. But with this method you should not work in a house or apartment, as an unpleasant smell is released during the work.
• acid method. In this case, the work is carried out in acidic solutions using a chemical or electrochemical method. It is important to place the object in the solution for the set time and act in accordance with the instructions.
• Thermal way. Such bluing is considered the oldest and simplest of the existing ones. This technology consists in the need to heat the steel in the open air. The procedure continues until the top layer of metal enters into a chemical reaction with oxygen. The stronger the heat, the darker the part will become.

There are other ways to obtain blued iron. You can choose the most suitable one and do all the work yourself. The main thing is to strictly follow the sequence of actions and use the correct compositions for bluing.

Alkaline

To burnish metal in this way, it is necessary to perform a clear sequence of actions. First of all, you will have to degrease the surface with a solvent. Then do the following:

1. Take a bowl and pour 100 ml of water into it.
2. It is necessary to dissolve 120 grams of caustic soda and 30 grams of sodium nitrate in it, stirring them until a homogeneous mass.
3. Heat the composition to a temperature of 130-150 degrees.
4. Place the part in the boiling mixture so that it does not come into contact with the walls.
5. The part will turn black after 20 minutes, after which it is washed in distilled water.

When the product is completely dry, it must be lubricated with machine oil and wiped dry. As a result, the coating becomes smooth and wear-resistant. You do not have to additionally polish the product. These rules allow you to give the surface the desired effect without resorting to complex technology. Remember to use a protective mask and thick gloves.

It is important to carry out work only in a stainless container that is of sufficient size. This can be a problem if you plan to burn a large knife. To avoid color differences, the entire surface of the product must be in solution.

Acid

This option is performed in acidic solutions. In this case, electrochemical or chemical processing technology is used. It is important to clean the rust. For this, ordinary sandpaper is suitable. To increase the cleaning speed in advanced cases, you can use a grinder equipped with a metal brush.

Then use a cleansing composition, which is used as sodium triphosphate, ethanol with kerosene or plain kerosene. The part must be immersed in the solution for 15 minutes. In the end, the product should be washed in running water, wiped well and dried.

While the part dries, it is necessary to prepare a solution for acid bluing. Mix the following ingredients:

• 1 liter of water;
• 2 grams of tannic acid;
• 2 grams of tartaric acid.

The next step is the direct burnishing of the knife. Heat the mixture to 150 degrees. Place the item in the container for 15 minutes. Make sure that the metal surface is completely immersed in the solution. Then rinse it in running water and dip it in boiling water. This allows you to completely clean the surface of the solution.

At the final stage, the process of bluing steel in oil is carried out. In this case, the product is immersed in machine oil for 60 minutes, after which it can be used for its intended purpose.

Important! When using this method, cold bluing is also possible. To do this, use a tool such as rusty varnish.

Thermal

Everything is very simple here. Such bluing is considered the oldest. This technology consists in the need to heat the steel in the open air. The procedure continues until the top layer of metal enters into a chemical reaction with oxygen. The stronger the heat, the darker the part will become.

Applying rusty varnish

This bluing agent is often used to obtain a smooth and even surface. It includes steel shavings, but it can be replaced with cast iron shavings. In this case, financial investments will be minimal. In this case, the workpiece must be placed in a chemical agent. As a result, red or black iron oxide appears. This instruction, as a means for cold bluing, gives a long-lasting and effective result.

To get rid of reddish plaque, use a brush with fairly stiff metal bristles. As a result, only black oxide remains.

To begin with, the metal is subjected machining and degrease. Then the product is placed in a special composition. The bluing agent is prepared in a porcelain container. It is important to work with gloves to protect the skin. The composition is made using hydrochloric acid s. It is poured into a container in a small amount. It mixes with metal filings, nitric acid and iron rust.

The mixture is stirred well until the chemical reaction stops, which is accompanied by the evolution of gas. Water and plain vodka are added to the mixture in equal proportions. At the end, it is left for a certain time until it settles. Then it is drained to remove scales and salts that have precipitated.

When the mixture is ready, the processed metal product is placed in it. It is held until it turns black. After that, it is washed under strong pressure of running water.

On the video: burnishing with rusty varnish.

Use of engine oil

Burning a knife can be done at home with oil. You will need the following:

• 500 ml of machine oil;
• equipment for holding the part, such as special hooks, pliers or pliers;
• metal container for bluing in oil;
• rags or paper napkins;
• gas burner, building hair dryer or gas stove.

How to do the procedure if you have a building hair dryer? To do this, the part is laid out on a non-combustible surface, such as a brick. The hair dryer is then set to high heat. The part is heated to the maximum. Then, with the help of pliers or pliers, it is placed in the bath, completely covering the surface with oil. This will ensure an even color at the end of the procedure. Then the part is placed on a paper towel to absorb the oil.

When processing metal in this way, you can use linseed oil. The procedure stops as soon as the desired color is obtained. The process must be repeated 3 or 4 times. At the end of each cycle, the product becomes darker.

If you decide how to burnish a steel product, this method will not make it black. And the surface will not turn out too strong. This bluing agent is suitable if it is necessary to protect a steel product from rust.

Are you thinking how to bury metal objects yourself? To do this, you can use one of the methods suitable for you. Using professional advice, you will get the perfect color of the metal, and the process itself will take place in a way that is safe for you.

Cold bluing involves the use of a bath or a special container. But it cannot be made of any material. A wooden bath or a galvanized container is optimal.

It is good if the container is additionally equipped with hooks for placing the part in the solution. These elements can be made in the form of curved racks or mounted on the wall. Everything is determined by the height of the sides of the container and the dimensions of the workpiece.

For bluing steel, the container must be properly degreased. An organic-based solvent is best suited for this. It can be acetone, perchlorethylene or B-70 gasoline. The base remains inert with respect to these compositions. But for each type of metal, it is necessary to select the optimal solution. Only with its help you can get the optimal color and maximize the performance of the product.

Even if you are cold bluing, work should be done outdoors or in a well ventilated area. This is due to harmful fumes and a strong chemical smell.

If you are unable to clean the surface well with a brush or abrasive, use etching. For each type of metal there is a tool. If you have a ferrous metal product, the bluing liquid includes 100 grams of nitric, 50 grams of sulfuric and 150 grams of hydrochloric acid per 1 liter of distilled water. The surface is treated for at least 2.5 hours. To give a smooth surface, chemical polishing is used.

Thus, the burnishing of a steel object can be done independently. To do this, it is important to choose the most appropriate processing method and adhere to a clear sequence of actions. As a result, you get a corrosion-resistant surface in a suitable shade.

Metal burnishing is used to give a presentable appearance and protection against rust. At home, this procedure is quite simple to perform if you know the basic ways to do it.

Using bluing at home is a profitable procedure that allows you to save the family budget. In this case, a special composition is applied to the metal, which allows blackening and forming a protective film.

First, the steel is cleaned and degreased, then the surface is treated in the chosen way.

Safety regulations:

• All work is done with gloves;
• The bluing solution contains various kinds of chemicals, so it should be stored in original packaging, beware of spilling the substance;
• Nearby should be funds from burns, in case of need to provide first aid;
• Work is carried out in a well-ventilated area;
• It is better not to use metal utensils when working.

You will also need sandpaper. It is used for cleaning surfaces. The metal is usually degreased with acetone, perchlorethylene, B-70 gasoline and other organic solvents. Its surface is inert to these substances (immune).

Metal processing methods

Metal blackening occurs in the following ways: alkaline, acid and thermal. Such work can be carried out on an ax, weapons and other metal products.

Alkaline bluing

The most popular method of blackening steel is chemical oxidation with an alkaline composition. The result obtained is quite high-quality and persistent when the technology is strictly adhered to. The method is based on the ability of the metal to oxidize. Work is performed at 135-150 degrees, while you should be prepared for a characteristic smell.

Blackening in an alkaline way is best done outside the apartment. You can do this in the yard or garage, in a room with good ventilation.

So, let's begin. The first step is to degrease and clean the surface of the metal object well. Remember that bluing at home is impossible without preparing a good alkaline composition.

You can do this in the following way:

1. Pour 100 ml of ordinary water into a porcelain dish.
2. Add 100 g of technical soda and 30 g of sodium nitrate.
3. Stir thoroughly and heat the resulting composition to 135-150 degrees.

The solution is ready, now you need to lower the product that you plan to burn into it for half an hour. Then the metal is washed with distilled water, dried and lubricated evenly with machine oil.

As a result of alkaline bluing at home, a bright black color with a blue tint should appear. To obtain a thicker oxide film, the percentage of alkali in the solution should be increased.

On the video: do-it-yourself alkaline bluing.

Acid bluing

Before bluing, clean the product well with sandpaper. Then you can degrease it by dipping it in kerosene or sodium triphosphate for 10-20 minutes. After that, the part is dried, and at this time you can prepare a solution for blackening.

It is prepared as follows:

1. In 1 liter of water, 2 grams of tartaric and tannic acid are added.
2. The ingredients are thoroughly mixed.
3. The solution is heated to 140-150 degrees.

The part should be lowered into the heated composition for 14-17 minutes, then rinsed with ordinary or boiling water (for better cleaning from the solution).

The last stage is the immersion of the product for 60 minutes in engine oil. Then it needs to be wiped, dried and can be used.

Thermal bluing

This option appeared before everyone else, so it is simpler than others in execution, but no less effective. The method is based on heating metal products until the reaction of oxygen with the metal itself. The intensity of heating varies depending on the desired result.

The table shows the resulting color at different temperature conditions.

To implement the heat treatment, you will need machine oil (500 ml), a bath for machine oil, pliers, a gas hair dryer and dry wipes. Heat treatment should be done on a brick or other non-combustible surface.

Progress:

1. The hair dryer must be turned on at the maximum temperature and the product should be held over it.
2. The heated part is completely immersed in oil, while holding it with pliers.
3. Take out and blot the product with a napkin.
4. Repeat 3 more times the whole procedure from the very beginning.

This method will not give the metal a black color. Blackening with this method is necessary to prevent rust, decorative bluing is rarely done this way.

Oxidation with citric acid

Blackening with citric acid protects against corrosion, oxide films and rust. This is the old way, suitable for high carbon steel. If the knife is oxidized in this way, then in the places where it will be sharpened, the entire coating will come off. It is not too resistant, suitable for items that are rarely used.

For this you will need:

• a pack of citric acid;
• hot water (90-95 degrees);
• machine oil.

In a container from of stainless steel or glass, you need to pour out the whole bag of citric acid (20 g), pour hot water (about 200 g) and mix thoroughly. Dip the product in the prepared composition and leave for 50 minutes. After some time, you can observe the beginning of the reaction. Bubbles will actively form around the part. They can prevent the access of air to the product, so you can periodically (every 10-15 minutes) move the knife so that they disappear from the surface.

After 50 minutes, you can get the part, it will become black at the end of the process. It must be rinsed, oiled and wiped.

blue steel

Hot bluing most often helps to achieve a blue color. This happens when heated for a longer time. Initially, the surface acquires white, yellow, purple hues, and as a result, a beautiful blue color is obtained.

Recipe 1

Burning steel at home in this way assumes the presence of a forge, ideally with automatic blowing. Birch charcoal should be placed in a metal box, leaving room for the metal to be processed.

This design is placed in a hearth, preheated. The metal is smeared with vinegar, rubbed and put in a box when the coal begins to smolder. If a bluish color occurs, the part must be pulled out, cooled slightly and returned to its place. Such manipulations should be done 3-4 times until the correct shade is obtained.

Recipe 2

This method of obtaining blue color is carried out without heat treatment. It will take 3 grams of hexacyanoferrate ("red salt" among the people) and one and a half chlorine iron. Chemical components for safety reasons should be added to water, but not vice versa.

These substances are highly soluble and are strong oxidizing agents. We add them separately to 0.5 l of water, stir and mix into one substance. We dip the steel into the resulting solution until it acquires the desired color.

Noble gray and black colors

A beautiful gray color can be obtained using nitric copper (a type of salt) and denatured alcohol (a type of alcohol). At the same time, a sufficiently powerful film is formed that is well resistant to rust. Salt (70 g) should be melted over a fire, add denatured alcohol (20 g) to it and grease the metal with this mixture, heating it until the correct shade is obtained.

You can blacken stainless steel with different oils (linseed, animal) or wax. They lubricate the object and heat it on fire. As a result, it becomes a noble black color and a stable protective film appears.