Blued steel what is it

Features of metal bluing at home

After rough processing, metal blanks are subjected to various surface processes to improve the quality of the finished product. These include metal bluing. This is a special chemical or thermal process that is carried out to improve the corrosion resistance of a product.

What is bluing?

Steel bluing is a treatment during which steel is coated with an oxide film. In this case, the product is exposed to chemical or thermal effects. The thickness of the surface coating with an oxide layer can reach 10 mm.

Burnishing is considered an effective method of combating rusty metal and the spread of corrosion. If the stages of the selected bluing technology are carried out correctly, complete elimination of rust can be achieved. Burnishing is applied to those blanks that will not be painted in the future.

At the same time, the process of increasing corrosion resistance and changing the appearance does not in any way affect other parameters of metal products. When carrying out processing, the features of bluing should be taken into account:

• observe safety precautions;
• adhere to the specified temperature regime for heating the workpiece;
• When working, use utensils made of galvanized metal.

This way you can protect the body from harmful fumes and increase the effectiveness of your actions.

Bluening methods

Various steel bluing technologies are used in production. Surface treatment is carried out using purchased chemical compounds or improvised means. It is important to know the stages of the work so as not to damage the metal workpiece.

Alkaline

The alkaline method can be used at home. The process consists of several main stages:

1. Degrease the surface to be treated.
2. Prepare a stainless steel container with 100 ml of clean water.
3. Pour 30 grams of sodium nitrate and 120 grams of caustic soda into the liquid. Mix the ingredients thoroughly with water.
4. Slowly heat the mixture to 130°.
5. Transfer the workpiece to the chemical composition.

When the surface of the product takes on a dark shade, you need to remove it from the chemical and wipe it with distilled water. The last step is to lubricate the workpiece with machine oil.

When carrying out work, it is strictly forbidden to change the amount of chemicals used. Otherwise, the metal surface may be damaged. When the product is in a container with a solution, you need to control that it touches each of its sides. There will be stains in the empty spaces.

Acid

When using this method of bluing metal, you need to use an acid solution. Processing process:

1. Remove debris, dirt, paint, and rust from the surface of the workpiece.
2. Immerse the workpiece in a metal basin with clean kerosene. There it should be kept for 25–30 minutes. After cleaning, rinse the workpiece in clean water. Dry in a ventilated area.
3. Make a composition for bluing. To do this, mix 2 grams of tartaric acid, 2 grams of tannic acid and a liter of clean water. Mix the ingredients thoroughly and heat slowly to 150 degrees.
4. Dip the workpiece in the chemical composition and leave for 15 minutes.
5. Wash the product with distilled water and immerse it in a container with machine oil for 60 minutes.

Thermal

This is one of the oldest methods of coating metal surfaces with an oxide film. Thermal bluing is performed outdoors. The workpiece heats up slowly. Heating must be stopped at the moment when the top metal layer reacts with oxygen. As a result, an oxide film should form.

Means for bluing metals

To easily carry out the processing procedure, you can choose ready-made products for bluing metals. They are applied to the surface to be treated using a brush. The further process of work depends on what composition was purchased.

Oil coating

Oil bluing is considered one of the simplest methods of processing metal surfaces. Work process:

1. Clean the part from dirt, paint, and rust. Degrease and dry the surface.
2. Coat the surface with oil. It is applied with a brush.
3. Transfer the workpiece to the muffle furnace and heat to 350 degrees.

You need to remove the product after obtaining the desired shade. Olive, gun and machine oil are suitable for the technological process.

Use of saltpeter

To change the color of a metal product, you can use saltpeter. To do this, you need to purchase ready-made liquid at a hardware store and boil the product in it for 60 minutes.

Means "Clover"

You can bury the metal using the purchased product “Clover”. Initially, the surfaces of the workpiece are cleaned of dirt, rust, and paint. Treated with sandpaper. The product is applied in an even layer to the product. After a certain period of time, a white solution should appear, which must be removed. If the effect is insufficient, the procedure is repeated.

Blueing metal at home

Blueing of metal at home can be done in two ways: cold or hot. In the first option, purchased solutions are used, which are applied to the surface of the workpiece with a brush. After obtaining the desired shade, the chemicals are washed off with soapy water. Burnishing steel in oil is a cold method.

When using hot metal processing, the chemical solution must be selected especially carefully. It can degrade the strength of the material. Experts recommend using alkaline compounds. They do not have a detrimental effect on steel surfaces. When hot processing, the temperature cannot be increased quickly.

The optimal temperature is 100 degrees Celsius. Treatment takes on average about 45 minutes. It is important to use bluing containers made of galvanized metal. The room must be equipped with a good ventilation system. A person must use safety glasses, a respirator, gloves, and overalls.

Source: https://metalloy.ru/obrabotka/zashhita/voronenie-metalla

What means and methods exist for bluing metal yourself?

To ensure that the product can serve for a long time without painting, metal bluing is used at home to protect against corrosion. This processing method creates a thin oxide film on the surface of the parts. It does not allow moisture (H₂O) and gases (CO and O₂) to pass through to the open metal (in real conditions, a chemical reaction occurs to reduce the carbon content with a decrease in hardness).

Oxidation proceeds in such a way that iron exhibits divalent properties. Oxides form on the surface or a layer of insoluble salts forms. Only in the presence of strong acids can the resulting film be dissolved.

Causes of metal corrosion in the open air

The combined action of water and oxygen occurs according to the scheme where both aggressive substances act on pure iron: 4Fe + 6H₂O + 4O₂ = 4Fe(OH)₃.

As a result, iron hydroxide Fe(OH)₃ is formed; it has a red (orange) color and has a loose structure.

Carbon steel, when periodically heated in the environment, loses carbon, and the iron it contains is more susceptible to corrosion. Decarbonization of steel products occurs through the following chemical reactions:

• Fe₃C + CO₂ = 3Fe + 2CO;
• Fe₃C + H₂O = 3Fe + H₂ + CO;
• Fe₃C + 2H₂ = 3Fe + CH₄,

where Fe₃C is cementite, one of the important components of steel. It is this connection that determines the strength and hardness of steel products.

The surface layer contains more pure iron. It is susceptible to water and surrounding gases. The process is growing. Loose rust quickly spreads inside parts.

To prevent corrosion and decarburization, products are coated with paints or primers. Chemical exposure is reduced hundreds of times. But it is not always possible to use liquid or powder paints. A whole group of steel parts is operated without painting:

1. Cold steel and firearms.
2. Products obtained as a result of cold forging.
3. Claiming couples working with gases and liquids.

For them you need to use a different method of protection.

What does steel blueing do?

Some inexperienced craftsmen often do not know what metal bluing is. This method of processing is used quite rarely, believing that it is a rather complicated procedure. In fact, any manufacturer can achieve positive results with his own hands with minimal costs of materials and labor.

During chemical or thermal bluing, an oxide film with a thickness of 13 to 1015 microns is formed on the surface of the steel. The thickness of the resulting layer largely depends on the technology used. When performing this operation, the main goals are achieved:

• the steel product's corrosion resistance increases;
• parts that have been processed are able to remain resistant to aggressive environmental influences.

If there is action of alkalis, acids and special heat treatment, then the surface is covered with oxide,

2Fe + O₂ = 2FeO.

Oxidation, when iron exhibits diatomic properties, forms black films. Depending on their thickness, the color of the product also changes. If there is a sufficiently thick film (up to 1215 microns), then the surface is black. To damage such a coating, you need to apply quite a significant amount of force.

How to oxidize metals at home?

In practice, bluing is performed according to various schemes:

1. Heat treatment of parts followed by oil coating.
2. Heating to boiling temperatures in chemical solutions.
3. Painting with special compounds that penetrate the surface layer. Diffusion of the coating layer with the base occurs.

At home, you can implement any of the methods, you just need to familiarize yourself with the features of the technology, as well as prepare the necessary equipment.

Selection of technology for bluing parts

To choose the right bluing method, it is advisable to decide on a number of specific parameters and recommendations:

• In the case of restoration of damaged coating, the extent of existing damage should be determined. If you need to revive limited areas where there are scratches or small abrasions, the choice is made on the alkaline method of producing an oxide film on the metal surface.
• If the surface of the part is significantly damaged and there is corrosion on it, the existing coating will have to be completely removed.
• Each product has a certain value. Based on this, it is worth estimating how long subsequent operation is expected. If the item will spend most of its time on the wall as an exhibit, simple chemical processing methods are possible.
• For products actively used on hikes or in the open air (knives, utensils or firearms), thermal methods using oil are used.
• When performing work to order, much depends on the price that the customer can pay. Cheap orders are carried out using simple methods, expensive ones involve the use of more expensive bluing techniques. When performing work for third-party customers, the question is: “How much does it cost?” – will be very relevant.
• At the training stage you will have to pay for everything yourself. Any professional training is expensive, but self-learning the basics of the profession has the advantage: knowledge is acquired without additional payment to the mentor.

All that remains is to study the basic methods of applying an oxide film, and then practice the techniques through real experience and gain the necessary skills.

When carrying out bluing work using chemicals, you will have to use tools to clean the surface from dirt and various types of grease. You can do the work manually or use a power tool. The work must be done on a desktop (workbench or cover the table in the apartment with a removable tabletop). In the room itself you need to have equipment and certain protective items:

1. You need a working container for bluing. It should ensure that the part is completely immersed in the solution.
2. Create good exhaust ventilation and fresh air flow. It is advisable to install a probe above the place where processes are carried out, then harmful fumes will not affect humans.
3. When working, you need a container made of material that is neutral to alkalis and acids. It should contain water or a solution that can quickly neutralize the drugs used. The container is made of plastic, glass, porcelain or earthenware.
4. The work must be done with gloves. Here you will need rubber and other types of gloves to prevent solutions from getting on your hands. They must also protect against possible thermal effects.
5. Respiratory protection is achieved by using respirators. When using strong acids, activated carbon filters will be needed.
6. Vision protection is achieved by using safety glasses. There are special glasses for working with chemical reagents; they are sold in work clothing stores.
7. Aprons and jackets made of tarpaulin will protect the body from drops of solutions.

Alkaline steel bluing

The simplest way to apply an oxide film to products is alkaline bluing. The operating principle is based on the use of caustic soda and sodium nitrate (used as a fertilizer). Both components have a pronounced alkaline reaction.

To process a part weighing about 900-1000 g you need to have:

• 100 g caustic soda (NaOH);
• 30 g of sodium nitrate (sodium nitrate NaNO₃).

Process:

1. Dissolve the components in 100 ml of water. If this amount of working solution is not enough, then increase the amount of liquid, as well as caustic soda and nitrate in proportion.
2. The solution is heated to 135145 ⁰С (salt solutions boil at a temperature higher than pure water boils).
3. The part is washed with soap or weak alkali to remove possible greasy stains.
4. Place in the working solution for 30-35 minutes and maintain a high temperature. In a hot state, the rate of film formation on the surface of a steel object will be high.
5. After completing the procedure, it is necessary to wash off the remaining working solution.
6. Wipe the product with vegetable or technical oil.
7. Then thoroughly wipe the item with a rag; only a thin layer of oil film will remain, which will further protect the finished product.

As a result, the metal surface will receive a black coating with a bluish tint. It is quite durable and can withstand minor mechanical stress.

Other alkaline treatments are possible in NaOH and KOH solutions. Prepare a solution in which 300-400 g of each component is dissolved. The minimum concentration of alkalis is 700 g per 1 liter of solution.

The processing procedure takes place according to the technology described above. In this case, the result is a film with slightly more blue.

Attention! During alkaline processing, the liquid level should be maintained so that the part is always completely in the solution. Then the entire coating will be uniform.

Before starting acid coating, the workpiece is cleaned and washed. You can get by with pure alcohol or a 40% strength solution (regular vodka). Some people use white spirit. Using a swab, clean the surface from greasy stains.

Recipe No. 1

Working solution for bluing:

• 2 g citric acid;
• 2 g oxalic acid;
• 1 liter of water.

Process:

1. The solution is heated to a temperature of 120-125 ⁰C.
2. Place the product in it for 20 minutes.
3. Once completed, the part is removed and washed with a slightly alkaline solution. You can use a sponge soaked in shampoo.
4. The treatment is completed by rubbing with machine oil.

The product takes on a black color with some brown tint.

Recipe No. 2

Vegetable tannins (tannins) are used. They are obtained from oak or willow branches.

Preparation of concentrate:

• willow or oak branches (about 3 kg) are boiled in a 10 liter container;
• 3 hours after cooking, a black solution forms;
• the branches are removed from the solution;
• evaporate the solution to 3 liters. The result is concentrated tannic acid. Only part of the solution is used for bluing. The remainder of the concentrate is poured into a glass container and closed with a tight lid (can be stored for up to 34 years).

Blued parts:

1. 2030 g of tanning concentrate is used per 1 liter of working solution.
2. To activate the process, bluing is carried out with citric acid, which is added to the working solution (23 g per 1 liter of water).
3. The part that needs to be blued is placed in the prepared solution.
4. The duration of the process is 24..30 hours.
5. After processing, the part is removed and washed.
6. The finished part is wiped with machine oil.
7. Remove any remaining oil from the part using a rag.

Using "Rusty Varnish"

“Rusty varnish” is on sale. It is used for surface coating of parts:

• the part is wiped clean from residual grease;
• varnished;
• use an acetone-based solvent, for example, No. 646, to wash off excess varnish from the surface;
• This is one of the fastest bluing methods using ready-made solutions.

bluing at home.

Thermal bluing of parts

In industrial conditions, they prefer to perform bluing using a thermal method. Usually this operation is combined with low tempering, which relieves internal stresses inside steel products:

1. The part is heated in a muffle furnace for 20-30 minutes to a temperature of 180-220 ⁰C.
2. The removed part is wiped with machine oil using a swab. It is advisable to treat all surfaces.
3. If necessary, the treatments are repeated.
4. Usually, a double heat treatment is sufficient to obtain a high-quality blued surface.

Information: weapons factories producing firearms and bladed weapons use thermal bluing. The coating on many products lasts more than 100 years. Example, Mosin rifles manufactured in 1891 and Nagan revolvers released at the end of 1888.

Source: https://metmastanki.ru/voronenie-metalla-v-domashnih-usloviyah-sposoby

Popular methods for bluing steel at home

Steel bluing is increasingly used for painting metal products. It provides reliable surface protection from rust and a decorative finish. With the chemical dyeing option, a protective shell appears on the surface. Oils and acids are used during the work process. Depending on the type of material used and the degree of heating, metal compounds acquire a natural shade.

Many people believe that this processing option is used only in factory conditions. But you can organize it yourself if you follow the sequence of actions and use suitable means.

What can you achieve with bluing?

As a result of this work, a film of iron oxide will appear on the surface. The dimensions of its thickness completely depend on the technology used. It can be 1-10 micrometers. Using the metal bluing 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 obtain the required coverage in many ways. But the most popular of them are alkaline, thermal or acid bluing. Alkaline treatment is ideal for DIY 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.

For work, use only stainless steel utensils. Steel bluing is carried out under a certain temperature regime. The solution is kept in a boiling state, which is why you need to work with it extremely carefully.

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

Important! After completion of processing, metal products must be thoroughly washed in a soapy solution.

Popular bluing methods

Blueing technology includes several methods, the main ones being the following:

• Alkaline method. In this case, you will have to work with oxidizing agents at a temperature of 130-150 degrees. Thanks to alkaline oxidation, iron is oxidized. But you should not work with this method in a house or apartment, as an unpleasant odor is released during the work.
• Acid method. In this case, the work is performed in acidic solutions using a chemical or electrochemical method. It is important to place the item in the solution for the specified time and act in accordance with the instructions.
• Thermal method. This type of bluing is considered the oldest and simplest in existence. This technology involves heating steel in the open air. The procedure continues until the top layer of metal reacts chemically with oxygen. The higher 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 bluing compounds.

Alkaline

To blue metal using this method, you must follow 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 smooth.
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 will 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 burnish a large knife. To avoid color changes, the entire surface of the product must be in the solution.

Acid

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

Then use a cleaning composition such as sodium triphosphate, ethyl alcohol with kerosene, or simple kerosene. The part must be immersed in the solution for 15 minutes. Finally, the product should be rinsed in running water, wiped well and dried.

While the part is drying, 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.

At the next stage, the knife is directly blued. 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 under running water and plunge it into boiling water. This allows you to completely clean the surface of the solution.

At the final stage, the process of bluing the 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 product such as rusty varnish.

Thermal

Everything is very simple here. This bluing is considered the oldest. This technology involves heating steel in the open air. The procedure continues until the top layer of metal reacts chemically with oxygen. The higher the heat, the darker the part will become.

Application of rust varnish

This bluing agent is often used to obtain a smooth and even surface. It contains steel shavings, but they 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. The result is red or black iron oxide. This instruction, as a means for cold bluing, gives a long-lasting and effective result.

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

First, the metal is machined and degreased. Then the product is placed in a special composition. The bluing agent is prepared in a porcelain container. It is important to wear gloves to protect your skin. The composition is made using hydrochloric acid. It is poured in a small amount into a container. It is mixed with metal filings, nitric acid and iron rust.

The mixture is stirred well until the chemical reaction, which is accompanied by the release of gas, stops. Add water and regular vodka to the mixture in equal proportions. Finally, it is left for a certain time until it settles. Then it is drained to remove scale and salts that have precipitated.

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

Source: https://GidPoKraske.ru/spetsialnye-materialy/obrabotka-metallicheskih-predmetov/voronenie-stali.html

Blueing

Steel products tend to release a thin coating when exposed to air, which protects them from the corrosion process. However, the released coating is not able to completely cope with chemical destruction. For this reason, in the field of metallurgy there is the concept of “steel bluing”. It implies the creation of a protective film on the surface of products using artificial methods. There are several known ways of this process:

1. Alkaline;
2. Acid;
3. Thermal.

Today, the bluing procedure is used, rather, to improve the appearance, although previously it was actively used precisely to reduce the risk of corrosion.

Burnishing is a process of chemical-thermal treatment of steels, during which a protective thin film is formed on the surface of the steel . In a simple version, thermal bluing is an oxide film of a metal (for example, iron oxide).

Choosing a bluing method

Since there are several types of procedures, they have their own characteristics, advantages, as well as execution processes. To choose the right type of bluing, you need to pay attention to the following recommendations:

1. First, the level of damage to the original bluing should be analyzed . If, in general, it has practically not been lost, then you can carry out the procedure for updating the coating using alkaline bluing. In the event that the main areas of the coating have suffered from corrosion, you will have to completely get rid of the remnants of the original bluing and use one of the following two types of procedures;
2. Secondly, it is important to consider the lifespan of the steel product . Indeed, depending on the date of their manufacture, one can guess how it was processed.
3. should also be assessed . To do this, you need to compare the cost and value of the product with the costs of its processing. After all, each method differs in the equipment and means used. For example, alkaline bluing is cheaper than thermal bluing.
4. You need to decide on the budget allocated for the procedure. After all, it was previously mentioned that each of the types differs in methodology, and therefore in the funds spent.

Acid bluing

Acid bluing, also called chemical bluing, differs in technique from alkaline bluing. The alkaline method involves treating steel using special dyes, while the chemical method involves the use of substances generated during the oxidation process.

The acid bluing procedure is carried out as follows:

1. First of all, it is necessary to polish the areas of the steel product that will be subjected to the bluing composition. Sandpaper is suitable for this step;
2. Then you will need to prepare a cleaning solution , as well as available means for the cleansing operation. For example, a sieve for immersing small individual parts in a solution;
3. Once all the parts are ready, you can immerse them in the cleaning solution. As already mentioned, this can be kerosene, ethyl alcohol containing kerosene, or sodium triphosphate. Dip the parts into the solution for 15 minutes, after which you need to thoroughly rinse it with cold water and wipe the parts;
4. The most important step in acid bluing is immersing the steel product in the solution . To prepare it, you should mix two grams of two types of acids per liter of water - tannic and tartaric. These components should be heated to approximately 150 degrees and the steel should be left for 15 minutes. Chemical reagents such as “Rusty varnish” or iron(III) chloride are also used;
5. The parts should to remove the bluing solution with cold water;
6. Then you need to dip the steel parts in water brought to a boil. In this way, the remains of the blued solution can be completely eliminated;
7. The final step of acid bluing is immersing the steel parts in oil with water-repellent properties; 50 minutes is enough for this.

Thermal bluing

The oldest method of imparting protective properties and color to iron. Its essence is to heat the product in the open air to a certain temperature at which oxygen in the air enters into a chemical reaction with the surface layer of the product. Depending on the heating temperature and heating time, the greater the depth of the surface layer of the metal the oxidation process occurs. And the darker the dark blue color of this layer becomes.

Table of color dependence on steel annealing temperature in the open air

Colors	Heating temperature
Pale yellow	220°
Pale straw yellow	230°
Golden yellow	246°
Brown-yellow to brown-red	356°
Purple red	265°
Purple	275°
Lilac	280°
Blue	290°
Cornflower	295°
Indigo	300°
Dark blue	310°
Sea water color	320°

Bluening technique

1. Changes in metal color due to temperature

   If desired, you can rid the steel product of its original bluing. To do this, you will need acetic acid or rust removers on automotive parts;

2. Then comes the polishing turn. This step will help repair minor damage such as scratches. In this case, you will need sandpaper;
3. After which the metal parts should be cleaned, which part of the weapon will be subject to bluing.

Thus, if bluing is to be done, then it must be dipped in a special solution. The solution may be based on kerosene, sodium triphosphate, or a mixture of ethyl alcohol and kerosene.

If you plan to clean only the parts, then you must first put them in a sieve, and then dip the sieve in one of the solutions described above;

1. Although alkaline bluing is also called cold bluing, the process involves heating the steel. This step is desirable in order to create a better result.
2. After heating, you need to apply a special solution for bluing the metal, which can be purchased over the counter. They can use the following mixture: 2.5 grams of a pinch of red salt (potassium hexacyanoferrate(III)) with iron sesquichloride per sheet of water. A type of uniform blue color can be obtained as a result.

You will need a brush or applicator, with which you need to evenly distribute the solution over the entire surface of the steel product. It should be taken into account that the parts will be different in size, which means that when processing them, different available tools will be required. Thus, it is better to treat small parts with a cotton swab, and larger parts with a cotton pad. The main thing is to maintain uniformity of distribution;

1. In the next step, the solution must be applied to the product again. This will need to be done until the desired result is noticeable. In this case, for repeated applications, you must use new, clean applicators, cotton swabs or discs.

It should be noted that the depth of the bluing color depends on the number of applications of the solution. In order to get a deep black-blue tint, you will have to use the solution 5-7 times;

1. Once the desired result is achieved, all that remains is to treat the steel with a special oil. It will need to be applied every hour, and the old layer will need to be removed using cotton wool.

Source: http://www.m-deer.ru/tehnologiya/voronenie-stali.html

Burnishing steel at home

Burnishing (otherwise known as oxidation) is the process of coating the surface of steel products with a thin layer of oxides. Burnishing is carried out chemically - using reactions with various substances and thermally - by heating.

Blueing

The goal of the process is to increase the corrosion resistance of products and improve their appearance. Traditionally, bluing was applied to steel weapons - first to cold steel, and then to firearms. Today, steel bluing is widely used in defense and civil engineering, as well as in artistic crafts. The process is also available at home.

What can be achieved by bluing

As a result of chemical or thermal treatment, a layer of iron oxide with a thickness of 1 to 10 microns appears on the surface of a steel part. The thickness of the layer is determined by the selected processing technology.

Blueing of metal allows you to achieve two main goals:

• Increasing the corrosion resistance of the product. Treated parts do not rust.
• Improved appearance. It is especially important for those parts that, due to operating conditions, cannot be painted.

Temperature conditions for bluing

The treatment does not affect other properties of the steel.

Blueing of steel is possible not only in production conditions, but also at home. There are many methods and compositions, almost all of them involve the use of chemically active substances that can cause serious harm to health. To successfully and safely use these substances at home, you must follow the following safety rules:

• Use a protective mask and gloves.
• Ensure ventilation of the room in which work is carried out.
• Use stainless steel utensils.
• Do not exceed the recommended processing temperature.

Methods for bluing metals at home and requirements for their implementation

Popular methods of bluing metal at home are:

• Boiling in self-prepared or purchased chemical compositions.
• Coating the steel with special oil and subsequent heat treatment.
• Coating the surface with the prepared composition at room temperature.

Burnishing steel at home

Chemical bluing of iron also involves preparatory operations of etching and cleaning, as well as grinding and polishing.

When carrying out blueing of steel, it is important to select a container for the solution so that it completely covers the object being treated.

Features of chemical bluing and recipes for some compositions

Before applying a new coating at home, you must remove the old one. This is done by combining mechanical and chemical cleaning methods.

To obtain a durable and beautiful coating, the part must be boiled for 30 to 90 minutes, during which time part of the solution boils away. The workpiece must be completely covered with the composition at all times, so the composition must be prepared with a reserve and periodically topped up during boiling.

At the end of the chemical bluing procedure, the product should be washed in a soapy solution, dried and generously lubricated with oil.

There are many options for chemical bluing. In some, the composition is made by the master himself, while others involve the use of ready-made factory-made products, such as Parisian oxide, Voron3M, Clover and others.

Means for bluing metals

Relatively simple methods of bluing, available for doing it yourself, include surface application of oil, saltpeter and the purchased composition “Clover”

Sapphire for bluing

Oil coating

This is one of the most popular home methods. The technology is divided into the following operations:

• The part is sanded and degreased with a solvent.
• Cover with oil.
• In a muffle furnace it is heated to 350-400 °C. It is permissible to use an oven.
• The cooled part takes on a black or brown tint.
• To saturate the color, the procedure is repeated.

The oil is applied with a brush or by dipping the product into a container of oil. Different types of oil are used, such as

• weapons;
• olive;
• flaxseed

Use of saltpeter

Home craftsmen achieve excellent results using saltpeter solution. You can purchase a ready-made solution, or you can make it yourself:

• water-1000 ml;
• sodium nitrate - 0.5 kg;
• caustic soda - 0.5 kg.

After boiling for an hour, a smooth surface of a deep blue-black color is obtained that does not require further processing.

Means "Clover"

The gel-like product can be purchased in 50 ml jars and is used for alloys with a chromium content of no more than 3 percent

Means "Clover"

It is designed to restore localized corrosion. To obtain a bright shade, the product will have to be applied several times. The product should first be sanded and wiped with a degreaser.

Apply clover with a brush and leave for two minutes. The white-yellow coating that appears is washed off with water and the part is wiped with a rag.

Cold bluing at home

“Clover” does not require heat treatment of the part, so this method is considered cold bluing. Cold bluing can be carried out by other means.

• "Voron-3M". The drug forms a dense film of deep black color on the surface.
• "Paris Oxide" An imported selenium-based preparation is supplied in three containers: 1- for surface preparation, 2- the main composition and 3- a fixative that gives the coating additional protection.

Liquid for cold bluing is applied to the parts with a brush, and after painting it is washed off with warm soapy water. The method is popular for processing barrels and other parts of firearms that do not require boiling.

If you are bluing steel at home, you need to wisely choose the components of the boiling solution. Heating hardened parts can lead to them losing their strength properties.

Alkaline solutions have a less harmful effect on steel, and experienced craftsmen advise choosing them. Treatment with acidic solutions is preferably carried out at low temperatures

So, for example, when using an acid composition for bluing steel from:

• calcium nitrate – 94%;
• orthophosphoric acid – 3%;
• manganese dioxide – 3%.

processing is carried out from half an hour to 45 minutes at 100 ° C

Metal blackening

Depending on the acidity of the environment in which the workpiece is processed, the color of the resulting coating changes, from yellow to black. Therefore, bluing and blackening of metal are not the same thing. The required shade is selected by varying the intensity and duration of heat treatment and the percentage of solution components.

Metal blackening

If you take a mixture of 7 parts copper nitrate and 3 parts alcohol denatured alcohol, apply it to the product and heat it over a fire, then as it heats up the coating begins to change its color. When the desired shade is achieved, stop heating.

It is also possible to blacken steel by coating it with oil and calcining it in an open flame. The result is a durable film of deep black color. There are other compositions for blackening.

Using machine oil

Oil bluing of steel is also available at home.

To carry out the procedure you will need:

• 0.5 liters of oil.
• Equipment for placing the product: hooks, pliers, spacers.
• Stainless steel container.
• A sufficient amount of rags or non-woven napkins.

Source: https://stankiexpert.ru/tehnologii/voronenie-stali.html

Blued steel what is it?

Burnishing (otherwise known as oxidation) is the process of coating the surface of steel products with a thin layer of oxides. Burnishing is carried out chemically - using reactions with various substances and thermally - by heating.

Blueing

The goal of the process is to increase the corrosion resistance of products and improve their appearance. Traditionally, bluing was applied to steel weapons - first to cold steel, and then to firearms. Today, steel bluing is widely used in defense and civil engineering, as well as in artistic crafts. The process is also available at home.

How to make steel blueing at home. In saltpeter, oil, “Clover” agent

Burnishing or oxidation is a method of surface coating (finishing) of metal products in blue, black, blue-black or tarnished colors by exposing them to chemical and thermal methods.

It is used for the purpose of corrosion protection of metal products, and also gives the surface an attractive tint. There are many ways to surface tint metals. The main one is the creation of an oxide film.

The most common are chemical (alkaline and acidic) and thermal effects on the surface. As a result of this treatment, the chemical composition and structure of the surface layer changes. Externally, this is manifested by the formation of a film in the form of metal oxide.

You can carry out the coating yourself using simpler technologies.

Method number 1:

1. Water is poured into a container (porcelain) of the appropriate size and sodium nitrate (sodium nitrate) and caustic soda (sodium hydroxide) are dissolved in it in the ratio: per 100 ml 30 g of sodium and 100 g of soda.
2. The mixture is heated to 140 - 160 ° C, and the workpiece is placed in it, which remains there for at least 30 minutes.

If the process is carried out correctly, the result will be a deep black coating, sometimes with a bluish tint.

Method number 2:

A bluish tint to the film can be obtained using a boiling saturated alkaline solution in which potassium or sodium hydroxide is dissolved in high concentration. At least 700 grams of a chemical substance dissolves in 1 liter of water.

These recipes are provided as an example. There are many other chemical formulations using nitrites and nitrates.

Oxidation in an acidic environment is carried out at lower temperatures. For example, when using an acid solution consisting of:

• calcium nitrate – 30 hours,
• orthophosphoric acid – 1 hour,
• manganese dioxide – 1 tsp.

Oxidation is carried out by keeping the workpiece in the solution for at least 30-45 minutes at 100°C.

Use of saltpeter

A good result of chemical bluing is obtained by a classic solution using saltpeter in addition to those given earlier. As a result of boiling the part in a solution of sodium nitrate at a temperature of 130 - 150 ° C, a durable oxide coating of a shiny black-blue hue is obtained.

Recipe for composition with saltpeter:

• Distilled water – 1 liter;
• Sodium nitrate (NaNO3) – 500 g;
• Caustic soda (NaOH) – 500 g.

Ready-made kits with saltpeter for oxidation are available for sale.

You can watch the process of bluing in saltpeter in the video:

The surface with this treatment looks smooth and does not require additional polishing.

Surface treatment with Clover

You can treat metal surfaces with the ready-made “Clover” product. It has a gel-like consistency and is sold in small 50 ml containers.

It is used for minor corrosion damage to metal. To obtain maximum coloring of the product, you need to treat it with Clover two to three times. Before applying it, the part must be sanded and degreased.

Apply the product with a brush and leave for 2 minutes. If a whitish-yellow coating appears, it should be washed off with warm water and the surface wiped dry with a cloth.

The advantage of this product is its ease of use, which is why it is often used to coat weapons. It has no effect on steel containing more than 3% Cr.

Burnishing steel at home

The question of how to blue steel at home interests many.

Most of the parts that are blued are steel products. Therefore, the methods described above for treating the metal surface by oxidation and coating with an oil film are mainly used for steel alloys.

Many brands of steel are susceptible to rust. The coating for steel products primarily serves as protection against corrosion and at the same time gives them an attractive appearance. The degree of protection and color of the oxide film depends on the thickness of the layer and the reagents used. The thickness can vary from 1 to 10 microns.

When bluing steel products using a chemical method, the choice of solution components when using heating to high temperatures should be approached with caution. For example, there is a ban on such processing of hardened parts, as well as steels that cannot be heated to high temperatures. This can lead to a deterioration in their technological properties.

It is for this reason that when high heat treatment is necessary, it is recommended to use alkaline solutions. They are more gentle.

Oxidation in acidic compounds is carried out at lower temperatures. For example, when using an acid composition consisting of:

• calcium nitrate – 30 hours,
• orthophosphoric acid – 1 hour,
• manganese dioxide – 1 hour,
• oxidation is carried out at a temperature of 100°C, keeping the part in the solution for at least 30-45 minutes.

Blueing of metal and steel at home: types, examples of recipes

Blueing (blackening) of metal or steel is a coating of the surface with a special layer. It gives the product a certain color: black, blue or another. With this treatment, a beautiful tint appears. However, the method is widely used due to its practical benefits: objects coated with a special film are well protected from corrosion. The process has long been widespread in industry. Some people use bluing at home.

There are several ways of such processing . In industry, bluing is carried out by changing the structural composition of the surface. Application - in a special way. At home, using such technologies is very expensive or simply impossible.

However, there are ways to blacken steel at home. This does not require industrial equipment. Everything you need can be found in the store. These methods are presented below.

Hot method

The hot method involves exposure to high temperature . First, the metal is tarred, then burned, for example, with a blowtorch.

The principle is as simple as possible and has been used since ancient times. Even an ordinary kitchen stove is enough for work. Under the influence of temperature, the top layer interacts with oxygen.

Heating should be carried out slowly, gradually increasing to 400 °C. The surface becomes first brown and then black. You will need oil: olive or gun oil. It is important to calculate its amount and not overdo it. Otherwise there will be stains.

The method at home is used less often than others due to technology. Although it has advantages:

• the protective effect lasts longer than with the cold method;
• harmless to health;
• requires low costs.

Before flameless firing, it is advisable to treat the product with a special composition, which includes:

• sulfur;
• grease.

The ratio of components is one to twenty, respectively. Apply as thin a layer as possible. As a result, the protective surface is very smooth.

You can check the quality of bluing in a simple way. Dip the brush into plain water and brush over the treated surface. There should be a film, but not a drop.

Cold way

Another processing method is cold bluing. Often used if products cannot be subjected to heavy loads. It takes a little time and also doesn't require a lot of money.

The idea is to coat the surface with a special solution, for example, Parisian oxide. Typically applied with a brush. For greater effect, the product is immersed in the solution. After the procedure, the product:

1. They wash.
2. Wipe with a rag. It must be moistened with alcohol.

Application of oxidizing agents

There is a method using molten oxidizing agents:

This blackening of metal at home involves immersion in a melt. The product remains in it until the surface acquires a characteristic color . When working, it is worth remembering that the listed substances are hazardous to health. They can be replaced with the following solutions:

• hot salt;
• alkaline.

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.

There are many recipes for bluing. Each master prefers his own , some may have tricks. In ancient times, blued steel recipes were often kept secret. Today you can find various recipes for every taste.

Cold bluing

The following example of cold bluing of a house can be given:

1. Take a liter of water (distilled), two types of acid: 30% hydrochloric (4 g), 69% nitric (13.5 g). Ferric chloride (170 g) and divalent copper sulfate (4 g) are also added.
2. The mixture is treated with the surface and left for some time. The longer the better.
3. Rust is removed using water steam and a brush.
4. Everything is repeated until the result is the desired one. Some do this up to 10-20 times.

Recipe with oxidizing agent

For example, the following recipe for an alkaline solution can be given:

1. You will need caustic soda (400 g), sodium nitrate (10 g), water (600 ml).
2. The mixture should act for 30 minutes or longer.
3. Then the surface is washed well, dried, and slightly oiled. If the alkali is not completely washed off, plaque will form.

Care should be taken during operation. Hot substances and chemicals can cause damage to health or damage property. It is important not to forget about the correct selection of containers, suitable clothing and basic safety precautions.

Source: https://tokar.guru/metally/voronenie-metalla-stali-v-domashnih-usloviyah.html