Why does the color of stainless bolts (nuts, washers, etc.) differ from batch to batch? Are they all made of the same steel?

What colors of stainless steel are there?

Despite the ubiquity of plastics, in our time the scope of metals has not decreased. They are widely used in all types of industry, construction and the manufacture of household appliances. The main disadvantage of all metals - susceptibility to corrosion is often solved by coating metal surfaces with various compounds that reduce the effects of moisture and aggressive agents. However, there are metals that acquire anti-corrosion properties already at the stage of their production.

Stainless steel signs

Types of metals

Such materials include some non-ferrous and, especially, precious metals. However, if gold or platinum really have increased resistance to environmental influences, then less noble metals such as aluminum or copper and their alloys are susceptible to corrosion, it’s just not very noticeable to the naked eye. In addition to being susceptible to corrosion, these metals are expensive and generally not very durable. Another thing is iron. The most durable type of iron, steel, acquires its properties due to the carbon present in its composition.

But steel, despite its high strength and low toughness, is destroyed when exposed to moisture and air. This problem was solved at the beginning of the last century after the discovery of a method for producing stainless steel. This method involves adding the required amount of chromium to the melt. The resulting material not only has high strength and anti-corrosion properties, but also a pleasant light color with a silver tint. The typical stainless steel color in the photo is shown using the example of a refrigerator.

Application

Stainless steel is well known to the average consumer from household appliances, where it has found its wide application. Refrigerators, washing machines, electric and gas stoves, and heating appliances are made from it. At the same time, manufacturers often use such properties of stainless steel as heat resistance - the resistance of steel to corrosion when exposed to high temperatures and aggressive environments and heat resistance - maintaining mechanical strength at high temperatures.

At the same time, manufacturers are faced with the problem of monotonous color design. This problem is solved through the widespread use of a phenomenon called tarnishing - the appearance of an oxide film on the surface of the metal, protecting the stainless steel from corrosion. As a result of the interference of light waves, the surface acquires different colors. The color change of stainless steel occurs depending on the thickness of this film. Stainless steel can be given many different colors through heating. The main colors of tarnish are blue, purple, green, and gold. All these colors have a silvery tint, which gives the equipment a more noble appearance.

Painting with liquid paints

Since this method is best suited for independent use, we will dwell on it in more detail. Automotive paint is best suited for this process. In this case, it is best to add hardeners to it, which should speed up the setting process as much as possible.

As an alternative, you can go through the range of modern paint and varnish manufacturers, choosing those types that are suitable for painting steel surfaces. Moreover, such paints and varnishes are often sold together with a primer composition, which will help increase the adhesion of the coating to the surface.

Color spectrum

By using new electrochemical technologies, metallurgists, in addition to the primary colors, have learned to impart the following colors to stainless steel:

• bronze - widely used in the production of gas stoves;
• red - the usual color of a stainless steel refrigerator has become commonplace, while a stylish red stainless steel refrigerator will decorate any kitchen;
• gold - found application in the manufacture of heaters;
• black - black stainless steel is used in the manufacture of gas and electric stoves and electric kettles.

Additionally, by using different color coatings, you can not only significantly expand the color gamut, but also give the same color different shades.

PROPERTIES AND CHARACTERISTICS OF STAINLESS STEEL

How to define stainless steel ? Stainless steel gained its relevance due to a number of positive properties:

• Resistance to aggressive environmental influences;
• High wear resistance, due to which the service life of the products is more than ten years;
• Thermal resistance to sudden temperature changes;
• High level of resistance to corrosion and other types of destruction;
• Environmental Safety;
• Aesthetically attractive appearance;
• Easy to use and maintain.

Speaking about what stainless steel is and how to define stainless steel , we can say that it is the result of a successful mixture of steel and impurities that enhance its properties. Such impurities are the main component that prevents the formation of rust and premature aging of products. The more impurities, the longer the service life of the steel in general.

The main additional components are:

Colors of metal products: “metallic” and “pearl”

Pearlescent and metallic colors are included in a separate group. They create decorative coatings that imitate metal with a ground, polished or textured texture. Such paints are mainly made glossy. However, it is possible to produce dyes with any percentage of haze.

Pearlescent and metallic shades are created using a special structure:

• Almost all of them consist of two components - a binder base and a coloring spark pigment.
• During the application process, the paint is fixed on the product with a binder base, while the pigment is responsible for shine and color, evenly painting the surface over the entire thickness of the coating.

The appearance of the coating depends on:

• Colors of pigment particles and type of binder.
• The size of the pigment particles. As a result, the coating may look like metal or have a translucent surface with fairly large sparks of metal.
• The way the pigment sparks are oriented in the binder base.

With the help of pearlescent and metallic paints, the decorative properties of products are significantly enhanced. Among the negative qualities of such coatings, one can note: a higher cost compared to analogues, including production costs and complex application, and the need for frequent maintenance.

TYPES OF STAINLESS STEEL

Based on the percentage composition of the main additives, it is customary to distinguish stainless steel from the following types:

Austenitic steels. They contain at least 20% chromium and 4.5% nickel.

Duplex steels. Their chromium content reaches 25%, 1.5% nickel and a slight admixture of nitrogen.

Ferritic steels. Up to 29% chromium is allowed in their composition.

Martensitic steels. Their chromium content is insignificant, no more than 13%, and nickel maximum 4%.

Multicomponent steels. Minimal amounts of chromium and nickel and include a wide range of other enhancing impurities.

Chrome is the main component that simplifies cold deformation, increases the service life of products, and gives an attractive appearance.

Despite the presence of a sufficient number of nuances, questions often arise: how to identify stainless steel, how to distinguish stainless steel from ordinary metal, and how to test stainless steel for quality components . To carry out a distinctive test in everyday conditions, when it is not possible to conduct a serious hardware examination, improvised means are used.

How to distinguish stainless steel from metal?

We invite you to familiarize yourself with methods for determining the type of material composition that are available for use at home and do not require additional equipment or the creation of special conditions.

1. Evaluation of interaction with a magnet

The magnet is a 100% stainless steel identifier. The composition of stainless steel allows it to be magnetized under the influence of Futko currents. Under standard conditions, magnetization of the material does not occur.

1. Saline test

The definition of stainless steel is a product or material that is resistant to corrosion. The technique is budget-friendly. To reproduce it, it is necessary to prepare a concentrated saline solution to place the product in it. If the metal becomes covered with rust within 24 hours, then it is not stainless steel.

This will require the use of a needle file. After a cross-section of the product with tools, the inside of the cut will open in front of the master or user. If it shows signs of yellowness, then it is brass.

1. Determining distinctive characteristics with sandpaper

To identify the metal, it is necessary to remove the surface layer of the product and clean it with copper sulfate. In stainless steel, the surface layer does not change its original characteristics, which cannot be said about metal.

1. Recognition by appearance

Comparison of metals can be carried out by experienced specialists. A professional knows the nuances of changes in the surface and inner layers when exposed to certain elements. During long-term use, sockeye salmon or stainless steel does not experience detachments or tears and retains its original visual characteristics for a long time. The metal fades over time, and the value of the product is reduced to a minimum.

1. Determination of the composition and type of metal based on traces of processing

A microscope and the professionalism of a specialist will tell you how to distinguish metal from stainless steel. Experience using a microscope will help you identify traces of material processing and recognize its qualitative composition.

1. Accurate determination of the difference between sockeye salmon and metal

This can be done with knowledge of physical laws. To do this, it is not necessary to study at institutes; minimal school knowledge is enough. Remember that when you place a body in a glass filled with water, a certain amount of liquid is pushed out. Knowing the mass of the material and the volume of spilled water allows you to find out the mass of the product. By comparing it with the tabular data, you can determine whether it is metal or stainless steel.

1. Product recognition by markings

HOW TO IDENTIFY STAINLESS STEEL: 13 WAYS

Identifying stainless steel using a magnet

Stainless steel does not allow magnetization due to the action of Futko currents. But this technique does not always give the correct result, since iron and martensitic alloys have magnetic properties, and therefore, using a magnet, it is possible to reliably determine only austenitic-iron alloys, which contain a high percentage of nickel and chromium. In other words, it is impossible to 100% identify stainless steel with a magnet, but you can recognize its subtype.

Saline solution

The essence of the method of determining stainless steel with a saline solution is to identify susceptibility to corrosion. A strong saline solution serves as a good provocateur of corrosive destruction. For this purpose, the product to be checked is immersed in a saline solution for a day. Stainless steel, having a high degree of resistance to such aggressive environments, will remain undamaged by corrosion.

Slice method

An incision is made using improvised means. The color of the cut will help distinguish stainless steel from brass, which is similar in color. In the case of the latter, the cut will have a yellow tint. While stainless steel will remain light gray.

Determination of stainless steel with copper sulfate

The top layer is sanded using sandpaper. After which the surface of the stainless steel is treated with a solution of copper sulfate. In this case, the definition of stainless steel, as in the case of the above methods, the stainless steel will not change its external characteristics.

Physical method for determining stainless steel

How to check stainless steel physically?

The method is based on knowledge of the law on the volume of displaced fluid. Stainless steel placed in a container of water will displace a different amount of water than the metal can displace. To do this, you need to know the mass of the product, the mass of the displaced liquid, and have a table of weight differences on hand.

Marking

The marking indicates the properties characteristic of a given material. Based on these properties, you can understand how to identify and distinguish stainless steel from ordinary metal.

Blank Slate Method

Stainless steel does not leave marks from tight contact, while aluminum will give noticeable gray stripes.

Thermal conductivity

For aluminum, unlike stainless steel, it is much higher. In this regard, water in an aluminum container will boil much faster.

Aggressive environments.

When in contact with alkaline and acidic environments, the surface of stainless steel will remain unchanged. Spots will appear on the surface of the aluminum.

Reaction with nitric acid

A few drops of acid reacting with any carbon steel will cause the formation of corrosive fumes. Stainless steel will not react even if the surface is damaged.

Light ebb

The surface of stainless steel gives a yellowish-blue tint.

A mixture of hydrogen peroxide and 20% sulfide

Such a mixture applied to a cut will cause significant darkening visible to the eye if a non-ferrous metal has interacted with the reagent.

Hole

Drilling a hole will help distinguish stainless steel from duralumin by the appearance of the chips.

Identifying stainless steel using a spark

To conduct such a test to determine stainless steel, you need to start the process of grinding the material with a grinder, and sparks and flashes, as mentioned above, will provide the necessary information.

Some tips for choosing paint colors for metal products

Concluding our review, let us dwell on the choice of color for metal products from the RAL catalog. Basically, it depends on the preferences of the customer himself. However, it is worth listening to the recommendations of a specialist:

1. In the table of combinations, you should pay attention to white color and all light colors (beige, milky or lemon yellow), they “work” perfectly in rooms. At the same time, they must be used carefully outside. In the sun, white glares unpleasantly, and the cost of keeping the coating clean will be quite noticeable.
2. Red, yellow and orange are warm colors. Despite the fact that they are less easily soiled than white ones, they are still quite difficult to care for. They will look great on the northern and western sides of the facade, as well as indoors.
3. Green, blue, brown, cherry colors are universal. These shades are included in standard color sets, which makes it possible to save money and ultimately make the design cheaper. In addition, they fit perfectly into modern everyday life.
4. Gray tones look good in a restrained interior design. But more often they are used in manufacturing enterprises. Painting large rooms with a gray color requires adjustment in the direction of lightening, since they may become excessively gloomy. Facades made in light gray tones must be “diluted” with warm colors.

STAINLESS STEEL MARKINGS

There are five types of basic markings:

• 08Х18Н10. Dishes made from such material are allowed for use in the food industry. However, exposure to caustic soda is not allowed.
• 08Х13. One of the most popular grades of steel, most often used in the manufacture of kitchen utensils. Such dishes can be heated to almost any temperature, and can also be stored in refrigerators and freezers.
• 20Х13-40Х13. This steel is used to make sinks and dishes. It copes well with temperature changes, is plastic and resistant to mechanical damage.
• 12X13. Steel products with this marking are used in the wine and alcohol industries.
• 08Х17. This steel has the highest heat resistance and good thermal conductivity. Pans made from this type of stainless steel are in high demand.

STAINLESS STEEL QUALITY ASSESSMENT

Evaluation of the quality characteristics of stainless steel depends on various parameters, such as the amount of additives, joining method, etc. After welding at the seams, stainless steel loses its resistance to corrosion, which can lead to the formation of rust and then to its destruction. Painted stainless steel will need to be cleaned of rust and re-polished, which will cause the steel to lose its resistance to moisture. To evaluate stainless steel in advance, you need to resort to a salt solution: if the material is of high quality, there will be no stains on the steel.

Preparing stainless steel for work

The quality of the final result directly depends on this stage, so it should be carried out as responsibly as possible. The process consists of several stages:

• We study the surface. The surface to be painted must be carefully examined for unevenness or defects. If they are not very large, then it is better to abandon the idea of ​​leveling. The thing is that a perfectly smooth and polished steel surface adheres extremely poorly to paint, and the quality of its painting will be mediocre;
• We give the surface roughness. If the same wood is polished before painting, then with steel everything is different - we must make it matte and slightly rough to the touch. The easiest way to do this is to use a wire brush, but this treatment is only suitable for relatively small surfaces. If the area is large, then it is better to automate the process using a grinding attachment with an abrasive disk of medium grain size. This stage is especially important when processing a surface polished to a shine;
• Cleaning from dirt and dust. After the process of giving the surface a rough appearance, the latter must be cleaned of dust. A simple cloth soaked in water is ideal for this. Try to go over the entire surface, as there should be no loose fragments left on it. For the same reason, work should not be done in a dusty room;
• Degreasing. Grease stains, which may even be invisible to you, greatly reduce the adhesion of paint to the surface. Therefore, the latter must be treated with special acid- or alkaline-based compounds. A popular method is to use an ammonia composition. At the same time, we must not forget about protecting the respiratory tract with a respirator and ventilating the room. Finally, you can use a four percent solution of simple soda, available in every home.

Important! It is necessary to work on painting only after the surface is completely dry.

RESULT: HOW TO IDENTIFY STAINLESS STEEL

Thus, the task of how to identify and distinguish stainless steel from any other types of metals and steels seems quite possible even without the use of serious industrial expert measures. It is enough to remember and apply at least some of the above methods, which provide completely objective information on the distinctive features. If doubts remain, it is better to turn to expert data. Especially when it comes to medical or food products. By the way, many people are also tormented by the question: is it possible to weld stainless steel to ferrous metal? In this article we will break everything down.

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