The surfaces of the springs after shot blasting must be protected from atmospheric influence or exposure to aggressive environments, the surface of the springs is covered with a special layer that protects it from premature destruction.

There are many types of protective coatings. The choice of one type of coating or another depends on the operating conditions of the spring.

Anti-corrosion coatings increase the service life of springs.

The choice of coating must be approached with knowledge of the impact various types coatings on elastic elements.

The protective coating should not lead to deterioration mechanical properties springs

During the galvanizing process, hydrogenation of metals occurs, which sharply reduces ductility and long-term strength, which leads to brittleness of products.

Hydrogenation of metals can occur both during their manufacture during the process of etching, electroplating, and during cathodic polarization. The penetration of hydrogen into a metal leads to changes in the parameters of the crystal lattice, electrochemical and mechanical properties.

When using galvanizing coating, a heating operation is necessarily used for the purpose of dehydration.

Main types of coatings

Galvanizing

Application of zinc by galvanic method to the surface of the spring in layers from 6 (Ts6khr.) to 18 (Ts18khr.) microns. The coating has good adhesion and elasticity. Depending on the passivation it has different shades.

Chemical phosphating (Chem.Phos)

The most common method of protecting anti-corrosion coating. Used for springs when operating in adverse atmospheric conditions. During the coating process, the metal does not become hydrogenated, does not require dehydration, and there is no risk of spring becoming brittle.

The coating is used before applying enamel or primer or as an independent coating - followed by impregnation with chromium (Chem.Phos.hr.), oil (Chem.Phos.pr.)

Chemical oxidation

It is an anti-corrosion coating to protect springs and metal products during long-term storage and during operation in adverse atmospheric conditions.

The coating is used before applying enamel or primer or as an independent coating - followed by impregnation with chromium (Chem.Ox.hr.), oil (Chem.Ox.prm.).

Cadmium plating

Application of cadmium by galvanic method to the surface of the spring in layers from 6 (Kd6xr.) to 18 (Kd 18xr.) microns. The coating has good adhesion and elasticity.
It is used in particularly harsh operating conditions of springs; it has limited use due to high toxicity when coating products. Depending on the passivation it has different shades.

Requires dehydration to eliminate the risk of hydrogen saturation.

Nickel plating

Applying nickel to the surface of the spring in a layer of 6 to 18 microns. Used in particularly harsh operating conditions of springs. Due to the low adhesion to steel, nickel is applied to a copper substrate to increase decorative properties upon completion, a thin (1 µm) layer of chromium (Chem. H24) is applied.

Requires dehydration to eliminate the risk of hydrogen saturation.

Electropolishing

It is an electrochemical process of anodic dissolution of the surface of a product placed in a special electrolyte and connected to the positive pole of a current source.

When current passes through the formed circuit, selective dissolution of the treated surface occurs - surface protrusions, which are the peaks of roughness, are removed.

Electropolishing levels the surface, i.e., removes large protrusions (waviness) and glosses it, eliminating roughness (up to 0.01 microns).

It is used as a method of extra-clean finishing or finishing of the surface to increase its corrosion resistance and improve its appearance.

Suitable for heat-resistant and stainless steels type 12Х18Н10Т, ХН77TYUR.

Paint and varnish coatings

composite compositions applied to surfaces in liquid or powder form in uniform thin layers and, after drying and curing, forming a film that has strong adhesion to the base. The formed film is called a paint coating, the property of which is to protect the surface from external influences (water, corrosion, temperatures, harmful substances), giving it a certain look, color and texture. The required number of layers is indicated in design documentation. Designed primarily for large-sized springs.

Introduction date for newly developed products 01.01.87

for products in production - when revising technical documentation

This standard specifies the designations of metallic and non-metallic inorganic coatings in technical documentation.

1. Designations of base metal processing methods are given in table. 1.

Table 1

2. Designations of methods for obtaining coating are given in table. 2.

Table 2

* The method of producing coatings colored during the anodic oxidation of aluminum and its alloys, magnesium and its alloys, titanium alloys is designated “Anocolor”.

** The method of producing coatings by thermal decomposition of organometallic compounds is designated Mos Tr

Table 2

3. The coating material, consisting of metal, is designated by symbols in the form of one or two letters included in the Russian name of the corresponding metal.

The designations of the coating material, consisting of metal, are given in table. 3.

Table 3

4. Designations of nickel and chrome coatings are given in the mandatory.

5. The coating material, consisting of an alloy, is designated by the symbols of the components included in the alloy, separated by a hyphen, and the maximum mass fraction of the first or second (in the case of a three-component alloy) components in the alloy is indicated in parentheses, separating them with a semicolon. For example, coating with a copper-zinc alloy with a mass fraction of copper 50-60% and zinc 40-50% is designated M-C (60); coating with a copper-tin-lead alloy with a mass fraction of copper 70-78%, tin 10-18%, lead 4-20% is designated M-O-C (78; 18).

In the designation of the alloy coating material, if necessary, it is allowed to indicate the minimum and maximum mass fractions of the components, for example, coating with a gold-nickel alloy with a mass fraction of gold of 93.0-95.0%, nickel of 5.0-7.0% is designated Zl-N ( 93.0-95.0).

When designating the coating of watch and jewelry parts with alloys based on precious metals, it is allowed to indicate the average mass fraction of the components.

For newly developed alloys, the components are designated in order of decreasing their mass fraction.

6. Designations of alloy coatings are given in table. 4.

Table 4

Table 4 (Changed edition, Amendment No. 3).

7. In the designation of the coating material obtained by burning in, indicate the brand of the source material (paste) in accordance with the regulatory and technical documentation.

8. In the designation of solder coating obtained by the hot method, indicate the brand of solder in accordance with GOST 21930-76, GOST 21931-76.

9. Designations of non-metallic inorganic coatings are given in table. 5.

Table 5

10. If it is necessary to indicate the electrolyte (solution) from which the coating is to be obtained, use the designations given in the mandatory appendices.

Electrolytes (solutions) not listed in the appendices are designated by their full name, for example, Ts9. ammonium chloride. xp, M15. pyrophosphate.

11. Designations of the functional properties of coatings are given in table. 6.

Table 6

12. Designations of decorative properties of coatings are given in table. 7.

Table 7

* The color of the coating corresponding to the natural color of the deposited metal (zinc, copper, chromium, gold, etc.) does not serve as a basis for classifying the coating as painted.

The color of the coating is indicated by its full name, with the exception of black coating – part.

13. Designations for additional coating processing are given in table. 8.

Table 8

* If necessary, indicate the color of the chromate film: khaki - khaki, colorless - btsv; rainbow film color – no designation.

14. The designation of additional treatment of the coating by impregnation, hydrophobization, or application of paint and varnish coating may be replaced by the designation of the brand of material used for additional processing.

The grade of material used for additional coating processing is designated in accordance with the regulatory and technical documentation for the material.

The designation of a specific paint coating used as an additional treatment is carried out in accordance with GOST 9.032-74.

15. Methods of production, coating material, designation of electrolyte (solution), properties and color of the coating, additional processing not listed in this standard are indicated according to the technical documentation or written down by the full name.

(Changed edition, Amendment No. 2).

16. The procedure for designating the coating in technical documentation:

designation of the method of processing the base metal (if necessary);

designation of the method of obtaining the coating;

designation of coating material;

minimum coating thickness;

designation of the electrolyte (solution) from which the coating is required (if necessary);

designation of functional or decorative properties of the coating (if necessary);

designation of additional processing (if necessary).

The designation of the coating does not necessarily contain all of the listed components.

If necessary, it is allowed to indicate the minimum and maximum thicknesses separated by a hyphen in the designation of the coating.

It is allowed to indicate the production method, material and thickness of the coating in the designation of the coating, while the remaining components of the designation are indicated in the technical requirements of the drawing.

(Changed edition, Amendment No. 2).

17. Coating thickness equal to or less than 1 micron is not indicated in the designation unless there is a technical need (except for precious metals).

18. Coatings used as technological coatings (for example, zinc during zincate processing of aluminum and its alloys, nickel on corrosion-resistant steel, copper on copper alloys, copper on steel made from cyanide electrolyte before acid copper plating) may not be indicated in the designation.

19. If the coating is subjected to several types of additional processing, they are indicated in technological sequence.

20. The coating designation is recorded on a line. All components of the designation are separated from each other by dots, with the exception of the coating material and thickness, as well as the designation of additional paint coating treatment, which is separated from the designation of a metallic or non-metallic inorganic coating by a fraction line.

The designation of the production method and coating material should be written in capital letters, the remaining components - in lowercase letters.

Examples of recording the designation of coatings are given in.

(Changed edition, Amendment No. 1, 2, 3).

21. The procedure for designating coatings according to international standards is given in.

21. Introduced additionally (Changed edition, Amendment No. 3).

APPENDIX 1

Mandatory

DESIGNATIONS FOR NICKEL AND CHROME COATINGS

* If necessary, the technical requirements of the drawing indicate the symbol chemical element or the formula of the chemical compound used as the substance to be precipitated.

Note . It is allowed to use abbreviations and indicate the total thickness of the coating.

(Changed edition, Amendment No. 2).

APPENDIX 2

Mandatory

DESIGNATIONS OF ELECTROLYTES FOR OBTAINING COATINGS

APPENDIX 3

Mandatory

DESIGNATIONS FOR SOLUTIONS FOR OBTAINING COATINGS

(Changed edition, Amendment No. 1).

APPENDIX 4

Mandatory

EXAMPLES OF RECORDING COATING DESIGNATIONS

APPENDIX 5

Information

DESIGNATION OF COATINGS ACCORDING TO INTERNATIONAL STANDARDS

1. The base metal and coating material is designated by the chemical symbol of the element.

The base metal material, which consists of an alloy, is designated by the chemical symbol of the element with the highest mass fraction. The main non-metallic material is designated NM, plastic – PL.

The coating material, consisting of an alloy, is designated by the chemical symbols of the components included in the alloy, separating them with a hyphen. The maximum mass fraction of the first component is indicated after the chemical symbol of the first component before the hyphen.

2. The designation of methods for obtaining the coating is given in table. 9.

Table 9

3. Designations for additional coating processing are given in table. 10.

Table 10

* The color of the chromate film is indicated by:

A – colorless with a bluish tint; B – colorless with a rainbow tint; C – yellow, rainbow; D – olive (khaki).

Coatings A and B belong to class 1 chromate coatings, coatings C and D , having higher corrosion resistance, belong to class 2.

4. The designation of types of nickel and chromium coatings is given in table. 11.

Table 11

5. The designation is written on the line in the following order:

the chemical symbol for the base metal or the symbol for the nonmetal followed by a slash;

method of coating, in which the chemical symbol of the metal of the sublayer is indicated;

chemical symbol of the coating metal (if necessary, the purity of the metal in percentage is indicated in parentheses);

a figure expressing the minimum coating thickness per work surface in microns;

designation of the type of coating (if necessary);

designation of additional processing and class (if necessary).

Examples of designations are given in table. 12.

Table 12

Appendix 5 Added additionally (Change No. 3).

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Academy of the Lithuanian SSR

DEVELOPERS

E.B. Davidavichus, Ph.D. chem. sciences; G.V. Kozlova, Ph.D. tech. sciences (topic leaders); E.B. Romashkene, Ph.D. chem. sciences; T.I. Berezhnyak; A.I. Volkov, Ph.D. tech. sciences; T.A. Karmanova

2. APPROVED AND ENTERED INTO EFFECT by Resolution of the USSR State Committee on Standards dated January 24, 1985 No. 164

3. The date of the first inspection is 1992; inspection frequency – 5 years

4. Instead of GOST 9.037-77; GOST 21484-76

5. REFERENCE REGULATIVE AND TECHNICAL DOCUMENTS

6. REISSUE with Amendments No. 1, 2, approved in October 1985, February 1987 (IUS 1-86, 5-87)

The word "corrosion" comes from the Latin " corrosio"which means" fret"Corrosion is the physical and chemical process of destruction of materials and products made from them, leading to their deterioration operational properties, under the influence environment. To prevent corrosion, many methods and means have been invented.

You can learn more about corrosion from the film:

Types and Designation of Coatings

There is quite large number coatings applied in various ways on fasteners. All coatings can be divided into three types: protective, protective-decorative, decorative.

On the territory of the republics former USSR, at the moment, the following are accepted symbols types of protective and protective-decorative coatings of fasteners -, etc. (in the drawings and summary tables you can find both letter and numerical designations of the coating) - all the most common types of coatings are shown in the following table:

The name of the coating is placed after the dot, at the end of the designation of the fastener element. The number immediately after the coating designation indicates the thickness of the applied coating in microns, microns (1 micron = 1/1000 mm). If the coating is multilayer, then the total thickness of all layers of the coating is indicated.

How to determine coating parameters in a fastener designation

• Bolt M20-6gx80.58. 019 GOST 7798-70 - Bolt with plated number 01 (zinc, chromated - the most common coating is “galvanic galvanization”; it looks shiny white, sometimes with a yellowish or bluish tint) thickness 9 µm ;
• Nut M14-6N. 0522 GOST 5927-70 - Nut plated number 05 (chemical oxide, impregnated with oil - popularly called “oxidation”; outwardly looks black, shiny or matte) thickness 22 µm ;
• Oil can 1.2. Ts6 GOST 19853-74 - coated grease fitting C (zinc - also “galvanization”, also called “hot zinc” - according to the method of coating; visually differs from “galvanic galvanization” in the absence of pronounced shine and the visible structure of “flakes” on the surface of the coated part) thickness 6 µm ;
• Washer A.24.01.10kp. Kd6.hr GOST 11371-89 - Coated washer Kd.hr (cadmium, with chromating - what is called “cadmium plating”; looks yellow, with a rainbow sheen) thickness 6 microns ;
• Screw V.M5-6gx25.32. 1315 GOST 1491-80 - plated brass screw number 13 (nickel, simply called "nickel plated"; looks grayish-white with a slight shine) thickness 15 µm ;
• Washer 8.BrAMts9-2. M.N.H.b.32 GOST 6402-70 - bronze washer with multi-layer coating M.N.H.b (copper-nickel-chrome coating, or, more simply, “chrome-plated”; looks mirror-like, with a pronounced shine) total thickness 32 µm .

Non-metallic inorganic coatings, consisting of inorganic metal compounds, include chromate, phosphate, oxide and other coatings. The phosphate coating ranges in color from light gray to black.

Phosphate films created on the surface of metal products have a number of properties, including:

1. increased corrosion resistance
2. oil absorption capacity
3. adhesive ability
4. anti-friction properties
5. electrical insulating qualities

The following steels can be subjected to chemical phosphating:

• carbon
• low alloy
• medium alloyed
• cast iron
• magnesium
• aluminum alloys
• cadmium
• zinc coatings, etc.

The essence of chemical phosphating of metals and alloys is their processing in acidified solutions of monophosphates or monosubstituted phosphates of iron, zinc, manganese and others.

In the process of chemical phosphating, hydrolysis of monosubstituted metal phosphates occurs, which creates an equilibrium between phosphoric acid and mono-, di-, tri-substituted metal phosphates, and free phosphoric acid is formed, which interacts with the base metal during the phosphating process, making it difficult to create soluble dibasic and trisubstituted phosphates, which make up the bulk of phosphate films. The type of cations in the phosphating solution has a great influence on the composition of phosphate films. The iron phosphate formed as a result of this process is not oxidized by atmospheric oxygen, and therefore phosphate films have high protective properties. The sizes of crystal structures can be different, it all depends on the preparation of the metal surface. Fine-crystalline films have the highest protective properties. Coarse-crystalline films have the lowest protective properties. The property of phosphate films to increase the adhesion of adhesive, paint and other similar coatings is main reason phosphating applications for fasteners and springs. The high adhesion strength of the phosphate film to the paint coating and increased protective properties are influenced by the structure phosphate coatings. There is a molecular bond between the metal and the phosphate film. Its oil absorption capacity, porosity and antifriction properties depend on the structure of the phosphate film. Additional processing improves the quality of the protective properties of the phosphate film. This treatment is carried out in solutions of chromium compounds, hydrophobization, oiling and painting.

For oiling phosphated parts, aviation or spindle oil heated to 100-110 C is mainly used. It is also used for oiling at room temperature emulsion or solution of oil in organic compounds.

When hydrophobizing, a thin water-repellent (hydrophobic) film is formed on the surface of the parts. Oil absorption refers to the degree to which the phosphate film absorbs oil applied to it. The phosphate film increases oil absorption by approximately two times. The following example one can characterize how the protective properties of an oiled phosphate film increase: if in a corrosion chamber on a non-phosphorized steel spring (spraying a three percent sodium chloride solution) corrosion is detected after 0.1 hour, then on a phosphated and oiled spring after 40-48 hours. If the surface of the base metal has phosphate films accumulated by oil or paraffin, this results in a sharp decrease in the coefficient of friction. When testing unphosphated steel, previously ground, at a stress of 0.047 MPa, setting occurs immediately, while phosphated steel with the same steel, without the use of lubrication, continues to work satisfactorily for 95 minutes. If phosphated steel is lubricated with paraffin, then setting occurs no earlier than fifty hours later. Phosphate films have dielectric properties, which makes it possible to use phosphating to form an electrical insulating coating and use such parts in transformers, generators, etc.
When impregnating phosphate films with bakelite and oil varnishes, the breakdown voltage increases significantly.

For phosphating springs and steel parts of medium and low strength (1400 MPa), the Majef salt solution is most widely used. Manganese and iron monophosphate, called Majef, is used as the starting components for making the solution. The phosphate film formed in the Majef saline solution can have a thickness of 7 to 50 microns. Phosphate films have high adhesion strength to steel, a microporous structure, and good electrical insulating properties (breakdown voltage up to 1000 V). The electrical insulating properties and heat resistance of phosphate films are maintained up to approximately 5000 C. If the phosphate film is heated to 350 C, this leads to the film losing crystallized water, which changes its structure and reduces its protective properties by 2-3 times. When high-strength steels are phosphated in a Majef solution, corrosion cracking appears in places of elastic tensile stress (especially in springs). To prevent such manifestations, zinc phosphate baths are used. For mass phosphating of small parts and fasteners, baths with rotating drums installed in them are used, the same ones are used in galvanic processes.