This standard specifies the specific requirements for chromate conversion coatings used for corrosion protection on electroplated zinc and electroplated cadmium layers. This standard applies to surface finishing that only provides special colors or improves paint adhesion. GB 9800-1988 Chromate conversion coatings for electroplated zinc and electroplated cadmium layers GB9800-1988 standard download decompression password: www.bzxz.net
This standard specifies the specific requirements for chromate conversion coatings used for corrosion protection on electroplated zinc and electroplated cadmium layers. This standard applies to surface finishing that only provides special colors or improves paint adhesion.

UDC 621.794: 669.587 + 669.738A29
National Standard of the People's Republic of China
GB9800—88
Chromate conversion coatings onelectroplated zinc and cadmium coatingsPublished on 1988-09-05
Implemented on 1989-09-01
State Bureau of Technical Supervision
National Standard of the People's Republic of China
Chromate conversion coatings onelectroplated zinc and cadmium coatingsUDC 621.794:669
.587+669.738
GB 9800-88
This standard is equivalent to the international standard ISO4520-81 "Chromate conversion coating on electroplated zinc and electroplated cadmium layers". 1 Subject content and scope of application
This standard specifies the specific requirements for chromate conversion coatings used for corrosion protection on electroplated zinc and electroplated cadmium layers. This standard does not apply to surface finishing that only provides special colors or improves the adhesion strength of paint. 2 Reference standards
GB6458 Neutral salt spray test for metal coatings (NSS test) GB9791 Test method for chromate conversion coating on zinc and cadmium GB9792 Determination of the mass of the film per unit area of ​​conversion coating on metal materials Gravimetric method 3 Film formation method
After electroplating zinc or electroplating cadmium, it is usually immersed in a chromate solution to form a chromate conversion film. The chromate solution is acidic and contains hexavalent chromium salts and other salts that can improve the appearance, hardness and corrosion resistance of the film. The color, type and performance of chromate conversion film are determined by the composition of the solution, but are also affected by pH, temperature, treatment time and coating quality. Electroplated zinc or electroplated cadmium layers form thick, highly corrosion-resistant rainbow or dark-hued chromate conversion films and thin, less corrosion-resistant, bright, clear chromate conversion films in appropriate solutions. Electroplated zinc layers can also obtain bright, clear films by bleaching the colored film in alkaline solutions, phosphoric acid or chromic acid solutions. It is difficult for electroplaters to ensure that chromate conversion films with accurate tones are provided. If accurate tones are required, bleached chromate films can be dyed, but the corrosion resistance is only similar to that of bleached conversion films. When rainbow and dark chromate conversion films are rinsed for the last time, in order to prevent the dissolution of hexavalent chromium, the hot water temperature should not be higher than 60°C, and the rinsing time should be as short as possible.
To prevent the film from dehydrating and cracking, the drying temperature should not exceed 60°C. If dehydrogenation treatment is required, it should be carried out before the formation of chromate conversion film. 4 Grading
4.1 Chromate conversion coatings can be divided into two grades according to their protective properties (each grade includes two types), and their main characteristics are shown in Table 1. Table 1 Grading Characteristics of Chromate Conversion Coatings
D Dark
Typical Appearance
Bright, clear, sometimes with a light blue hue Clear, slightly iridescent
Iridescent
Grass green, olive green, brown, black\ etc. Quality of film layer per unit area
Protection
Limited protection, such as anti-pollution and slight corrosion during transportation and use Good protection against high humidity under conditions such as in the atmosphere, including certain organic atmospheres
Note: 1) Black chromate conversion coatings have different protective properties due to different film-forming processes, and the quality of the film per unit area may also be different. Approved by the State Bureau of Technical Supervision on September 5, 1988, and implemented on September 1, 1989
GB 9800-88
4.2 Expression of the characteristics of chromate conversion coatings: The characteristics of chromate conversion coatings can be expressed by classification alone or by classification and type code. For example:
Fe/Zn 25c
In the above example: Fe
25, 8
5Requirements
2D, Fe/Cd 8c 2
-Base metal (steel or iron)
Represent the electroplating layer (galvanized, plated),
Represent the thickness of the electroplated zinc and electroplated layer, μm, chromate conversion coating,
Classification of chromate conversion coatings:
Type code of chromate conversion coatings.
5.1 General requirements: The conversion film is easy to scratch when it is just formed, and it ages and hardens as it gradually dehydrates. Therefore, care must be taken when handling it within 24 hours after the film is formed, and any performance test should be carried out after 24 hours. 5.2 The adhesion strength of type C and type D chromate conversion films shall be tested in accordance with the provisions of GB9791 and meet the requirements for adhesion strength.
5.3 The mass of the film layer per unit area shall be determined in accordance with the method specified in GB9792. 5.4 Corrosion resistance: When tested in accordance with the provisions of GB6458, the time for the appearance of white corrosion products on each level of chromate conversion film shall not be less than the values ​​listed in Table 2. wwW.bzxz.Net
Table 2 Corrosion resistance requirements for chromate conversion films
Type code
Note: 1) See Chapter 4.
The shortest time for the appearance of white magic corrosion products, h6
5.5The presence of type A and type B chromate conversion films, the presence and content of hexavalent chromium in various types of chromate conversion films, the total chromium content per unit area and other items shall be inspected according to the methods specified in GB9791. 2
Additional remarks:
GB9800—88
This standard was proposed by the Ministry of Machinery and Electronics Industry of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Standardization of Metallic and Non-metallic Coatings. This standard was drafted by the Wuhan Institute of Materials Protection. The main drafter of this standard is Cheng Jin.
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