This method is applicable to the evaluation of the corrosion resistance of metal coatings and chemically treated layers after atmospheric exposure tests, salt spray tests, corrosion paste tests, and industrial gas tests (such as sulfur dioxide gas, etc.). SJ 1284-1977 Evaluation method for corrosion test results of metal coatings SJ1284-1977 standard download decompression password: www.bzxz.net
This method is applicable to the evaluation of the corrosion resistance of metal coatings and chemically treated layers after atmospheric exposure tests, salt spray tests, corrosion paste tests, and industrial gas tests (such as sulfur dioxide gas, etc.).

Standard of the Fourth Machinery Industry Department of the People's Republic of China
Method for determining the results of corrosion tests on metal coatings SJ1284-77
This method is applicable to the evaluation of the corrosion resistance of metal coatings and chemically treated layers after various corrosion results produced by atmospheric exposure tests, salt tests, corrosion paste tests or industrial gas tests (such as sulfur dioxide gas, etc.). If the main surface area of ​​individual parts is less than 25mm, this method cannot be used for rating.
I. Definition
1. Corrosion point: refers to the penetration of the coating at the corrosion site, directly reaching the base metal, and the corrosion products of the base metal are visible, or due to the corrosion of the base metal, the coating can be partially or completely bulged or lifted up,
cause the coating to discolor or other surface appearance damage. However, if it does not penetrate to the base, it will not be counted as a corrosion point when making a protective rating.
The size of the corrosion point refers to the size of the area where the coating is penetrated, not the size of the area of ​​rust that is produced.
2. Crack: The continuous part of the corrosion point is a crack. 3. Main surface: refers to the coating surface of the main part that plays an important role in the appearance or performance of the product.
If necessary, the main surface should be determined through consultation, or marked on the product process drawing, or a sample with appropriate markings should be submitted. 3. The most
4. The main part used to evaluate the quality of the coating should have a surface area of ​​more than 5000mm2. If the main surface area of ​​individual products is less than 5000mm2, a sufficient number of products should be taken to make the total area of ​​the main surface equal to or greater than 5000mm2. 5. If the grade number to be evaluated is equal to or greater than grade 8, the area of ​​the main surface taken should be greater than 10000mm2
3. Cleaning of samples after the test
6. After the corrosion test, the sample should be inspected immediately. If necessary, the residue of the corrosive medium should be removed. It can be rinsed with running water and then inspected. In some cases, the corrosion products need to be removed to facilitate accurate observation of the corrosion points. This can be done by physical methods, such as scrubbing with wet cotton, but be careful not to damage the coating. IV. Corrosion rate calculation and corrosion resistance rating
7. Corrosion rate calculation: Use a transparent plexiglass plate or plastic film with squares (5mm×5mm) to cover the main surface of the coating to be tested, then the main surface of the coating is divided into a number of squares. Count the total number of squares, assuming it is N. After the coating has been subjected to the corrosion test, corrosion spots appear in some parts. Count the number of squares with corrosion spots, assuming it is five, then:
Corrosion rate (%) = 100
8. Corrosion resistance rating: The corrosion resistance rating is made according to the corrosion rate through the table below. From the numbers in the table, it can be seen that the higher the corrosion rate (%) value, the smaller the rating number, indicating that the corrosion resistance is worse. Conversely, the lower the corrosion rate (%) value, the larger the rating number, indicating that the corrosion resistance is better. The relationship between corrosion rate and rating numbers is shown in the following table: Corrosion
0 (no corrosion point)
0 or more~0.25
0.25 or more~0.5
0.5 or more~1
1 or more~2
2 or more~4
4 or more~8
8 or more~16
16 or more~32
32 or more~64
64 or above
Rating number
Add 9876
Total 3 pages Page 3
SJ1284-77
V. Rating instructions
9. Edge area: When calculating N, if the square located at the edge of the test covers more than half of the test area, it is calculated as one square. If it is less than half of the square, it can be ignored.
10. Corrosion points and cracks across grids: For corrosion points across grids, when calculating n, they are only counted once. If it is a crack, if it extends to more than one square, all the squares where the crack extends should be calculated. Www.bzxZ.net
11. Degradation: If the surface area of ​​the tested specimen is equal to or greater than 10,000 mm2, the surface area of ​​50 mm×50 mm with the most corrosion points must be found. On this surface area, for every 10 small squares (5 mm×5 mm) containing corrosion points, the rating should be reduced by 1 level.
12. No rating:
(1) If 10 or more corrosion points are contained in any two adjacent small squares (5 mm×5 mm), or the area of ​​any corrosion point is greater than 2.5 mm2, the specimen cannot be rated.
(2) If a long crack passes through more than one small square (5 mm×5 mm) and its area exceeds 2.5 mm2 in any square, the specimen cannot be rated. (3) If the specimen includes more than one part and the corrosion degree of these products is extremely obvious after the corrosion test, the specimen cannot be rated. 3
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