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Salt spray corrosion is a common and most damaging atmospheric corrosion.
The salt spray test is an environmental test that mainly uses the simulated salt spray environmental conditions created by salt spray test equipment to assess the corrosion resistance of a product or metal material. It is divided into two major categories, one for natural environmental exposure tests and the other for accelerated artificial salt spray environmental tests. Artificially simulated salt spray environmental test is to use a test equipment with a certain volume of space - salt spray test chamber, in its volumetric space with artificial methods, resulting in a salt spray environment to assess the product's resistance to salt spray corrosion quality and quality . Compared with the natural environment, the salt concentration of the chloride in the salt spray environment can be several times or several times of that of the normal natural environment, which greatly increases the corrosion rate. The salt spray test is performed on the product and results are obtained. The time has also been greatly shortened.
Artificially simulated salt spray tests include neutral salt spray test, acetate spray test, copper salt accelerated acetate spray test, and alternating salt spray test.
Guideline:
GB/T 2423.17; IEC 60068-2-11; GB/T 10125; ISO 9227; ASTM B 117;
GB.T 2423.18; IEC 60068-2-52; ASTM B 368; MIL-STD-202; EIA-364-26
(1) Neutral Salt Spray Test (NSS Test)
It is the earliest one of the most widely used field of accelerated corrosion test methods. It uses a 5% aqueous solution of sodium chloride, and the pH of the solution is adjusted to a neutral range (6 to 7) as a solution for spraying. The test temperature is taken at 35°C, and the deposition rate of salt spray is required to be between 1 and 2ml/80cm2.h.
(2) Acetate spray test (ASS test)
It was developed on the basis of a neutral salt spray test. It is to add some glacial acetic acid in 5% sodium chloride solution, so that the PH value of the solution is reduced to about 3, the solution becomes acidic, and the final salt fog is also changed from neutral salt fog to acidic. Its corrosion rate is about three times faster than the NSS test.
(3) Copper Salt Accelerated Acetate Spray Test (CASS Test)
It is a rapid salt spray corrosion test recently developed abroad. The test temperature is 50°C. Adding a small amount of copper salt, cupric chloride, into the salt solution strongly induces corrosion. Its corrosion rate is about 8 times that of the NSS test.
(4) Alternating Salt Spray Test
It is an integrated salt spray test that is actually a neutral salt spray test plus a constant damp heat test. It is mainly used for cavity type machine products. Through the infiltration of the tide environment, the salt spray corrosion will not only be produced on the surface of the product, but also produced inside the product. It is to switch the product alternately under the conditions of salt spray and damp heat, and finally to assess whether there is any change in the electrical properties and mechanical properties of the complete product.
Test item: Salt spray test Salt mist Test
Reference standards: IEC60068-2-11 (GB/T2423.17), ISO 4628.3, ASTM B117, JIS-Z2371...
Common test parameters:
Salt fog can be divided into three categories:
Neutral salt spray test (NSS test) (Solution: PH value in the neutral range (6.5 ~ 7.2), the test temperature is taken at 35 °C)
Acetate spray test (ASS test) (solution: add some acetic acid, PH value dropped to 3 or so)
Copper Salt Accelerated Acetate Spray Test (CASS Experiment) (Test Temperature 50 °C, Salt Solution Adding Small Copper Salt - Copper Chloride)
Test time: 16H (minimum)