What is the current standard for passivation of stainless steel?

What is the current standard for passivation of stainless steel? At present, the international standards for stainless steel passivation are: American ASTM-A967；; ; China steel pressure vessel GBl50- 1998. Salt spray test is divided into neutral salt spray test (NSS), acetic acid salt spray test (ASS), copper salt accelerated acetic acid salt spray test (CASS) and alternating salt spray test. The main salt spray test standard is QQ-P-35B. Neutral salt spray test (NSS test) is the earliest accelerated corrosion test method with the widest application field. It uses 5% sodium chloride salt solution, and adjusts the PH value of the solution to the neutral range (6 ~ 7) as the spray solution. The test temperature is 35℃, and the salt spray sedimentation rate is required to be between1~ 2ml/2000px2.h. The acetic acid salt spray test (ASS test) is developed on the basis of neutral salt spray test. It is to add some glacial acetic acid to 5% sodium chloride solution, so that the PH value of the solution is reduced to about 3, and the solution becomes acidic, and finally the salt spray formed becomes acidic from neutral salt spray. Its corrosion rate is about 3 times faster than NSS test. Copper salt accelerated acetic acid salt spray test (CASS test) is a rapid salt spray corrosion test recently developed abroad. The test temperature is 50℃, and a small amount of copper salt-copper chloride is added to the salt solution, which strongly induces corrosion. Its corrosion rate is about 8 times that of NSS test. (Alternating salt spray test is a comprehensive salt spray test, which is actually a neutral salt spray test plus a constant moist heat test. Mainly used for cavity-type complete machine products. Through the infiltration of humid environment, salt spray corrosion occurs not only on the surface of the product, but also inside the product. It is to replace the product alternately under the conditions of salt spray and hot and humid environment, and finally check whether the electrical and mechanical properties of the whole machine have changed. Copper sulfate test method and blue dot method can be used for detection. Copper sulfate test is mainly used to test the corrosion resistance of passive film, and blue dot test is used to test whether the passive film is complete.