Not all stainless steel parts and components are used for industry sensitive or even industry specific applications. However, a great many of these parts that are going to go through the passivation process will be used in electronics in the medical, electronic, telecommunication and aerospace industries where corrosion resistance and adherence to approved standards will be essential.
Most stainless steel passivation for these exacting types of applications will fall under ASTM A967 standards. These standards were actually based on the QQ-P-35C standards required by the United States Department of Defense requirements, although there are slight variations between the two.
The Importance of Standards
One of the most important considerations with the use of standards, including the ASTM A967 standard, is that the end-users can be assured of the specific type of passivation process used to treat the stainless steel.
As all parts also have to be tested after passivation to the specifics of the standard, there is a built-in quality control and verification factor that is not possible through other types of passivation processes not based on a standard. Company A offering passivation to these standards will produce an end product that is identical in quality to Company B, providing both are using the standards and the testing to the requirements.
Within the standards as developed by the American Society for Testing and Materials, which is now an internationally recognized and used set of standards, there are specifications for all aspects of the passivation process and the testing.
The specifics of the standards do not change. However there is a difference between the use of nitric acid and citric acid. In addition, with the citric acid solution, there are three specific treatment options that are used with the 4-10% citric acid solution composition. This includes different temperature and times based, and all may be acceptable providing the final component is able to pass all of the testing requirements.
The testing requirements for the ASTM A967 standard include the humidity and water immersion test, a salt spray test and a copper sulphate test. In some applications, there may also be a requirement for a potassium ferricyanide-nitric acid test. This last test is considered to be the most sensitive to free iron and is often used in specific types of applications such as aerospace and where any free iron present is a concern.
At ProPlate, we utilize ASTM A967 standards and create custom finishing solutions for your stainless steel components. To learn more visit us online at www.proplate.com.
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