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Rinsing after stainless steel passivation
What are the minimum requirements of water (pH, hardness, conductivity, etc.) to wash stainless steel after performing any manufacturing process and for passivation purposes?
Sergio Ortizfiltration - Monterrey, Nuevo Leon, Mexico
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Your question is quite broad to be answered in a couple lines, but you are right to be concerned on this matters. Water quality can directly affect the quality of products. The water quality will depend a lot on the application (medical, aerospace, semiconductor, etc).
In the case of citric/nitric passivation, according ASTM
A967 [link is to spec at TechStreet] final rinse water should not exceed total dissolved solids of 200 ppm. I even believe this is too much. I think softened and 10 micron filtered water is ok for general purposes. R.O. is preferred. pH of rinse water must also be controlled to a "neutral" range to avoid product carrying acid residue to the customer.
If the application is critical, such as semiconductor industry, ultrapure deionized (DI) water is a must, as well as monitoring purity of parts. So you can see the application must be considered to know what water class is needed.
High purity Components Manufacturing - Hermosillo, Sonora, Mexico