Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Rinsing after stainless steel passivation
Q. 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
2005
A. 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 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
2005
Passivation rinse tank temperature
Q. Hello,
I have a question, it may seem silly but here goes. I changed my passivation (nitric and H2O) tank to ambient temperature, can I do the same with the rinse? I have been running the rinse at 140 °F as required when I was running my passivation tank at high temperature with sodium dichromate, but I would like to now turn off the heat.
Any responses would be appreciated.
- Rincon, Georgia USA
March 25, 2014
A. Micheline,
I don't see why not. The passivation standards focus much more on the temperature of the acid bath than for the rinse stages. The cleanliness of the rinse water is far more important than its temperature.
Ray Kremer
Stellar Solutions, Inc.
McHenry, Illinois
April 2, 2014
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