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Q&As since 1989


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Stains on stainless steel after alkaline cleaning

I am having a staining issues on a 301 stainless steel part , after a 160 degree hot alkaline cleaning , then a cold water rinse , then a citric passivation bath and then three rinses, help help help. It is driving me crazy.

Jodi Keane
- Waterbury , Connecticut
2006

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Please check the water quality ? Suggest use DM water.

Regards,

Jayshree Menon
- Mumbai, India
2006

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Check for oil contamination.

Khair Shishani
aircraft maintenance - Al Ain, UAE
2006

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First of two simultaneous responses --

Dear Jodi
Join the club. This is a problem every passivator has to face. Do you not see parts getting stained as soon as you dry them. How do you dry them? Is it compressed air. Consider drying them by using some fine wood powder ( if the parts are small enough and you can blow off the remaining wood powder from the grooves).
Using DI water can also help as suggested in the first response. Also make sure the pH of your rinses after passivation is as close to neutral as possible.
Hope it helps,

Hemant Kumar
- Florida, USA
2006

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Second of two simultaneous responses --

You may not be rinsing well enough after the hot cleaner. Try coming out of that rinse into the third passivation rinse and then go into the passivation. It is worth a try. If it works, improve your hot cleaner rinse.

James Watts
- Navarre, Florida
2006