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Tank Integrity with Respect to Passivation Process

January 4, 2012

Q. We manufacture cleaning equipment and have an application in the field where the customer is using Method 1, Type 2 of AMS2700.

Our passivation tank is constructed with 304 stainless...the wetted surfaces darkened severely after approximately 30 hours of service.

The customer is concerned, as are we.

Is this darkening a self-limiting phenomenon, or are we slowly dissolving the tank?

Is this phenomenon accelerating the consumption of the nitric and/or dichromate?



Thanks for any insight.

Brian Keene
process engineer - Danbury, Connecticut, USA

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March 7, 2012

Hello Brian,

You will get a little staining from the dichromate but please have your customer make very sure that they have grounded it properly. I speak from experience, our electrician did not ground the tank properly and we had the same thing happen.
Tell them to check their iron content. If it is high already then it is definitely eating the tank.

Hope this helps,

Micheline Forth
- Rincon, Georgia, USA