Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

Passivation of 316 Stainless - Bath required?

I own a food grade tank washout facility. We washout tanker trucks used to haul dairy, juice, cooking oils, etc. I received a request from a customer to pacify new tanks. My research indicates that citric acid would be the best choice for this. What I am not clear on is whether or not the tank would need to be completely filled with the citric acid solution (10% ratio) or if we could apply it with our current process using a rotating nozzle that provides 360 degree coverage of the tank over a 1 minute time period. The nature of the process would keep a high moisture content inside of the tank, but not provide complete immersion. Would this work?

Brian,
Using a rotating nozzle (or, "spray ball") to provide a washdown of the interior of a large tank with passivation chemistry is a common procedure. However one minute is not enough time. Normally the solution is pumped from the bottom of the tank up through the spray ball again to provide continuous coverage for at least 20 minutes.

Failing this, you would have to either coat the interior with a gel version of the passivation chemical, or fill the tank completely with the standard liquid version.

adv.
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