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Letter 12045
Passivation of 304L Stainless Steel
Welds
I have a question regarding the need to passivate welds on a 304L
tank assembly. this tank will be exposed to a PH of 3-4. My concern
is with the carbon migrating due to the heat of the tig welding. I am
currently looking into a mig process called STT which should help the
heat affected zone. Will passivation protect the surface only and
also, will the PH of the sultion the tank is being exposed to remove
the passivation process.
Bob Young
- Lancaster, PA
Bob:
Any time you weld stainless steel the welds, at least, need to be
passivated if you want them to be corrosion resistant. What you end
up with in the weld and heat zone of the weld are alloys that are
totally different than the base metal.
Once you get the welds passivated, they should withstand the pH of
3-4 with no problem, unless you are talking about bleach, HCl or
other halide containing material. These can do bad things to
stainless and to welds.
pH 3-4 will not destroy the passivation layer unless it is one of
the above materials or similar.
Both nitric acid and our citric acid based formulations give good
results in passivation of the welds. There are pastes available if
the units are too large to dip in tanks. Contact us if we can help.
Dear Reader, please --
- Post a
question on a different subject.
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- Answer or follow-up on this subject (in non-commercial
fashion).
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