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topic 0034

Can high pH corrode SST?

A discussion started in 1995.
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I was given the task to aid in degreasing some flexible metal conduit that was supposed to be stainless steel. Upon immersing the conduit in LPS Precision Clean (4:1 dilution w/ water) for 1/2 hour, I noticed that the bright finish on the conduit had turned to a dull grey in many places. Since I do not know the actual material of the conduit (yet), can anybody tell me if pH 12 solutions have this sort of effect on stainless steel? FYI, LPS Precision Clean contains the following per the MSDS - Tetrapotassium Pyrophosphate, Sodium Metasilicate, and Dipropylene Glycol Methyl Ether along w/ some unspecified surfactants.

Jeff Albom
- El Granada, California

Corrosion Resistance of Stainless Steels
from Abe Books



High pH solutions are reported to dissolve the chromium in SST, and you'll find references to this in the plating handbooks; but on the other hand I have seen SST successfully used as the material of construction for heating coils and tanks for very high pH soak cleaning stations.

So, based on book knowledge, a high pH solution can corrode stainless steel. But based on the experience of years, nah, I don't think that conduit is series 300 SST--maybe aluminum or galvanized steel.

Sorry that I didn't really have any answers for you. But I'd love to hear them when you find them.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

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