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304 Discolloration in New tank

304 Discolloration in New tank

304 Discolloration in New tank


Has anyone experienced this sort of corrosion in a new stainless product and what causes it?
Vessel was filled with tap water

RE: 304 Discolloration in New tank

That appears to be oxides that formed at elevated temperatures during heating. There are brush on picking compounds that will remove the discoloration and restore corrosion resistance.

RE: 304 Discolloration in New tank

Yes i agree.
The photo on the left is the door which is sealed by a rubber seal and the right photo is the frame of which the door seals against.
This style of corrosion is occurring all around the tank, even after the parts were acided and polished.
We manufacture 100s of tanks a year and this has never happened before
Is it possible the water it was filled with is contaminated?

RE: 304 Discolloration in New tank

It could have been some minor water contamination, it could have been insufficient cleaning after fabrication and polishing.
It doesn't take much to get this staining on 304.
I suspect that it wasn't pickled well enough after welding, and then it should have been passivated (cleaned to remove residual iron in the surface) after polishing. That either traces of oxide were still embedded in the surface or that the Cr depeated material from just under the scale had not been removed.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: 304 Discolloration in New tank

A mild case of heat tint. Needs to be removed if corrosion is of any concern.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

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