Black stains after pickling and passivation.
Black stains after pickling and passivation.
(OP)
Hello all,
One of our contractors is constructing a 316 vessel for us. After pickling and passivation i went over for an inspection and saw some black marks on 1 or 2 welds.
The QC-manager told us these were due to over-pickling and will not have any detrimental effect on the vessel.
That last statement i'm not so sure of. I'm not an expert, but according to what i can find these marks must mean there are still some contaminents or oxides left over in the weld and these should be removed.
Or am i completely wrong?
Kind Regards
Marc
One of our contractors is constructing a 316 vessel for us. After pickling and passivation i went over for an inspection and saw some black marks on 1 or 2 welds.
The QC-manager told us these were due to over-pickling and will not have any detrimental effect on the vessel.
That last statement i'm not so sure of. I'm not an expert, but according to what i can find these marks must mean there are still some contaminents or oxides left over in the weld and these should be removed.
Or am i completely wrong?
Kind Regards
Marc





RE: Black stains after pickling and passivation.
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RE: Black stains after pickling and passivation.
RE: Black stains after pickling and passivation.
Or it could be an area that is very rough/porous from over pickling and it looks black because the texture is different.
Most times you would see a fabricator touch these up with a hand held flap wheel and then spot pickle/passivate to 'fix' them.
Visual variations often draw attention, but they are rarely significant in terms of performance.
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