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Welded Inconel 625 corrosion

Welded Inconel 625 corrosion

(OP)
A newly (few months old) welded 625 spools with matching filler showed corrosion of the weld and the HAZ (couple of inches on both sides of the weld). This happens for all the welded joints on the pipe. The pipe is offshore. I suspect that no pickling and passivation was done for the welds. I cannot trust what the construction company says about their procedure.

Is there any other opinions? How to verify this without destructive testing? and how to repair it?

Regards,
A

RE: Welded Inconel 625 corrosion

Tend to agree. HAZ will not extend 2" beyond the weld but potential for oxide/heat tint will. Also suspect contamination due to improper wire brush cleaning. This assumes that the material and weld metal are correct. It is often preferred to upgrade the chemistry of the filler metal from the base metal equivalent; e.g., E/ERNiCrMo-10.

RE: Welded Inconel 625 corrosion

I agree with Stan on all points.
HAZ is narrow, so surface contamination is likely cause.
What size is the line? What ID inspection was done after welding? Any pictures?
The filler should have been a"C" type alloy (622, 59, 686.
The combination of contaminated tools (steel), poor (or no) ID purge, and no pickle has doomed you.
The only repair is to cut the welds (and 3" on each side) out and do it right.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Welded Inconel 625 corrosion

(OP)
Thanks Stan and Ed,

Unfortunately, I cannot take pics!
The only information we have is that the filler is a matching filler not C type as confirmed by PMI.
The line is 2 inch HC line.
What I can add is that the rust/corrosion can be considered mild and, for some welds, is only on the top half of the line/weld (may be the welder did not even bother to brush the lower half!)
No information about any ID purging/testing of the line after welding is available.

Regards,
A

RE: Welded Inconel 625 corrosion

Of poor purge practice left the weld oxide spotty.
If the corrosion is mild now you could go back and pickle these lines. If you do it before any serious pitting develops you can minimize the long term damage.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

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