Corrosion

[MemphisDepay]

Hello guys,

This is a atmospheric vent piping line that connects from a PRV.There is a clamp aroung the pipe to hold the tag.When I first saw I thought that the pipe/clamp are severly corroded. But when I looked closely it was coating damage with slight corrosion. What does this seem tou you. Is this crevice corrosion?

http://files.engineering.com/getfil...b4b2-4d50-894b-7b6146c28c80&file=DSCN0634.JPG

http://files.engineering.com/getfil...f31c-4fbf-b97f-19416a6030fa&file=DSCN0635.JPG

http://files.engineering.com/getfil...4817-4946-825d-ec89b4e981b0&file=DSCN0649.JPG

http://files.engineering.com/getfil...7272-4804-a47c-1c3aca66c5f4&file=DSCN0637.JPG

http://files.engineering.com/getfil...4f1b-456f-9c36-be679c82f611&file=DSCN0657.JPG

 

[SJones]

At first sight, according to the definition of ASTM G193, yes it is. However, the tag band would seem to be stainless steel, thus you might also wish to investigate the terms "galvanic corrosion," or "bimetallic corrosion."

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[tnatale]

Yes, you have crevice corrosion. The crevice is formed between the band and the pipeline. If you do a Google search on pipeline crevice corrosion support you'll see a lot of examples. The more typical example would be carbon steel on both sides, (you have CS and SS combo). While the SS is corrosion resistant, it will form the crevice and once the corrosion starts, the galvanic issues will play a role.

 

[EdStainless]

Once you remove the band and carefully clean the area you will have a better idea.
As of right now it looks like there is corrosion of the pipe, but is it galvanic from coating damage and contact with SS, or is it simply from the coating damage, or is it related to the crevices formed either from the coating damage or the band....
In any case you need to remove, lightly clean, and inspect.
And then come up with a solution (there are many options out there).

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P.E. Metallurgy, Plymouth Tube