Galvanic Corrosion in Pipelines

Date 03-26-2007 04:27

Good Morning ta all
I trust that everyone had a good weekend, unlike us in the Middle east that has Fridays off.

To get back to the subject matter. I would appreciate any information on the galvanic corrosion between the rootpass consumable (pipe ID) and the base metal for sour service pipeline or any other application that some have encountered it.

Specific questions:
- will galvanic corrosion be more severe in a stagnant medium or in a flowing medium?
- if it is too much cathodic towards the basemetal, would corrosion occur in the HAZ region/ adjacent to the weld bead.
- what would be a threshold potential differnce to minimze corrosion either way.
- how representative is the data obtained in a lab test make up medium compared to real life application.

if you have any personal experiense or have previously come accros this topic, please share your insights.

Thanks
So Much to do, so little Time

By js55

Date 03-26-2007 13:33

I'll take a stab at a couple of the general questions. Galvanic attack and all corrosive repsonses are extremely service and material specific. You cannot use a standardized ASTM test to calculate definitively what your gal/cor repsonse will be. Especially considering that the standard ASTM tests are performed ina short time frame that may or may not extrapolate properly to a long term service. You can however use them as a 'rule of thumb' or 'ranking' reference to estimate. Services such as these are miscalculated everyday, and alloys often upgraded. The only way you can know for sure is to perform tests on the exact medium, materials, cycling, temperature, etc. for your service in question.

By Eutectic (**)

Date 03-27-2007 04:10

Good Morning Jeff,

Thanks, it confirms my own thoughts on the subject, GC interaction remains a mystery even in the purest forms.
P.S. Ill still get back to you on the Pulsed subject. just need to get my ducks in a row.

Cheers