Gas line corrosion - Pics

[Joss10]

Dear mates,
Pictures were taken from a pipe sample, it belongs to 4" CS-HP (90 Barg) gas line.
Background and findings : no SRB reported, no corrosion inhibitors injected, water was found inside the line, CO2 contents < 3%.
I'm thinking in Organic acid corrosion produced by APB colony.
Mitigation measure ??
Thanks in advance for any input you can have.

 

[metengr]

Sure does appear to be MIC. It would be beneficial to obtain confirmation of the type of MIC. Can you extract a sample from this location?

 

[SJones]

Try running through the 'Ten Commandments To Prevent MIC In Your System,' R Javaherdashti, Materials Performance, November 2005, pp 46-47. This will help to either firm up or alter the MIC theory. Water and CO2 should really be your first focus.

Steve Jones
Materials & Corrosion Engineer

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

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

 

[Joss10]

Dear Steve,
Thanks for you input about how to prevent MIC.
Two facts to think about MIC : localized corroded area was found in a straight part of the line, so no turbulent flow there and the statement in API 571 here below ( see photos).
API 571 - 4.3.8.5 Appearance or Morphology of Damage
b) Damage is often characterized by cup-shaped pits within pits in carbon steel.
Regards.

 

[SJones]

Indeed, but have you found any bacteria in the system at all? If you look at the NALCO photographic compendium, Corrosion in the petroleum industry, you will also see a picture of CO2 corrosion in tubing, also straight, which is not too dissimilar. In order to control future corrosion, it is necessary to be clear on the degradation mechanisms occurring. For MIC, it should really be a case of rule it in, rather than rule it out. It could well have been MIC from hydrotest water that got exacerbated by CO2 corrosion, but it's no good us sitting at our desks looking at a photograph and trying to recommend a corrosion control solution to you.

Steve Jones
Materials & Corrosion Engineer

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

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

 

[mrfailure]

You should, if you can, contact a MIC lab and get a kit to obtain a sample to send them for analysis. Was this already done? Is this the reason no SRB was identified as being present?

Aaron Tanzer

http://www.lehightesting.com

 

[EdStainless]

Are these location dependent? bottom, sides, top of line?

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Plymouth Tube

 

[Joss10]

Yes, we are looking for SRB and APB, the location of the corroded point is at 6 hours.
Thanks for the inputs.

 

[stanweld]

Is corrosion at low point in the line as well as at the bottom (6:00 position)?

 

[Joss10]

Hi Stanweld, Yes, it is at low point.

 

[stanweld]

I tend to agree with Steve. CO2 corrosion, possibly initiated by MIC from hydrotest water.

 

[Joss10]

Hi Stanweld, this line was never hydrotested, the water is due to the wet gas in any case.

 

[stanweld]

In which case, it's CO2 caused by water condensate from the gas at the point of corrosion.