SS/CS

[pipesvessels1]

All,

Apologies if this has been covered elsewhere but I could not find it,

I have an ASME VIII A516 Gr70 unlined vessel and have been requested to weld in some 316L internals (baffles, weirs). The internals are not pressure retaining. The internals and their connections are small relative to the large mass of CS. Can I proceed and weld in the internals with suitable electrodes? Is there some method of assessing the 'corrosiveness' and rate of corrosion given the sizes of the available anode and cathodes therefore, calculating a design life?

Cheers,

 

[stanweld]

Stainless steel internals are routinely specified for use in carbon steel vessels by corrosion and process engineers. Unless you have specific knowledge to peclude adherence to the Owner's/Engineer's request, you must comply.

 

[metengr]

Just to add above, make sure you use the correct electrodes for DMW;

E309/ER309 for service temperatures below 800 deg F

Above, use Inco weld A or equivalent.

 

[MJCronin]

pipes....

Corrosion between stainless steel and carbon steel becomes an issue when the carbon steel is electrically connected and in a very small area compared to the stainless.

Carbon steel is, of course the "sacraficial anode" in the couple

This sometimes happens in a fabrication shop when the same brushes/abrasive wheels are used for both materials.

The two materials are not far apart in the galvanic series.

Good luck

-MJC

 

[SJones]

The selection of stainless steel implies that metal loss corrosion for carbon steel is expected. Therefore, some enhanced corrosion of the carbon steel shell is a possibility. Area ratios would be a factor in the risk consideration but the principal assessments would be the expected carbon steel corrosion rate in the process environment and the expected frequency of inspection. If it is a hydrocarbon production process environment, several corrosion prediction tools are available to run assessments.

Steve Jones
Materials & Corrosion Engineer

http://www.oilandgaspeople.com/cv/11499664

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