galvanic corrosion between SS and carbon steel

[andygo11]

Hi, we met an issue that, a new valve with cast body made of A351 CG8M (317SS)is installed on the carbon steel piping. The product in the piping is deaerated river water which means the low oxygen. Do I need a isolation kit for the SS to carbon for this case?

 

[moltenmetal]

Small, inefficient low conductivity cathode coupled to a large anode in this case- personally I wouldn't bother with the isolation kit, but I guess it depends on corrosion allowance in the carbon steel pipe and what else is in that river water, and how long you need it to last.

 

[EdStainless]

The CS pipe near the valve will see some accelerated corrosion, how much depends on both oxygen and conductivity of the water.
If you are expecting very long life (>10yr) then you need to thin about it, either isolation of using much heavier CS pieces adjacent to the valve so that you have more material to loose.

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P.E. Metallurgy, Plymouth Tube

 

[andygo11]

I got a water analysis saying the water may contain about 300 ppb oxygen. Does this cause corrosion issue?

 

[EdStainless]

What is the conductivity?

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P.E. Metallurgy, Plymouth Tube

 

[weldstan]

I would also be concerned with MIC at sealing locations on the SS valve.