Galvanic Corrosion Between SS-304 Octagonal Ring Gasket and SA350 Gr.LF2 Cl.2 Flange

[mtk-14]

With reference to attached pictures, is is possible to have galvanic corrosion caused by SS-304 Octagonal Ring Gasket and SA350 Gr.LF2 Cl.2 Flange being assembled with water trapped between ring and groove?

In the groove area and bottom portion of neck flange where water was most likely trapped there is pitting and material loss with most severe pitting in groove area.

The unusual part is in side and upper areas of flange neck there are small dots less than 1 mm distributed where the machined surface has begun to breakdown and seem like pit initiation sites?

Please share any opinion or advice.

 

[Dhurjati Sen]

Dear mtk-14,

Yes, there could be Galvanic Corrosion between SS304 & ASTM A 350 Gr LF2.

From the pics, the corrosion seems superficial and not a cause of worry.

Regards.

DHURJATI SEN
Kolkata, India

 

[cap1a79]

Galvanic corrosion can happen in case two different metals are contacted in water service. For your case, it seems combined with crevice.
Check source of the water and prepare prevention method. ( Is the water comes from internal or due to improper storage before the use?(<--I have similar experience that rain water induced pitting on tank plate stored outdoor.))

Anyway, measure the remaining thickness after removing the rust area and check whether it has sufficient Min req thk + Corrosion allowance for rest of lifetime.


Lee SiHyoung,