Galvanic corrosion of 316 1

[Lee.k]

I have some 316 St St brackets that will be welded to a 316 St St frame. These brackets will be in contact with Duplex piping, A790/S31803. The Duplex piping will be secured to the brackets with 316 u-bolts.

This assembly is an oil and gas skid that will be operating on an offshore platform.

Question: Should the 316 parts be electrically isolated from the Duplex piping?

 

[EdStainless]

Don't worry about that, the 316 will crevice corrode fast enough anyway.
the 316 and 2205 are similar enough in galvanic potential that that is the least of your worries.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Lee.k]

Will crevice corrosion attack:

* The area of the 316 brackets that will be contact with the Duplex piping?

* The 316 fasteners/u-bolt threads that will secure the Duplex piping?

* There brackets are welded to the frame but no welds are in contact with the Duplex. Are the welds susceptible to crevice corrosion?

If yes to any the above, what precautions should I take?

 

[EdStainless]

If 316 is out where it will be washed by rain then light surface pitting is all that I would expect.
the 316 welds are likely to show more pitting than other 316 parts but that is just life.
But you have threaded connections, it is very likely to crevice corrode under those.
And where the 316 clamps against the 2205 also.
This isn't an issue of the alloys but just of forming a tight crevice.

If this user has 316 everywhere and thinks that the condition is just fine then go ahead.
But 316 does not like accumulated salts getting trapped.
In crevices you will eventually get serious corrosion.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed