Isolation Gasket Kit between 304 & 316 SS

[DGrayPPD]

Hello all,

Just looking to ask a general question to improve my own knowledge of the subject.

I had an instructor talk about different metallurgy's and the need for isolation (or insulating) gaskets between flanged connections of differing materials due to the galvanic corrosion. Although I'm fairly familiar with this in terms of CS to SS connections, he stated most people miss that this practice should also be applied between 316 and 304 SS if used together. Now I can't say that I've had a project that involved the use of both 304 and 316 SS together in the same service, but I would still like to know if this is a common practice that I need to be aware of in the event the situations presents itself in the future.

What are your thoughts?

"Thinking is the hardest work there is, which is probably the reason why so few engage in it."

-Henry Ford

 

[EdStainless]

Usually it isn't used between 304 and 316.
If they are both well passive (no active corrosion) then the potentials will be nearly identical and there is no reason to isolate them.
I have seen cases where it was expected that the 304 could corrode, so isolation was used to slow that down.
This case is rather rare. If you are building equipment you would just build it all out of the same alloy. I have only seen it where they have been forced to tie into older equipment.

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P.E. Metallurgy, Plymouth Tube

 

[DGrayPPD]

Thanks EdStainless,

What he was saying made sense to me, as I remember from back in the fab shop days having to specify dissimilar welds for P8/P8 on the pipe spool sheets so that the correct welding rod was used, however I have no actual experience performing the welding side of things. At least not yet anyway. So my thinking was if you had to specify a certain welding rod, then specifying a certain isolation gasket made sense as well. But I still questioned if this was a common everyday practice in industry.

Thank you for helping clear that up.

"Thinking is the hardest work there is, which is probably the reason why so few engage in it."

-Henry Ford

 

[Chumpes]

hello
SS 304 and SS 316 are very similar and i believe galvanic coupling will be negligible with that association.
regards

 

Any nearby weld between common base metals will cause a more distinct galvanic effect than any 304/316 couple.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."