Metals compatible with Cunifer?

[thormj]

What metals are most compatible with cunifer pipes in saltwater?
We make sensors using
Stainless (no-go; corrodes quickly)
Monel (supposedly good for saltwater resistance, but it seems to be more away on the corrosion charts)
Hastelloy C4 / C22 (and I don't know which would be better)
Titanium
Tungsten

I've seen some studies that say Hastelloy C is a good match, but others say that Hastelloy C4 & C22 should be avoided in saltwater environments...

 

[EdStainless]

High alloy stainless grades, 6%Mo superaustenitics (AL-6XN), C-22, or Ti would all survive very well.
Galvanic corrosion is another issue. Monel 400 should be the closest, but I don't have any data.

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