]i have a metal shop, thankyou, just across a bridge from me-- best pricing i have found---i just needed to know which barrell to pull from--thankyou everyone--- is awesome!!!
Advice on the internet is worth more or less what you pay for it. If you want the expert advice your OP suggests, you will find it from a metals engineer... either pay fairly for a quick consult, or try talking to a steel outfit like Sandvik with a view to sourcing their product, they will be happy to advise - and will have people that actually know what they're talking about.
My opinion if you want it, based on limited professional experience with stainless steels in the marine environment, is to stay away from the 3xx series, including 316/L. The leisure marine industry has habitualized its use of 316 as a "marine grade", with production boat builders using it for no reason other than they always have. You then end up replacing chain plates after 10 years - go figure.
For many applications, and I would suggest chain plates is one, 316 is quite inappropriate to use on boats. It's PREN (pitting resistance) value is way too low, as are its critical crevice and pitting temperature points, it's too prone to stress cracking, too vulnerable to chlorides.
(p.s.: do
not use 304)
I would use a duplex plate, 2205 is a standard, a super duplex like 2507 would be nice but expensive. All duplexes have better corrosion properties than 316, elevated PRENs and resistance to SCC, and far superior mechanical properties. They are more expensive, but also double the strength, which means you can cut weight and reduce section sizes, so design cost on a strength-for-strength basis can probably be kept similar.
I could go on but Google will quickly give you product sheets from the likes of Sandvik. At the risk of repeating myself, be sure to qualify advice you receive.
