It depends on the grade of stainless actually. I’ve never run into “proprietary 30X stainless” but I have plenty of experience with 304, 308, 309, and 316. 309 can rust on you, but I’ve never seen 316 rust outside of ludicrously corrosive environments.
I have what’s known in the industry as “magic piss fingers”. What that means is that I am a salty, sweaty man who can rust just about anything rustable simply by touching it with my bare hand. That being said, I haven’t managed to get a single speck of rust on my welded 316 hammer in 12 years of using it.
Nickel. It provides both corrosion resistance and increased ductility which makes the material more likely to bend before breaking. I like using it to weld onto busted taps to try to back them out because the weld will flex a little bit instead of just snapping off.