any metallurgists out there?, page-5

it depends on where it was made as well.

some stainless is not (china) whilst the stuff from sweden or japan is better.

also how much salt is in the bore?

if there are dissimilar metals this will set up electrolysis but the way around that if the metals come in contact with each other is to use teflon washers
the steel should be austenitic with about 17% chrome content - this is 316

to be truthful i would be very wary about buying something like a submersible from a chinese manufacturer.

some types of stainless are magnetic souse one and have a look - if its magnetic its the wrong type for the purpose.

be careful undoing ss bolts too - they can seize up and youll stuff the threads. if youve broken the head off one use eaziouts to extract them but be careful drilling the pilot hole. ss is tough to drill and you should also use high quality drills. dont use crappy ones as they will burn out which you will know when you get a high pitched squeal when drilling. use tons of lubricant

the paste mentioned above is anti seize and yes its a good idea