Question you salty sea dogs
Can or should I use stainless studs in a cast iron heat exchanger housing?
cheers
Loctite is not a insulator but when use it fills the voids and prevents moisture maybe PTFE tape . Ive not used Durlac yet but will be soon
Be aware that if you also use S/Steel nuts on your S/Steel studs, there is a change the thread may bind when tightened. Applying grease to the thread normally stops this.
If the Electrolyte (Salt water) does not come in contact with the S/Steel studs, then there shouldn't be an issues with electrolysis. The problem with S/Steel with regard to the normal studs is that they are further along the galvanic chart thus resulting is a higher voltage. But it is the casting that will suffer not the S/Steel stud.
Could be wrong again. 
