In terms of using stainless fasteners in aluminum; standard practice is to coat them with one of the various compounds which will electrically isolate one from the other.
Tef-Gel is a common one, & for bolts that I want to isolate, but ensure that they stay put, Blue
Loc-Tite is in my "bag of tricks".
And "Blue" is underlined, so that you don't use Red, or something similar, which is almost sure to guarantee destroying something, when you go to try & remove the fasteners.
There are others as well; Duralac (sp?), & some folks will use Never-Seize: Although the molybedenum in it strikes me as making it's use questionable for long term app's involving Aluminum. Given "moly's" place on the galvanic scale.
And in a pinch, some guys will even use fingernail polish (BTDT). Or for other app's, epoxy
of one sort or another is called for.
Though to be certain of your work, & the efficacy of your isolating agent, you can just disassemble things with some regularity... while being gentle on the threads, that is.
Also, if you're Really concerned about galvanic corrosion
, you can us aluminum fasteners. So that the mast wall, at least, will be "safe". Though you'll still need to paint
the undersides of the aluminum bolt heads, where they meet the mast steps.
Plus: As a tip for the maximum efficacy of your steps. Mount enough of them, closely enough together; so that it's easy for your shortest crew member
to climb up them, while wearing several layers of heavy clothing
. This, when the boat's bouncing around a lot.
That, & locate the top most pair (or pairs; for folks of greatly differing heights) so that the headboard & shackle are positioned at chest level for the shortest crew member
. As at that height, it's easiest to simultaneously hold onto the mast, & work on things/the head
of the sail.
: If in doubt regarding any of this, talk to your local rigger. And or, hire them for an hour or three of their expertise & instruction.