Bronze is about 220 on the galvanic scale - about in the middle - which is why it is often used in marine applications - it tends to get along "pretty well" with most other metals on a boat.
Stainless Steel comes in about 100 different "flavors" - some are less than bronze on the scale, some more - and of course passivated SS is generally not a problem.
I would advise against Aluminum cotter pins, though.
also zinc. Stay away from zinc cotter pins.