http://www.kodiaktrailer.com/
Kodiak is one of the more popular disc brake setups in the US. Click on the Disc Brake link on the right. Options from all-stainless to Silver-Cadmium plated to E-coat (which I think is just zinc plating) to uncoated mild steel.
I haven't gone this route (mostly because my drum brakes haven't fallen apart, but partially because of the cost of retrofit), but one day... maybe.
Advantage of disc setups is that rinsing the components is a lot easier (everything's exposed.) They do tend to run a little hotter than drums, though (the pads are always in contact with the rotors, which generates some amount of heat while running.)
Given how my drums have held up (i.e. they really haven't), I wouldn't say that accellerated corrosion with discs would be a determining factor.
jky