[suicideneil]

I think you're treading a fine line on that being a warrenty void, but thats besides the point- corrosion X or someother fairly thin conformal waterproof coating would be fine to use- a few light coats on the underside of the PCB & on the top side, just mask off the heatsink.

Dont drive through any ponds though; I wouldnt do that with an un-touched MMM or any other esc for that matter..