I believe the body of the gen is
aluminum so a couple of options.
First, best, but most
work. Disassemble the unit and take the case to a local shop that does powder coating. This a bit of a pain and the case would have to be completely stripped of everything: gaskets,
seals, any attached
parts, etc and the powder coating would probably clog all the threads and screw holes in the case requiring clearing all the threads with a tap.
Second option, I have had very good luck using Pettit Alumaprotect primer. It is a 2 part
epoxy primer that bonds to the
aluminum and provides a tough base for an outer coat. I used another Pettit
paint for the finish coat to be sure of compatibility (it was one that they recommended for this application), Pettit Easypoxy one part.