We paint part of an inner fender, with some left over por-15. It accidently got left outside for a couple weeks in the sun. It turned a lite white color, that rubbed off on your hands. The can says not to let it be exposed to sunlite, and to top coat it, by sanding with 600 grit paper, and using there paint. The top coat in a lot duller black than the por-15. This stuff is tough. I've heated part for bolt removal, when i missed a broken one. The torch didnt even phase the por-15. Niether did my sand blaster. The only thing that takes it off well is the angle grinder.
