Bought several packs of KD #805 couplers. They are all infected with some kind of grayish-white substance. Does anyone know what this is and, more importantly, how to clean it off? Even scraping doesn't work very well.
I have seen that also on older packs or old couplers in my parts drawer. I paint my couplers "rail brown" and I just paint over it.
It does not seem to be like zinc pest or cause any weakness.
Don't worry about it, I have some couplers with that "powder" that are many years old and have no problems at all.
Depending on how old the couplers are and where they have been stored, it might be powdery mildew. No big deal, just give them a washing with a disinfectant cleaner (no bleach, it might etch the metal) or spray/dip them in alcohol to kill the mildew.