I think it can be either. I have lug nut replacements and a mix of OEMs on my 987 that have rusted somewhat too.

Ford has entered the chat: “Amateurs!”

wheel nuts you lug nut

OEM, mine were like this as well when I bought my car used. Got a set of black ones in Jan 2019, those are not as bad from what I can tell, they barely changed at all.

My car’s 11yrs old and they don’t look like this. Doesn’t seem right.

Wheel acid eats the coating on the bolts, especially the old silver ones. Use less caustic cleaners.