Wow,
tough one.
Perhaps a small strip of that 3m paint protector some of the fellas on here are using.
Otherwise, keep a bottle of touch up paint handy if you ride your bike, stuff will happen I guess....
Mine is chipped and I used some touch up paint on it. Doesn't match well and I am not sure why I even bothered, I have fiberglass fenders so no rust corrosion.
I pretty much don't pay attention to it.