Nutserts are one thing you do NOT want corroded. That makes for BIG problems. And these nutserts are the same as poison spider and metal cloak etc.

They should make them out of steel and tack weld them to the body. Then you just spray paint the whole thing and your good to go.

I think the POR15 is good in this case, but only time will tell. (you probably won't ever take the flares off again in the future tho)