...actually, I ripped a mudflap off backing into the driveway and when I removed the ss sheetmetal screws, the fender lip around the hole is rusting.

Are the bodies made of galvanized steel?

Well, that doesn't matter I guess, the surface is galvanized but not the area where a drill punches through. I have visions of the truck looking like a 1977 Chevy that spent it's whole life in Michigan in a few years.

 

Best thing s to clean that right up and silicone you holes and screws before putting them in there. Too bad that wasn't done right the first time. I'm dealing with that right now.

 

I personally don' t like silicone. It is acidic, and encourages rust on ferrous metals. I agree to use a sealer, probably a better choice is urethane caulk or good old fashioned butyl caulk. It stays pliable and somewhat tacky. Sold at home depot for about $3.00 a tube. Also known as lap sealant or gutter sealant. It's the same stuff auto restorer's parts places sell for sealing seams in body panel and such, only half the price. Kevin