Industrial Metal Roof Rust and Screws Backing Out

We purchased some light industrial buildings in Houston that were built in the 1970s and 1980s. There is rusting but its not that bad and it barely leaks. Should we be doing some preventative maintenance to stop future rust or wait to do a complete recoating. If we do recoat, do you have any suggestions? Some roofers have suggested replacing all of the screws that are backing out, but like I said before we rarely have leaks. Keep in mind that we have over 200,000 SF of roof. Thanks for the advice.

Loose screws are a problem that gets worse fast, as the first place water goes is in the screw hole, creating rot. Rot makes the screw looser and prevents repair.

Right now, before it gets too bad, you can get the "next size up" neoprene gasket screw, making sure it's good quality. Get a proper roof harness. And test each screw: any that are loose at all pull out and replace with the bigger screw. The new screw will make it's own bigger hole: nothing special required.

Or even better mix up a little Smith's epoxy and draw it into a syringe. As you remove each loose screw, squirt Smith's into the hole, then add your new longer/fatter replacement screw. The combination of the two will make for a long lasting bulletproof repair.