FWIW this was my procedure. Removed drain/screen, sanded rust/corrosion, sprayed it with Ospho, used two part resin (for auto/boat fiberglass repair) to fill damage, finish sand, apply epoxy paint over repair. You absolutely have to get it clean before covering it with paint. About 20 years later the repair still looks new.
dpunisher t1_jeeh4w0 wrote
Reply to I cleaned a rust stain near my bathtub drain and noticed the porcelain/enamel is gone and it is now bare metal. Is there any way to repair this to prevent future rust? by Sevitrey
FWIW this was my procedure. Removed drain/screen, sanded rust/corrosion, sprayed it with Ospho, used two part resin (for auto/boat fiberglass repair) to fill damage, finish sand, apply epoxy paint over repair. You absolutely have to get it clean before covering it with paint. About 20 years later the repair still looks new.