Rust can eat through any metal surface. When metal is not properly protected from moisture, the rust attacks and begins to weaken the metal. If you catch the rust before it eats all the way through the metal, you can repair it pretty simply. Once the metal has created a hole in your bathtub, you will need to replace it. Replacement isn’t easy or cheap. If you aren’t ready to invest the time and money to replace the tub, use a patch kit. Patching the hole can provide a temporary solution to keep your tub working until you can replace it.
Sand the rusted area with medium-grit sandpaper. Remove all traces of rust. Continue sanding until you have a smooth surface around the hole. Wipe away sanding dust with a damp rag.
Dip a clean rag in acetone. Rub around the hole to remove oils, soap scum and residue.
Cut a piece of waxed paper to fit over the hole with ¼ inch overlap on all sides. Attach the waxed paper to the tub underneath the hole with painter’s tape. If you don’t have access to the underside of the tub, leave the waxed paper unattached.
Mix body filler according to manufacturer instructions. Choose a repair paste that is appropriate for your tub. Fibreglass and steel putty are available at automotive repair retailers.
Scoop out enough paste to fill the hole. Fill the hole with the waxed paper as a backing. Overfill the hole so that it comes out and overlaps the tub’s surface. If you are working with a loose piece of waxed paper, spread a thick layer of the paste on the waxed paper and press it over the top of the hole. Tape down with painter’s tape.
Let the putty harden overnight. Peel off the waxed paper, leaving the hardened putty in place. Sand the putty with fine-grit sandpaper to create a smooth surface. Wipe away the sanding dust.
Enamel spray paint can help to blend the patched area with the rest of the tub. Spray the area lightly with the paint. Apply two to three coats.