Owners of metal bathtubs coated with porcelain enamel often find rust begin to eat through the porcelain coating after years of use, resulting in a hole. To avoid having your entire tub rust out, you'll have to take steps to repair the hole. An epoxy mixture will fill the hole and harden after only a couple of days, leaving you with a repair that's both durable and waterproof. Adding a little shine with the use of a porcelain repair kit will hide the repair.
Remove any rust around the hole with the use of a stiff wired brush. Brush the rusted area only. To avoid scratching the undamaged areas of the bathtub, brush slowly and gently; the wire bristles will remove the rust without a great deal of force.
Dip a cloth into cold water and clean up any debris left from the brushing. Pour a mild detergent around the hole, cleaning the affected area thoroughly. Dry with a clean cloth. The area must be completely clean and dry prior to repairing it.
Mix epoxy resin and epoxy hardener in a small pail. Most epoxy resins and hardeners require a one to one ratio, but some manufacturers may call for a higher resin to hardener ratio.
Pour the resin and hardener mix into the hole. Fill the hole with the epoxy until the mixture is even with the bathtub. Allow the epoxy to dry, which typically takes around 48 hours. If the epoxy is not flush with the tub, sand down the uneven parts with sandpaper after the mixture dries.
Use a porcelain repair kit to paint over the epoxy and make the area look new. Porcelain repair kits come with a small brush that allows you to paint the product onto chips and repaired areas. Apply a thin coat, let dry, then apply a second coat. Sand the area lightly with sandpaper to make the surface flush with the porcelain surface. Buff the repaired area with a white cloth.