Remove all the rust. You may decide to use a power sander for this if the rust is very severe. Use the sandpaper to scrape the rust away, but do not use heavy pressure since portions of the tub may be rusted partially through.
Clean the tub thoroughly. Use a cleaning rag and the liquid cleaner to get every speck of rust and dirt out of the tub. Make sure that it is completely dry before you continue.
Fix any nicks, scratches and gouges. Use the trowel to layer on the fiberglass putty. Most putty kits come with the putty and a hardening agent that is added just before you use the putty. However, measurements vary, so you will need to refer to the specific measurements for your product. Generally these types of "mends" take about 3 hours to set. Get the mend as close and flat to the surface of the tub as possible so that you can minimize sanding later.
Sand the mended areas. You want them to be flush with the rest of the tub. They may not be the same color, but they need to be smooth and flat.
Use a rag to apply a thin, even layer of the enamel bonding agent. This will help your paint stick to the surface of the cast iron tub and also help the finished result look even everywhere, including over the mended parts. Once you have applied the stain, you will need to wait about 2 hours for the tub to dry completely.
Paint the tub with the acrylic urethane enamel paint. Use the paintbrush or a rag to apply the paint. Use thin, even coats. It should stick to the bonding agent, but do not spread it so think that you can see the cast iron beneath the paint just in case. Once the first coat has dried (can take up to 5 hours), you will probably want to apply a second coat to make sure the paint is thick enough and totally even.
Things You Will Need
- Sand paper
- Fiberglass putty
- Enamel bonding agent
- Cleaning rags
- Tub cleaner
- Paint brush
- Acrylic urethane enamel paint
- Use a paint spray gun to get a more even finish on their tub. Be sure that the area is well ventilated before you start bonding and painting.