Refinishing the outside of a claw foot bathtub yourself can save you a lot of money and is easy to do. While resurfacing the inside is better left to a professional (though it is tempting to purchase the $20 refinishing kit at your local home improvement store), the outside is much easier and more forgiving.
Antique cast iron bathtubs come in a wide variety of conditions and sizes, which adds to the appeal to many. The first thing to do is to assess the condition of the tub- how much rust is there, is the tub rusted through, does it have any “thin” spots? If you have any doubts about the condition of the cast iron itself or if you are concerned that the tub might not be structurally sound anymore due to extensive rust damage, consult a professional and save yourself the hassle of having the equivalent of a bathtub full of water flooding your house.
However, in most cases, cast iron bathtubs hold up very well over the years. Rust covering the otherwise intact outside of the tub is nothing to be concerned about, nor is it unusual. The first step to refinishing your bathtub is to deal with this rust. Keep in mind that there is a very good chance that, if there is any paint at all left on the outside of the tub, it could be lead paint. Proper precautions absolutely apply here, and you should protect yourself with a respirator at minimum and consider beginning the restoration in a garage or other open area with plenty of air. Even if you do not see any paint left on the surface, it is still wise to take steps to protect yourself.
Wearing your respirator, begin by cleaning off the outside of the tub thoroughly with a strong cleaner. Once the tub has dried, sand the first layer of rust by hand to prevent clogging your sander or grinder and to prevent more particles than necessary from flying through the air. When most of the obviously flaky rust is gone, move on to using an electric sander or an angle grinder with a metal brush to smooth the surface. The goal is not to remove the rust, but to make a smooth enough surface to allow paint to adhere and to look attractive. You may need to use a small metal brush to scrape the rust from the crevices in the ornate feet.
When your surface is smooth, wash the bathtub again, taking care to remove all the dust you’ve created by sanding. After allowing your tub to dry, coat the outside of the tub heavily with a primer specially made to prevent rust and to go on metal surfaces. You’ll need two coats of primer at minimum to get proper coverage, and the goal should be to only need one coat of paint.
Check the surface again for any rough areas or rusty spots which show through the primer. Your last step is to put at least one coat of a good quality oil-based paint on the tub. Latex will not give you as much of a sheen and won’t go on as smoothly, nor will any sort of spray paint, no matter how tempting.
Finishing your bathtub yourself is a worthwhile, satisfying experience which can also save you substantial money. And there is no better reward than a beautifully restored antique tub for soaking in the evening after a long day.