Rust, which is known chemically as iron oxide, is destructive to anything made of steel or iron. This is because as the rust forms, it creates small openings on the surface of the metal. These cracks then reveal more vulnerable metal to the atmosphere, leading to the formation of even more rust. Exposure to salt and moisture make the rusting process even more severe and rapid. You can, however, remove rust by making your own chemical rust-fighting solution. This will work for any rusted objects made of steel or iron, including rusty horseshoes.
Purchase some lye and powdered zinc oxide. Lye can usually be found at most hardware or garden supply stores. Contact your local pharmacies to see if they carry zinc oxide in powdered form. If they don't, the pharmacist should be able to point you in the right direction. You can also purchase powdered zinc oxide online.
Tie a piece of wire, approximately 12-inches in length, to the rusty horseshoe.
Find an old pot large enough to hold the horseshoe. Fill the pot approximately ¾ full of water and place the pot on your stove. Turn on the heat and begin adding lye to the water. With the lye, the water will not boil as it should at 100 degrees Celsius. Instead, you should add enough lye so that the water begins boiling at approximately at 132 degrees Celsius. Use your old cooking thermometer to help determine the heat of the water.
Add a few tablespoons of the powdered zinc oxide to the solution. The amount of zinc oxide does not need to be precise. Combined with the lye, the zinc molecules will become positively charged. The positive zinc molecules will then separate the iron oxide from the actual metal.
Use the wire you attached to the horseshoe to lower the horseshoe into the boiling solution. Allow the rusty horseshoe to boil in the solution for a while. Use the wire to pull the horseshoe out and check on the progress. The exact time it takes to remove the rust will depend on the severity of the corrosion.
Remove the horseshoe from the solution after you're satisfied all of the rust has been removed. Then place the horseshoe under cold, running water. Be sure to thoroughly rinse the horseshoe to both remove the solution and cool the metal.
Spray the entire surface of the horseshoe with WD-40. This will help displace any remaining moisture and protect the horseshoe from future rust.
Always wear protective eyewear and gloves when handling lye. Also avoid inhaling any fumes when working with lye. Do not wait for the water to boil before adding lye. Rather, begin adding it as soon as you turn on the heat. Continue to wear your protective goggles and gloves when working around the boiling water. Do not lean over the water and take extreme care to avoid spilling any water on your skin. Finally, avoid using glass cookware for this process. Not only can it break, it may lead to a situation where the water does not bubble when it boils. Extremely still, superheated water can explode upward when a foreign substance is added to it.