Muriatic acid mixed 50/50 with water. DO NOT use it inside the garage. Use it outside. Once the part is clean, dump out the acid(into another container) and pour in water with a lot of baking soda in it. That will neutralize the acid. Then rince with clean water. If that's all you do, the part will start rusting right away. I found that if you soak, or rub down the part with a little EvapoRust, that keeps the part from rusting.
After the mast came out of the baking soda water, I dipped some 0000 steel wool in EvapoRust and rubbed it down. I rinced with clean water and used compressed air to dry it. It sat inside my house for a week before going to the platers. It never started to rust.