Thanks for the clarification John. The gallon jugs of is what you want not the Navel Jelly stuff. Its cheaper and doesn't have the fillers as John mentioned.
The last jug I bought was from Home Depot's masonry section and was sold as "Clean Strip" Prep & Etch". It's used to etch concrete and masonry. I used it to remove rust from three T-head engine cylinder blocks after degreasing and paint removal in a hot lye solution. Before using the Phosphoric acid I protected the bores with a coat of grease.
Another option is a quick coat of rattle can paint. When its time to finish the part or use it you can easily strip the paint off with a soak in lacquer thinner. Use a top coat - primer, unless its a sealing primer it will do little to protect from corrosion.