Hydrochloric (muriatic) acid is an excellent and effective way to clean rusty steel. However, it can also cause you great harm if it is not used properly. Be sure to use all safety precautions and work in a ventilated area to protect yourself from fumes. If necessary, consult an expert for further guidance.
Don all necessary safety gear, including goggles, thick clothing, work boots and filtration mask, which will protect you from vapors from the reaction of rust and muriatic acid. Find a well-ventilated area to work in; ideally, this will outdoors in an area with good air circulation.
Soak the steel in a hot solution of soapy water, for about 20 minutes. Then, wash the surface thoroughly with water.
Mix muriatic acid and water together, in a 1:1 volume ratio. As your chemistry teacher taught you, add the acid to the water, not the water to the acid. Place the steel in a nonreactive tub and pour the solution over the steel. Allow the solution to sit for about an hour.
Pour out the solution, and survey the steel to determine if the rust has been removed to your satisfaction. If not, try a 2:1 solution of muriatic acid to water.
Rinse the steel thoroughly with water. Neutralize any remaining acid on the steel and in the tub by making a solution of 1/4 cup of baking soda in 2 gallons of water, and adding it to the tub.
Drain the tub, and rinse thoroughly with water.
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