Muriatic acid is a strong chemical cleaner that home builders use to smooth porcelain and fiberglass surfaces. The strong acid can actually eat away surfaces. To use the chemical to remove rust stains, dilute it and take the proper precautions so it doesn't damage your surface or sting your eyes or lungs or irritate your skin. Use muriatic acid to clean rust from porcelain, fiberglass, bricks and tiles. Do not use it to remove rust from stainless steel surfaces.
Things You'll Need
Put on rubber gloves, a dust mask and goggles. Fumes from muriatic acid can make your eyes sting; contact with the chemical will dry out your skin.
Open the windows and doors in the area to ventilate the workspace.
Fill a bucket ½ full with water.
Fill the other half with muriatic acid. Mix to combine.
Dip a brush into the solution. Don't let the solution touch your bare skin.
Apply the solution to the rusty area.
Let the solution sit on the rusty area for at least 1 hour. Reapply the solution with the brush if the surface dries out. Never leave the muriatic solution or the area unattended if there are children or pets in your home.
Scrub the rust away.
Immediately rinse the area with clear water to prevent the muriatic acid from eating its way through the surface.
Let the area air dry completely.