Muriatic acid is hydrogen chloride gas dissolved in water; many know it as hydrochloric acid. It is often used on masonry to etch the surface in preparation for paint or epoxy; etching degrades the surface so it is more receptive to the paint or epoxy. Use caution with using muriatic acid; it can cause permanent blindness if you get it in your eyes, and can severely burn your skin. Wear acid-resistant gloves, rubber boots, a long-sleeved shirt and pants, safety goggles and a respirator with an acid-grade filter. Keep a neutralizing agent handy with a garden hose and water at all times; and the outdoor area where you are working should be well-ventilated. Muriatic acid should not be used indoors.
Tape an acid-resistant covering to the walls and trim around the floor, using painter's tape. Cover up to 12 inches up the wall.
Cover adjacent plants or foliage with the acid-resistant covering to protect them from overspray.
Mix a solution of muriatic acid and water, with 10 parts water and 1 part muriatic acid, in a bucket.
Pour a puddle-sized amount of the muriatic acid solution on the floor. Scrub the area with a power scrubber. Use a bristle brush with a long handle to scrub areas adjacent to the wall and in corners that the power scrubber won't reach. Continue scrubbing the floor until you've covered the entire area.
Spray water over the floor with a garden hose a few times to wash off the muriatic acid. Remove the pads from the power scrubber and rinse them off with the water. Rinse the bristle brush with water.
Replace the clean pads on the power scrubber. Spray an area with water and scrub the area with the power scrubber. Scrub the entire floor with the scrubbers.
Rinse the entire floor two more times with water to remove all the muriatic acid solution.