Muratic acid is a reactive chemical acid. It can cause black, scorched-like stains on stainless steel or discoloration stains on grout and tile.If not removed, it can eat away at the grout. Once the muratic acid works its way into stainless steel, grout or tile, it can be hard to remove. While some large muratic acid stains may be impossible to remove, small or minor stains should be able to be removed with proper treatment. And, even if the stain is unable to be completely removed, treatment should improve the appearance, color and size of the stain.
Add 2 tbsp. of baking soda to 2 tbsp. of water in a bowl. Mix together to create a paste. If the paste is watery, add a bit more baking soda; if the paste is too thick, add a bit more water.
Use a cloth to rub the paste into the muratic acid stain. Allow the mixture to sit on the stain for 10 to 15 minutes.
Wet a soft cloth and wipe away the mixture. Repeat as needed to remove stain.
Tile and Grout
Dip a soft-bristled brush in a phosphoric acid masonry cleaner. Apply the cleaner to the stain.
Watch as the cleaner works into the stain. Wipe the cleaner away with a sponge or cloth when it looks like the stain is lifting. This can take as little as 10 to 15 seconds, but the cleaner should not be left on for more than one minute. Repeat as needed to remove the stain.
Mix 1 cup of ammonia to 1 gallon of water. Dip a sponge in the mixture and thoroughly clean to get rid of any traces of the phosphoric acid masonry cleaner.