Tile cleaning can prove frustrating, especially if the tile has become riddled with difficult rust or mineral deposits. Certain types of tiles can benefit from the cleaning properties of phosphoric acid, particularly when other cleaning solutions fail. You must consider certain caveats, though, since not all types of tile will benefit.
Phosphoric acid is a weak acid, similar to acetic acid and sulfamic acid. You can find phosphoric acid in soft drinks, as well as in some commercial detergents and cleaning agents. You can use any commercial cleaners with phosphoric acid to clean your tiles, just as long as the tiles are acid-safe.
Phosphoric acid works effectively as a rust remover. If left on a surface such as tile for an extended period of time (at least an hour), it can gradually break down and loosen mineral deposits, making it possible for you to simply wipe them away. For example, cola soft drinks can remove rust from toilets specifically because of their high concentration of phosphoric acid. Since phosphoric acid is noncorrosive, you need not worry about any dangers or health risks associated with it.
Certain types of tiles should never come into contact with phosphoric acid. In particular, you must avoid using phosphoric acid cleaners on any natural-stone tiles, as even mild acids can cause etching in and even dissolve natural stone. For example, while you can use phosphoric acid on ceramic, porcelain and composite surfaces, you should never attempt to use it on natural marble, onyx, granite or limestone.
Choose a commercial cleaner containing phosphoric acid and dilute it with water if instructed by the manufacturer. Apply it directly to your tile surface and scrub using a mop (for floors) or sponge. If you have mineral deposits on your tiles, allow the phosphoric acid solution to absorb the minerals for at least 15 minutes before you begin scrubbing. Rinse with water and then dry your tile surface by hand to prevent spotting.