Lime scale can be one of the most difficult materials to remove from porcelain and tile. Lime, caused by hard water, is a chalky white substance that can grow in your toilet, tub, sinks and pipes. While a small amount of lime scale can be cleaned with vinegar or lemon juice, removing heavier deposits may require using a strong chemical such as hydrochloric acid. Pure hydrochloric acid is dangerous, as the reaction with lime scale creates a toxic chlorine gas. For safety, always ventilate the area and use a commercial cleaner containing hydrochloric acid rather than handling it full-strength.
Put on heavy rubber gloves and safety glasses, and open all windows in the area before using any cleaner containing hydrochloric acid. Turn on the exhaust fan, if you have one. Take any movable pieces outdoors to clean.
Spray hydrochloric acid cleaner directly on the lime scale until it's saturated, or apply it with a sponge. Leave the room and allow it to work for 5 to 10 minutes.
Scrub the lime scale off with a scrub brush. Rinse off the area. If lime scale remains, apply more cleaner and leave the room again for 5 minutes. Scrub the area again, and rinse. Repeat if necessary.
Maintain the surface by cleaning with 1 part hydrochloric acid cleaner mixed with 1 part of water one to three times a week, depending on the hardness of your water.