Yes, limescale remover typically contains acid. Limescale is a deposit of calcium carbonate (CaCO3) that can build up on surfaces that come into contact with hard water. Acids, such as hydrochloric acid (HCl) or sulfamic acid (H2NSO3), are used to dissolve limescale deposits. These acids react with the calcium carbonate to form water, carbon dioxide, and calcium chloride (CaCl2). The carbon dioxide gas escapes into the air, while the calcium chloride remains in solution.