Real Descaler is a blend of organic and mineral acids formulated to remove hard water scale build-up and scale/soil build-up and scale/soil build-ups from kettles, humidifiers, showers, tubs, coffee urns and dish machines. It is instantly soluble in water and remains stable through long storage. It will clean fiberglass (including boats and trailers). Real Descaler is not recommended for zinc and galvanized metal and mildly attacks magnesium and aluminum.