A powerful blend of acids formulated to remove rust stains from concrete, fiberglass, stone, tile as well as brass. Removes rust, welding scale, heat marks , light oil and shop soil from carbon steel and iron. It is also effective for removing light oxide and tarnish from brass, copper or copper alloys (brass, bronze and monel). It produces a hard thin surface conditioning on steel that serves as an excellent base for paint or other organic coatings. May also be used to remove rust from fiberglass boat hulls and decks; will not harm gel coat. pH 1.0 Use dilution: straight to 40 oz/gl.