Dy-Mark Metal Pro Rust Converter is a tannic acid based rust converter specially formulated for the treatment of rusted surfaces. In one easy step, Rust Converter chemically reacts with the rust to form a black inert organic compound that binds to the surface and provides a barrier by sealing out moisture for effective rust protection. Suitable for use under most paint systems. For superior protection it is recommended to overcoat with Dy-Mark Primer and then Dy-Mark Metal Pro Quick Dry range of topcoat colours within 3 months of surface preparation with Rust Converter. Dy-Mark Metal Pro Rust Converter is ideal for use on gutters, roofs, garden furniture, fencing, gates, trailers, machinery and equipment. Does not contain Phosphoric acid.