Singerman Laboratories Rust Stain Remover for Concrete is the most effective cleaner in the marketplace for removing rust stains from concrete and natural stone. Makes the concrete or stone surface look like new. Frankly, we've been unable to find another product that actually removes rust stains from concrete, except those that are so harsh that they remove the stain by also removing the concrete. It is supplied as a white powder which is mixed with water just before application, forming a clear gel. The rust stain remover is spread on the surface and left for one to fifteen minutes, depending on the severity of the stain; the stain disappears without scrubbing. Rinse thoroughly to prevent redisposition of the stain. Will not harm grass or other vegetation.