Singerman Laboratories Rust Stain Remover for Concrete is the most effective cleaner in the marketplace for removing rust stains from concrete and natural stone. Great for concrete or masonry sidewalks, steps, patios, driveways, retaining walls, and brick siding. Makes the concrete or stone surface look like new. 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 of your hardscape 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. We also find there is some succes witht the removal of battery acid stains but may require multiple intensive application.