Rustaid Fast Acting Rust Stain Remover Organic formula works with no rubbing or scrubbing. Rust stains simply disappear. Ideal for the removal of rust stains caused by bleeding hardware, thru hull fittings, fish hooks, tools and iron staining at the water line. Safe for application on fiberglass, concrete docks and seawalls, paint, wood, stainless steel, sail canvas, boat covers and most other fabrics and metals. Biodegradable.