Sunnyside® Back to Nature® Ready-Strip® Rust Remover Spray is an environmentally friendly, water-based, biodegradable, and nonflammable remover of rust spots and stains. Rust is the result of a chemical process called oxidation and can stain anything it touches. This rust remover is noncorrosive and does not contain phosphoric or hydrochloric acid. It removes most rust spots and stains from interior and exterior surfaces including concrete, toilets, sinks, bathtubs, appliances, clothing, upholstery, metal, wrought iron, house siding, sporting goods, and more.