These stains are caused by metallic objects such as steel wool, nails, flower pots, cans, etc. in the presence of moisture. Superficial stains may be removed by vigorous scrubbing with a non-abrasive material and a neutral cleaner. Seated stains are often affected by the application of a commercial “Naval Jelly” or “Rust Remover” that is neither high in acid or alkaline. Follow manufacturer’s directions carefully.