No Need to Remove Rust First! POR-15 is a high-tech, high performance rust-preventive coating designed for application directly on rusted or seasoned metal surfaces. It dries to an incredible rock-hard, non-porous finish that won't chip, crack, or peel, and it prevents rust from recurring by protecting metal from further exposure to moisture. Use it to coat rusty frames, floor pans, farm equipment, marine equipment, or even a heavily corroded battery tray. POR-15 is sensitive to UV light (sun) and must be top coated for prolonged exposure to sunlight. Top coating is not required for areas not exposed to sunlight.