BRC-6000 Rust Conversion Primer is designed to chemically convert the iron oxide surface of rusty metal to a stable material called iron tannate. Iron oxide will continue to rust and needs to be treated to stop that process. Some companies use chemicals like phosphoric acid to accomplish this but the only true conversion occurs in the presence of tannic acid which is used in BRC-6000. Simply brush the rusted surface lightly to remove loose rust, wash with clear water to remove any soluble salts, let dry and then coat with BRC-6000. The conversion happens as the liquid turns from gray to black. BRC-6000 also contains a latex polymer that then acts as the primer. In normal atmospheric conditions, topcoat BRC-6000 as soon as it is dry. In very harsh applications, another primer, like Steel Plus Epoxy Primer may be needed over the BRC-6000 for longest term protection.