Red Lead is a bright red to orange-red powder, used Lead glass, and red pigments; a paint made with Red Lead is commonly used to protect iron and steel from rusting. Chemically, Red Lead is Lead tetra oxide, Pb3O4, a water-insoluble compound that is prepared by the oxidation of metallic Lead or of litharge (Lead monoxide);Red Lead primer is one of the oldest and most commonly used anti-corrosion pigments applied to metal surfaces.