A primer coating system is disclosed that is resistant to abrasion and corrosion and includes a basecoat or first layer comprising a resinous polyepoxide, an aminoplast, phenoplast or blocked isocyanate curing agent, an epoxy-phosphate, a chromium-containing pigment and a clay that has the capacity to fix phosphate. The system may further include an overcoat or second layer comprising a resinous polyhydric alcohol, a polyisocyanate, a chromium-containing pigment and the foregoing clay, and a third layer of a finish coating preferably based on a fluorine-containing polymer.