A self-priming rapid curing chromate free corrosion resistant coating composition based on a random polyvinyl terpolymer and an alkyd resin with a hydroxyl number between 80 200 in association with a mineral acid catalyst, at least one organic solvent and a drying agent wherein the vinyl terpolymer is predominantly a polyvinyl formal with polyvinyl alcohol and polyvinyl acetate as the other two co-polymers, the terpolymer cross linking through its hydroxyl groups with the alkyd resin in the composition during curing. The composition can be applied as a clear coat or as a pigmented composition with addition of pigments on ferrous and non-ferrous metallic substrate and is suitable for continuous coil coating lines. A method of coating a ferrous and non-ferrous metallic substrate by applying a coating composition on its surface and coated articles so produced.