A Chromium VI-free coating composition comprises a binder and a corrosion inhibitor in a solvent, wherein the binder comprises a silicate and an organic titanate, and the corrosion inhibitor comprises aluminium particles and zinc particles preferably flakes. The composition may also comprise an anti-corrosion additive which comprises a metal phosphate, a lubricant which comprises a polyolefin wax, and/or a thickener. The coating composition is useful for coating substrates such as nuts, bolts an...