Modified nano-clays and coating compositions including the modified nano-clays are disclosed. The coating compositions are useful for protecting objects such as outdoor sculptures and architectural elements made of metal or including metal components. In some embodiments, the modified nano-clay is Laponite that has been covalently modified with (tridecafluoro-1,1,2,2-tetrahydrooctyl) triethoxysilane and cation-exchanged with phosphorylcholine.