An article comprises a body having a protective coating. The protective coating is a thin film that comprises a metal oxy-fluoride. The metal oxy-fluoride has an empirical formula of MxOyFz, where M is a metal, y has a value of 0.1 to 1.9 times a value of x and z has a value of 0.1 to 3.9 times the value of x. The protective coating has a thickness of 1 to 30 microns and a porosity of less than 0.1%.