An article which is resistant to corrosion or erosion by chemically active plasmas and a method of making the article are described. The article is comprised of a metal or metal alloy substrate having on its surface a coating which is an oxide of the metal or metal alloy. The structure of the oxide coating is columnar in nature. The grain size of the crystals which make up the oxide is larger at the surface of the oxide coating than at the interface between the oxide coating and the metal or metal alloy substrate, and wherein the oxide coating is in compression at the interface between the oxide coating and the metal or metal alloy substrate. Typically the metal is selected from the group consisting of yttrium, neodymium, samarium, terbium, dysprosium, erbium, ytterbium, scandium, hafnium, niobium or combinations thereof.