GB996749A - Protective coatings for steel and other metal - Google Patents

Abstract

A method of forming a corrosion-resistant coating on a metal such as steel, Cu, Ni or Cr comprises contacting the metal at elevated temperature with one or more compounds which react with the metal to form an adherent coating of either (1) a chelate compound of the metal, or (2) an organo-metallic compound including a carbon-metal chemical bond, the temperature being above the melting point of the reacting compounds which may be in the liquid or vapour state but below the volatilization or decomposition temperature of the reaction product. Examples of (1) are iron ethylenediamine bis-acetylacetonate and iron 1:2:4 trihydroxyanthraquinonate, and examples of (2) are bis-cyclopentadienyl iron, enneacarbonyl iron disulphide, cyclooctatetraene hexacarbonyl iron, tricarbonyl phenyl mercaptide of iron and the reaction product of Fe and phthalimide. The enneacarbonyl iron disulphide is formed by the reaction of CO and H2S with steel. In an example, steel is exposed to an atmosphere of phthalimide vapour at a pressure of 1.25-2 atmospheres and temperature of 300-500 DEG C. The cut edges of steel sheet coated with Al may be protected in this way. Instead of forming the coating on a steel surface itself the latter may be provided with a thin layer of a metal such as Cu, Ni and Cr, e.g. by electroplating, and the coating of the second metal subjected to the action of the vaporized or molten organic compound.