2003 Volume 54 Issue 2 Pages 131-136
To improve the corrosion resistance to salt and acidic attack of magnesium alloy, composite films consisting of a chemical conversion film or an anodic oxide film and a coating layer deposited thereon were prepared by the sol-gel process using tetraethoxysilane as a metal alkoxide. These composite films prepared by repeating three or five dip-coatings indicated an excellent corrosion resistance to salt attack. Furthermore, the acidic corrosion resistance of composite film formed on anodic oxide film was examined using an electromotive force measurement test. In comparisons between the composite films prepared by repeating three dip-coatings and an anodic oxide film of magnesium alloy, the acidic corrosion resistances of these films to various acids increased by a factor of 12 to 33 on the anodic oxide film in the thickness of 7μm and a factor of 3.4 to 7.6 for thickness of 15μm. These improvement of corrosion resistance are considered to be caused by the production of some reaction products in the path of a salt solution or an acid that is penetrating into the composite film.
