ELECTROPLATED Zn-Ni-SiO2 COMPOSITE COATINGS TREATED WITH A SILANE COUPLING AGENT TO REPLACE CHROMATING

The fixing of a silane coupling agent to Zn-Ni-silica (SiO2) composite coatings was studied for the purpose of developing a coating process as an alternative to chromating. The corrosion resistance of Zn-Ni-silica composite coatings was rem arkably improved by the silica nanoparticles in the composite, which were disper sed in the surface of this film. The silane coupling agent formed chemical bonds with the inorganic silica particles during the silane coupling treatment on the se composite coatings. The treatment suppressed the formation of white corrosion products to the same extent as chromating, as measured in salt spray tests. It is concluded that treating Zn-Ni-silica composite coatings with silane coupling agents is a viable alternative technique to chromating.