Masaaki Yamashita

Effects of Azo-metal Complex Dyes on Properties of Black Thin Organic Coated Steel Sheets

Effects of azo-metal complex dyes on properties such as lightness value were investigated to examine a black thin organic coating (1-2 μm) on galvanized steel sheet for electrical appliances. This product consists of chromate coating and black thin organic coating on an electrogalvanized steel sheet or a Zn-Ni alloy plated steel sheet. (1)Solvent azo-metal complex dye, solvent azo dye, carbon black pigment, and aniline black pigment were surveyed. The L-values of the thin coatings containing solvent azo-metal complex dye with 30-40 wt% content were less than 15, whereas the L-value of coatings containing carbon black pigment were more than 23. The dye was considered to be solved uniformly, although carbon black pigment aggregated in the thin coatings. (2)The weathering resistance of the coating containing azo-metal complex dyes was superior to that of coatings containing azo dyes. (3)The black thin coating containing azo-metal complex dyes can provide both good corrosion resistance and spot weldability. (4)Results demonstrate that the black thin organic coating (1-2 μm), consisting of azo-metal complex dye and organic resin, can provide a good black appearance, weathering resistance, corrosion resistance, and spot weldability.

Newly developed chromium-free organic-inorganic composite coated steel sheet with excellent corrosion resistance

From the point of view of ecology, there has been a trend of measurable advances in coated steel sheets for electrical appliances. For further advancement, completely hexavalent chromium-free coated products need to be developed. Despite the large amount of research of chromium free coating being carried out for many years, there have never been products that could provide excellent corrosion protection with a low cost treatment until recently. Recently, in response to the increasing demands for ecological products, new chromium-free coated steel sheets were industrialized independently by each of the six major steel companies in Japan in 1998. Those products were adopted for chassis and cases of audio-visual and office equipment. Features and practical characteristics of one of the new products, GEO-FREONTIER COAT (GF) developed by NKK Corp. are to be presented.