The main purpose of chromate treatment is to improve anti-corrosion by conversioning a metal surface.But hexavalent Chrome (Cr, Cd, Pb, Hg) is considered carcinogenic and has been banned in many areas of the World. This paper made a Coating Layer Structure and anti-corrosiveness study on Tannic Acid-H2TiF6/SiO2 composite coating from hot-dip galvanized steel sheet，it is Investigating the coating Corrosion relations on PMT, pH and film thickness. The optimum operation condition is at pH = 3 and in the PMT range of 60-80 degree centigrade.
