PURPOSE:To improve corrosion resistance and paint adhesiveness, by applying a chromate coating film to the surface of an alloyed Zn-coated steel sheet, an Al-coated steel sheet, etc., and then forming thereon the film of compound organosilicate resin to which an oxyacid of Mo, W, V, etc. or a salt thereof is added. CONSTITUTION:A chromate coating film is applied to the surface of a Zn-coated steel sheet, a steel sheet coated with alloyed Zn, e.g. Zn-Fe, Zn-Ni, Zn-Mn or Zn-Al, an Al-coated steel sheet or a complex coated steel sheet on which these plating layers are formed under a multilayered condition. Thereafter, the coating film of complex organo-silicate resin prepared by adding one or more of oxyacids of Mo, W, V, Sn, B and Si and/or salts thereof to compound organosilicate resin contg. silica sol, organic resin and a silane compound is formed on said chromate film. This compound coated steel sheet is excellent in corrosion resistance, paint adhesiveness and in corrosion resistance of the coated state.
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