Sumitomo Metal Industries, Inc.

Nippon Oil Fats Co., Ltd.

Sumitomo Metal Industries Co., Ltd.

Sachio Matsuo

Takao Taka

Kiyoyuki Fukui

Toshiaki Shiota

Yukihiro Yoshikawa

Ryoichi Noumi

Rikizo Kobashi

Tadashi Sakane

Hiroshi Fukudome

Hiroumi Izaiku

Hideo Kawaguchi

Hiroki Hanabata

Shinji Fujiwara

Maki Itoh

Toshinari Yazawa

A precoated steel sheet having improved corrosion resistance and formability is disclosed, which comprises a Zn- or Zn alloy-plated steel sheet having on the plated surface either a colloidal silica-containing chromate undercoat layer and a polyhydroxypolyether resin-based topcoat of 0.3 to 10 .mu.m in thickness in which resin is derived by polycondensation of a dihydric phenol component selected from a mononuclear dihydric phenol, dinuclear dihydric phenol, and a mixture of both, with an epihalohydrin or a non-colloidal material-containing chromate underlayer and an epoxy resin based topcoat containing colloidal silica of a thickness of from 0.3-1.6 .mu.m in thickness. In spite of the absence of zinc powder, the precoated steel sheet can be satisfactorily welded by resistance welding when the thickness of the topcoat layer is not greater than 2.5 .mu.m, and even with such a thin topcoat, the precoated steel sheet retains its improved corrosion resistance and formability. The precoated steel sheet can be satisfactorily finish-coated by electrodeposition. The undercoat layer is produced by a two stage reduction of Cr.sup.+6 to Cr.sup.+3 in an aqueous suspension containing chromic acid.

Precoated steel sheet having improved corrosion resistance and

A method of applying electrodeposition coating onto metallic material by continuously passing the metallic material through an electrodeposition bath comprising an alkaline-solution soluble resin, solid lubricant and water is disclosed.

Electrodeposition of lubricative coating

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Takatsuki, Japan

Sachio Matsuo