Sumitomo Metal Industries, Inc.

Nippon Oil Fats Co., Ltd.

Sumitomo Metal Industries Co., Ltd.

Hiroki Hanabata

Hideo Kawaguchi

Takao Taka

Kiyoyuki Fukui

Toshiaki Shiota

Yukihiro Yoshikawa

Ryoichi Noumi

Hiroshi Fukudome

Hiromi Izaiku

Sachio Matsuo

Koichi Komai

Maki Itoh

Kisuke Yoshida

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 coating composition based on an acrylic resin which is useful for preparing lubricated steel products such as steel sheets or tubes is disclosed. The coating composition contains as additives a rust preventive which is a mixture of a sulfonamidecarboxylic acid and an cyclic amine and a water repellent. It exhibits improved rust-preventing properties when lubricated steel products having a coating film formed from the coating composition are stored for a prolonged period under coiled or stacked conditions.

Coating composition with improved rust-preventing properties for use in

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Ibaragi, Japan

Hiroki Hanabata