Sumitomo Metal Industries, Inc.

Hiroshi Oishi

Yoshihiko Hoboh

Masanori Tsuji

Tadashi Nonaka

Kazuyuki Fujita

Naotaka Ueda

Atsuhisa Yakawa

Yasuo Shimada

Tomio Kondo

Hisakazu Morino

Akira Maruyama

Kazuhide Oshima

Yoshikazu Yamanaka

A continuous multi-layer plating line for steel sheet which includes a hot-galvanizing apparatus to form a galvanized coating and optionally to alloy the coating and an electroplating apparatus to form an electroplated coating on the galvanized coating. Between the hot-galvanizing apparatus and the electroplating apparatus, a post-galvanizing surface treatment apparatus effective for removing surface oxide contaminants and activating the surface of the galvanized coating is disposed and the galvanized steel sheet is treated thereby prior to electroplating. The post-galvanizing surface treatment may be carried out by applying an alkali solution or an acid which can dissolve aluminum oxide to the galvanized coating, by alkali electrolysis, by cathodic electrolysis, by cooling the galvanized steel sheet with an alkali solution, or by skin-pass rolling using an alkali solution or an acid which can dissolve aluminum oxide as a skin-pass roling liquid.

Electroplating of hot-galvanized steel sheet and continuous plating line

A process for direct zinc electroplating of aluminum strip which can be performed continuously at a high speed and a high current density. The process comprises pretreating aluminum strip by alkaline degreasing and then pickling and subjecting the pretreated aluminum strip to zinc electroplating in an acidic zinc plating bath which contains, in addition to Zn.sup.2+ ions, metal ions selected from the group consisting of Ni.sup.2+ ions and Fe.sup.2+ ions in a concentration of at least about 10 g/1 to form a Zn-Ni, Zn-Fe, or Zn-Ni-Fe alloy plated coating, which may be overlaid with another zinc electroplated coating.

Process for direct zinc electroplating of aluminum strip

A low carbon steel sheet dip-plated with a Zn-Al alloy, which is in a non-recrystallized and rolled state and which comprises, as an element to raise the recrystallization temperature, at least one of Ti: 0.01.about.0.40% by weight, Nb: 0.01.about.0.10% by weight, and B: 0.001.about.0.010% by weight, and a process for the manufacture thereof which comprises carrying out dip-plating at a temperature lower than the recrystallization temperature.

Steel sheet dip-plated with a Zn-Al alloy and process for the

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Wakayama, Japan

Hiroshi Oishi