Nippon Kokan Kabushiki Kaisha

Masaru Ohmura

Takeshi Adaniya

Tsutomu Watanabe

Kazuo Matsudo

Masahiro Shoji

In a process for manufacturing an electro-galvanized steel strip, which comprises: moving a steel strip in an acidic electro-galvanizing bath containing cobalt and chrominum in parallel with the plane of at least one anode plate to subject said steel strip to an electro-galvanizing treatment, thereby forming, on at least one surface of said steel strip, an electro-galvanized layer excellent in bare corrosion resistance and corrosion resistance after chromating; the improvement characterized by: keeping the cobalt content in said electro-galvanizing bath within the range of from 8 to 30 g/l, as converted into metallic cobalt, the chromium content in said electro-galvanizing bath within the range of from 0.1 to 1.5 g/l, as converted into metallic chromium, and the temperature of said electro-galvanizing bath within the range of from 35.degree. to 60.degree. C.; and, flowing said electro-galvanizing bath between said steel strip and said anode plate at a flow velocity of at least 0.35 m/sec in a direction at right angles to the travelling direction of said steel strip.

Process for manufacturing electro-galvanized steel strip

In an acidic zinc sulfate and iron sulfate electro-galvanizing bath, of which a pH value has been adjusted to under 1.5, containing iron from 20 to 90 wt. % relative to the total amount of metals capable of being electro-deposited in said acidic electro-galvanizing bath, a steel sheet is subjected to an electro-galvanizing treatment, with an electric current having a current density of from 10 to 40 A/dm.sup.2 to form on said steel sheet an electro-galvanized layer in a weight of from 1 to 50 g/m.sup.2, containing iron from 5 to 35 wt. % relative to the total weight of the electro-galvanized layer.

Process for manufacturing electro-galvanized steel sheet excellent in

An electro-galvanized steel sheet for coating excellent in bare corrosion resistance, corrosion resistance after coating and formability, which comprises: a steel sheet; a first electro-galvanized layer, as a lower layer, in an amount of from 5 to 120 g/m.sup.2 per side, formed on at least one surface of said steel sheet, said first electro-galvanized layer comprising either an electro-galvanized layer consisting essentially of zinc or a compound electro-galvanized layer consisting essentially of zinc, cobalt and at least one of chromium, indium and zirconium; and a second electro-galvanized layer, as an upper layer, in an amount of from 0.2 to 10 g/m.sup.2 per side, formed on said first electro-galvanized layer, said second electro-galvanized layer consisting essentially of an alloy layer of zinc and from 1 to 60 wt. % iron. Said electro-galvanized steel sheet for coating is adapted to serve particularly for external, underside and closed structures of an automobile.

Dual layer-coated electro-galvanized steel sheet for coating with

A chromated electro-galvanized steel sheet is manufactured by electro-galvanizing a steel sheet in an acidic galvanizing bath containing zinc with or without specified amounts of cobalt, or with specified amounts of cobalt and with at least one of chromium (Cr.sup.+3, Cr.sup.+6 or Cr.sup.+3 and Cr.sup.+6) and zirconium; then electro-galvanizing in a zinc-based galvanizing bath containing specified amounts of at least one of chromium (Cr.sup.+3, Cr.sup.+6 or Cr.sup.+3 and Cr.sup.+6), tin and indium; and chromating the resulting steel sheet.

Chromated electro-galvanized steel sheet excellent in corrosion

In a Zn-ion based acidic galvanizing bath containing at least one additive selected from the group consisting of:

Method for manufacturing an electro-galvanized steel sheet excellent in

In a Zn-ion based acidic galvanizing bath containing one additive selected from the group consisting of:

Growing community of inventors

Fukuyama, Japan

Masaru Ohmura