Nippon Steel Corporation

Sato Hisaaki

Teruaki Izaki

Seijun Higuchi

Makoto Yoshida

Masami Osawa

A method for producing a composite steel strip having a high corrosion resistance comprises electroplating a steel strip substrate in an electroplating bath to codeposit a zinc-based metal matrix and corrosion-preventing fine solid particles. The particles comprise a core which may be, for example, chromate, phosphate, aluminum, molybdenum or titanium compounds and a thin coating membrane which may be, for example, SiO.sub.2, Al.sub.2 O.sub.3, ZrO.sub.2, TiO.sub.2 or a resin encapsulating the core. The core material is soluble in the electroplating bath while the coating membrane is substantially insoluble in the electroplating bath. The electroplating bath also contains an agent for promoting the codeposition of the zinc-based metal matrix and the particles, and may optionally include a number of additional fine particles which may be, for example, SiO.sub.2, TiO.sub.2, Cr.sub.2 O.sub.3, Al.sub.2 O.sub.3, ZrO.sub.2, SnO.sub.2, or Sb.sub.2 O.sub.5.

Method of producing a high corrosion resistant plated composite steel

An electroplated composite steel strip having a high corrosion resistance comprises a steel strip substrate and a corrosion resistant coating layer which comprises at least a base plating layer comprising a zinc-based metal matrix, a number of corrosion-preventing fine solid particles consisting essentially of core fine particles of, for example, chromate, phosphate, aluminum, molybdenum or titanium compounds, and encapsulated by very thin coating membranes consisting of, for example, SiO.sub.2, Al.sub.2 O.sub.3, ZrO.sub.2 or TiO.sub.2, and optionally a number of additional fine particles consisting essentially of, for example, SiO.sub.2, TiO.sub.2, Cr.sub.2 O.sub.3, Al.sub.2 O.sub.3, ZrO.sub.2, SnO.sub.2 or Sb.sub.2 O.sub.5.

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Kitakyushu, Japan

Sato Hisaaki