Nippon Steel Corporation

Motoo Kabeya

Yoshio Shindou

Fumio Yamazaki

Katushi Saito

Yoshio Shindo

Takashi Shimazu

Mitsumasa Nagahisa

Teppei Tamura

Hidejirou Asano

The present invention provides a method for producing a highly corrosion resistant organic composite-plated steel sheet which is inhibited from liberation of chromium, which comprises forming a chromate film comprising a composition of the following (A) as a first layer at a coating amount of 5-150 mg/m.sup.2 as a solid film on the surface of a zinc or zinc alloy plated or zinc composite alloy plated steel sheet and then, coating on the first layer an organic solvent coating composition of the following (B) as a second layer at a thickness of 0.3-5 .mu.m as a solid film.

Method of producing organic composite-plated steel sheet

This invention provides an organic multicoated steel sheet susceptible to cationic electrodeposition coating which comprises a zinc or zinc alloy plated steel sheet and as a first layer provided on the surface of said plated steel sheet a sparely soluble chromate film of 1-30% in water soluble matter, 0.01-1.0 in Cr.sup.6+ /Cr.sup.3+ ratio and 10-150 mg/m.sup.2 in total chromium application amount on one surface and as a second layer provided said first layer a solid film having a thickness of 0.3-5 .mu.m of a solvent type coating composition having the following composition based on the weight of non-volatile matter:

Multicoated steel sheet susceptible to cationic electrodeposition coating

This invention provides a highly corrosion-resistant, colored thin film-coated steel sheet having excellent press-processability and spot-weldability, which comprises a plated steel sheet, a first layer of a sparingly soluble chromate film formed on surface(s) of the plated steel sheet and having a water soluble content of 1 to 30%, a Cr.sup.6+ /Cr.sup.3+ ratio of 0.01 to 1.0 and a total chromium build-up of 10 to 150 mg/m.sup.2 on one surface, and a second layer of a 0.3 to 5 .mu. thick solid coating film formed of an organic solvent-type coating composition, the solid coating film being comprised, based on the weight of the nonvolatile content, of

Highly corrosion-resistant, colored thin film-coated steel sheet having

Disclosed is a steel sheet having an organic composite plating layer excellent in press workability, spot weldability, electrodeposition coatability and corrosion resistance which comprises a zinc plated, aluminum plated or zinc base composite alloy plated steel sheet, a first layer of an insoluble chromate film of 5% or less in the content of water-soluble matter formed on the surface of the steel sheet at a coverage of 10-150 mg/m.sup.2 in terms of chromium content and a second layer of a coating composition having the following composition coated at a thickness of 0.3-5 .mu.m as a solid film on said first layer:

Organic composite-plated steel sheet

A Zn-Al hot-dip galvanized coating on a steel sheet may exhibit intergranular corrosion and be degraded due to the Al's secular enrichment in the grain boundaries of coating. This is prevented in accordance with the present invention by the galvanizing bath composition which contains from 0.15 to 10% of Al, from 0.1 to 1% of Sb, from 0.01 to 2% of Si, and the balance being Zn and unavoidable impurities such as Pb, Sn, and Cd in an amount less than 0.02%, and additionally contains at least from 0.01 to 1% of at least one member selected from the group consisting of Mg and mischmetal.

Zn-Al hot-dip galvanized steel sheet having improved resistance against

A Zn-Al hot dip galvanized steel sheet having an improved resistance to secular peeling of a galvanized layer, characterized by a composition of the layer and galvanizing bath which consist of from more than 0.3 wt % to 10 wt % of Al, from 0.2 to 1.0 wt % of Sb, a total of less than 0.02 wt % of impurities including Pb and Sn, and a balance of Zn.

Hot-dip galvanized steel sheet, wherein said coating layer is characterized by being highly resistant to flaking either in a high-temperature humid atmosphere or in long-term indoor aging. The coating comprises 0.1 to less than 0.2 wt % Al, 0.1-0.5 wt % Sb, the remainder being Zn and unavoidable impurities, the total of the unavoidable impurities other than Fe, namely Pb, Cd and Sn being less than 0.02 wt %, the ratio of Sb/Pb being 10-250, and the Al present in the coating layer being in the form of an Al-Sb eutectic.

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Kimitsu, Japan

Motoo Kabeya