Phosphate-treated galvanized steel sheet having excellent resistance to corrosion and blackening

A technology of galvanized steel sheet and corrosion resistance, applied in the field of phosphate-treated galvanized steel sheet, can solve the problems of high manufacturing cost, surface blackening, darkening of the color of zinc phosphate film, etc.

Active Publication Date: 2007-11-07
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] However, both of these techniques require application of a water-soluble solution and heating and baking in the process of forming the uppermost layer of the film. This has the following economical problems. , also requires new coating equipment for coating these coating solutions, leading to high manufacturing costs
[0011] However, in this technology, the zinc phosphate film contains a large amount of Mg, so when exposed to a high-temperature and high-humidity environment, the surface turns black and the blackening resistance deteriorates. At the same time, the zinc phosphate film contained in a high concentration Ni, Co, Cu, so there is a problem that the color tone of the zinc phosphate film becomes dark

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0036] A test plate with a size of 210×100 mm was taken from a cold-rolled steel plate with a plate thickness of 1.0 mm. These test panels were pretreated first. The pretreatment is in the alkaline degreasing solution (liquid temperature: 70°C) added with sodium orthosilicate (60g / L), using a stainless steel plate as a counter electrode, and the current density: 5A / dm 2 , electrolytic degreasing for 30 seconds, water washing after electrolytic degreasing, then immersing in 30 g / L sulfuric acid aqueous solution (liquid temperature: 30° C.) for 5 seconds, pickling, and water washing treatment. After implementing the pretreatment, the test panel is electro-galvanized, and the adhesion amount is 5-40g / m2 on one side of the test panel. 2 galvanized layer.

[0037] The electrogalvanizing treatment is performed as follows.

[0038] A galvanizing bath to which 440 g / L of zinc sulfate heptahydrate was added was used as a galvanizing bath. Add sulfuric acid to adjust the pH of the g...

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Abstract

Disclosed is a phosphate-treated galvanized steel sheet wherein a zinc plating layer is formed on a steel sheet surface, a phosphate treatment layer is formed on the zinc plating layer, and an Ni adhesion portion is interposed between the zinc plating layer and the phosphate treatment layer in an amount of 0.1-500 mg/m<2>. This phosphate-treated galvanized steel sheet is excellent in corrosion resistance and blackening resistance. The phosphate treatment layer may preferably contain not less than 0.1% by mass but less than 2.0% by mass of Mg.

Description

technical field [0001] The present invention relates to a surface-treated steel sheet suitable for use in building materials, home appliances, etc., and particularly to a phosphate-treated galvanized steel sheet suitable as a base steel sheet for painting. Background technique [0002] For parts requiring corrosion resistance in applications such as building materials and home appliances, galvanized steel sheets with surface treatments such as galvanized or galvanized alloys are generally used. These galvanized steel sheets are rarely used directly, and are usually used after coating. When painting, chemical conversion treatment such as phosphate treatment or chromate treatment is generally performed as a pretreatment. [0003] Phosphate treatment is a treatment in which an acidic solution containing phosphate ions is brought into contact with a galvanized steel sheet and reacted to form a crystalline film mainly composed of zinc phosphate on the surface of the coating to i...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23C22/78C23C28/00C23C22/12
CPCC23C22/12C23C28/3225C23C2/26C23C22/07C23C22/78C23C28/321C25D5/48C23C28/322C23C28/345C23C28/00
Inventor 中丸裕树多田千代子山下和美屉冈英男加藤千昭
Owner JFE STEEL CORP
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