Corrosion-resistant surface-coated steel sheet
First Claim
1. A surface-coated steel sheet having improved corrosion resistance, comprising a steel sheet having on at least one surface thereof an inorganic-organic composite coating which comprises the following layers (a) to (d) from bottom to top of the coating:
- (a) a first zinc alloy plating layer with a coating weight of 10-100 g/m2 which contains at least one of nickel (Ni) and cobalt (Co) as an alloying element in an amount satisfying the following inequality;
space="preserve" listing-type="equation">0.05≦
(5×
Co)+Ni≦
10 in weight percent,(b) a second zinc alloy plating layer with a coating weight of 0.05-10 g/m2 which contains at least one of Ni and Co as an alloying element in an amount satisfying the following inequality;
space="preserve" listing-type="equation">10<
(5×
Co)+Ni≦
40 in weight percent,(c) a chromate film layer with a coating weight of 20-300 mg/m2 as Cr, and(d) an organic coating layer, with a thickness of 0.2-5 μ
m.
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Abstract
A surface-coated steel sheet having improved corrosion resistance and suitable for use as automobile inner and outer panels comprises a steel sheet having on at least one surface thereof a composite coating which comprises the following layers (a) to (d) from the bottom to the top of the coating:
(a) a first zinc alloy plating layer with a coating weight of 10-100 g/m2 which contains at least one of Ni and Co in an amount satisfying the following inequality:
0.05≦(5×Co)+Ni≦10 (in weight
percent),
(b) a second zinc alloy plating layer with a coating weight of 0.05-10 g/m2 which contains at least one of Ni and Co in an amount satisfying the following inequality:
10<(5×Co)+Ni≦40 (in weight
percent),
(c) a chromate film layer with a coating weight of 20-300 mg/m2 as Cr, and
(d) an organic coating layer with a thickness of 0.2-5 μm.
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Citations
22 Claims
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1. A surface-coated steel sheet having improved corrosion resistance, comprising a steel sheet having on at least one surface thereof an inorganic-organic composite coating which comprises the following layers (a) to (d) from bottom to top of the coating:
-
(a) a first zinc alloy plating layer with a coating weight of 10-100 g/m2 which contains at least one of nickel (Ni) and cobalt (Co) as an alloying element in an amount satisfying the following inequality;
space="preserve" listing-type="equation">0.05≦
(5×
Co)+Ni≦
10 in weight percent,(b) a second zinc alloy plating layer with a coating weight of 0.05-10 g/m2 which contains at least one of Ni and Co as an alloying element in an amount satisfying the following inequality;
space="preserve" listing-type="equation">10<
(5×
Co)+Ni≦
40 in weight percent,(c) a chromate film layer with a coating weight of 20-300 mg/m2 as Cr, and (d) an organic coating layer, with a thickness of 0.2-5 μ
m. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification