Abstract Zinc-coated steel materials in general use which have undergone the chromate treatment for improved corrosion resistance suffer from a disadvantage that the corrosion-resistant coating is susceptible to flexure and cracks or peels off at flexures, with the result that the protective function of chromate is lost. The improved corrosion-resistant double-coated steel material to which the present invention relates is obtained by coating in a fusion-bonded state tin or tin-based alloy onto a zinc coating applied to the surface of steel material or by applying a zinc coating on the surface of steel material and further applying in a fusion-bonded state a coating of tin or a tin-based alloy. Thus obtained double-coating free from defects which chromate has, increases in mechanical strength and improves corrosion resistance to an unexpected extent.
IN STEEL MATERIALS HAVING CORROSION-RESISTANT DOUBLE COATING CONSISTING OF INNER AND OUTER TWO LAYERS, AN IMPROVED CORROSION-RESISTANT DOUBLE-COATED STEEL MATERIAL CHARACTERIZED IN THAT SAID INNER LAYER IS A ZINC COATING AND SAID OUTER LAYER IS A TIN-PREDOMINANT COATING FORMED IN A FUSION-BONDED STATE ON SAID INNER LAYER.
Claim 2
Dependent Claim
47 words
IN STEEL MATERIALS HAVING CORROSION-RESISTANT DOUBLE COATING CONSISTING OF INNER AND OUTER TWO LAYERS, AN IMPROVED CORROSION-RESISTANT DOUBLE-COATED STEEL MATERIAL CHARACTERIZED IN THAT SAID INNER LAYER IS A ZINC COATING AND SAID OUTER LAYER IS A TIN-PREDOMINANT COATING FORMED IN A FUSION-BONDED STATE ON SAID INNER LAYER.
Claim 3
Dependent Claim
21 words
An improved corrosion-resistant double-coated steel material in accordance with claim 1 in which the tin-predominant outer coating consists of tin alone.
Claim 4
Dependent Claim
22 words
An improved corrosion-resistant double-coated steel material in accordance with claim 1 in which the tin-predominant outer coating consists of a tin-based alloy.