HIGHLY CORROSION-RESISTANT, DOUBLE-COATED STEEL SHEET EXCELLENT IN COATABILITY AND PREVENTED FROM BLISTERING IN ELECRODEPOSITION COATING AND PROCESS FOR PRODUCING THE SAME.

摘要

A double-coated steel sheet having a zinc-base coating containing at least a zinc alloy coating or a zinc composite coating and having a coating weight of 25 g/m<2> or above, formed on a steel sheet, and an iron-base coating containing at least an iron coating or an iron alloy coating of an iron content of 50 % or above and having a coating weight of 1 to 10 g/m<2>, formed on the zinc-base coating, wherein the total hydrogen occlusion of the coating and the steel is limited to 300 ml/m<2> or below (per sheet face). This sheet has such an excellent coatability that it is prevented from both cratering and blistering in electrodeposition coating and is especially suitable as a rust-preventive steel sheet for automobiles. This steel sheet is produced by applying the aforementioned double-coating on a steel sheet and heat-treating the coated sheet at 100 to 400 DEG C.