Abstract: The aim of the present invention is to provide a phosphate treated zinc coated steel sheet with excellent workability. A steel sheet coated with a zinc based alloy has a phosphate treated coating on the surface thereof. The phosphate treated coating comprises mainly granulated crystals, specifically, crystals in which the average ratio of the major axis to the minor axis is not less than 1.00 and not more than 2.90. Moreover, the method for producing the phosphate treated coating uses a phosphate treatment solution in which the amount of Mg ions is ≧6 g/l and the amount of Zn ions is ≧0.5 g/l, or a phosphate treatment solution in which the amount of Mg ions is ≧10 g/l, the amount of Zn ions is 0≦ and <0.5 g/l, and the amount of nitric acid ions is ≧40 g/l.

Abstract: The present invention aims at provision of an organic composite galvanized steel sheet having its characteristics such as corrosion resistance and workability improved. Thus, the present invention provides an organic composite galvanized steel sheet that is formed by sequentially depositing on a surface of a steel sheet a galvanization layer, a zinc phosphate layer containing Mg, and an organic layer, and is characterized in that a value of Mg/P (weight ratio) in the zinc phosphate layer is 0.15 or larger and an amount of Mg contained in the zinc phosphate layer is 20 mg/m2 or more. Preferably, the zinc phosphate layer contains one or two or more of Ni, Mn, Co, Fe, Cu, Al, and Ca. In one preferred embodiment, the organic layer is formed as a composite layer containing an organic resin and one or two kinds or more of powder or colloid selected from SiO2, Al2O3, MgO, Fe2O3, Fe3O4, ZrO2, TiO2, and SnO2.

Abstract: A galvanized steel plate for use in a vehicle body, having corrosion resistance and workability that are well-balanced and being suitable for outer plates of a vehicle body is provided. The plate includes a galvanized steel plate having a zinc coating plated on both surfaces thereof; a zinc phosphate coating layer formed on one of the surfaces of the plate that serves as an outer surface of a vehicle body; and a phosphate-containing composite coating formed on the other of the surfaces that serves as an inner surface of a vehicle body, the composite coating being composed of a zinc phosphate coating layer and a phosphate coating containing Mg. The phosphate-containing composite coating preferably contains 2 wt % or more of Mg, and is preferably applied in an amount greater than or equal to 0.5 g/m2.