| 摘要 |
PROBLEM TO BE SOLVED: To prevent the corrosion by the occurrence of dew condensation in the different member contact sections within a steel house by incorporating silica into chromate films. SOLUTION: The amount of the silica to be added is preferably specified 10 to 100 pts.wt. per 100 pts.wt. of the total weight of chromium. The coating weight of the chromate is preferably 50 to 200 mg/m2 in terms of chromium per unit area of he chromate coating surface. This surface treated steel sheet is <=2 g/m2/year in the corrosion rate of zinc under the environment of <=2×10-3 mgNaCl/day/100 cm2 in the amount of incoming sea salt particles and -10 to 20 deg.CΔT value defined by the following equation.ΔT = steel product temperature ( deg.C) - steel product exposure space dew point ( deg.C). Consequently, the surface treated steel products are sufficient for use under the atm. corrosion atmosphere and the steel house having excellent durability may be obtained by disposing the steel products under the floor and/or within the walls which are the sections where particularly dew condensation occurs.
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