| 摘要 |
PROBLEM TO BE SOLVED: To provide an organic composite coated steel sheet in which blackening is suppressed while securing needed corrosion resistance by depositing a chromium-free corrosion inhibition film on a galvanized steel sheet subjected to mechanical treatment such as skinpass rolling and roll brush cleaning. SOLUTION: The corrosion inhibition film is the one essentially consisting of a silicic compound and an organic resin, and the area ratio (S) of a new face formed by mechanical treatment and the corrosion resisting capacity (T) evaluated by the area ratio of while rust generated on the surface of the steel sheet after a salt spray test for 72 hr in accordance with JIS Z2371 after the deposition of the film satisfy the following inequality: (1) S<=5Ln(T)+75 (where T>0) or (2) S<=75 (where T=0).
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