| 摘要 |
PURPOSE:To obtain a composite Zn plated steel sheet having superior corrosion resistance by coating the surface of a steel sheet with a coating layer formed by dispersing a chromate in a plated Zn alloy layer contg. Fe, Co, Mn or Cr. CONSTITUTION:One side or both sides of a steel sheet are coated with a coating layer formed by dispersing a chromate in a plated Zn alloy layer contg. Fe, Co, Mn or Cr. One or more among SiO2, TiO2, ZrO2 and Cr2O3 may further be dispersed as required. SrCrO4 or BaCrO4 which is slightly soluble in a Zn alloy plating bath is suitable for use as the chromate. Slightly soluble corrosion preventing fine particles of the chromate are dispersed in the Zn alloy plating bath and deposited in the plated Zn alloy layer by cathodic electrolysis. Thus, a composite plated steel sheet having high corrosion resistance and a very low corrosion speed is obtd. Even when the sheet is corroded once, the progress of corrosion is inhibited by the barrier effect of the corrosion product.
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