PURPOSE: To form a hot dip galvanizing film excellent in adhesive strength, free from cracks, and colored into brown color by heating a steel sheet hot dip galvanized with molten Zn containing specific amounts of Fe and Mn and then immersing this steel sheet into an acidic aqueous solution containing specific acid and oxidizing agent.
CONSTITUTION: A steel sheet, etc., are hot dip galvanized with molten Zn containing, by weight, 1-15% Fe and 0.05-1% Mn at 430-600°C, preferably 430-480°C, bath temp., by which a plating film free from fine cracks is formed. Subsequently, heating is performed at 440-600°C, preferably 500-550°C, 30 seconds to ten-odd minutes to form the composition of the plating layer into a Zn-Mn-Fe alloy phase, and the above steel sheet is immersed into an acidic aqueous solution which contains acid and oxidizing agent, such as H2SO4 and KMnO4 or HCl or HNO3 and K2Cn2O7, and in which pH value is regulated to 1-3 for several tens seconds to several minutes, by which the plated film can be colored into brown color.
NISHIMURA EIJI
YAMAMOTO YASUNARI
| JPS63247330A | 1988-10-14 | |||
| JP46042007A |