HOT DIP GALVBANIZED STEEL SHEET HAVING SUPERIOR BLACKENING AND SCRATCH RESISTANCE AND SUPERIOR SUITABILITY TO CHEMICAL CONVERSION TREATMENT AND ITS MANUFACTURE

摘要

PURPOSE:To provide superior blackening and scratch resistances and superior suitability to chemical conversion treatment to a hot dip galvanized steel sheet or a steel sheet coated with a Zn-Al alloy by hot dipping by depositing an Ni-P alloy layer having a specified ratio in the composition on the surface of the steel sheet to a specified thickness. CONSTITUTION:A hot dip galvanized steel sheet or a steel sheet coated with a Zn-Al alloy by hot dipping is treated with a soln. contg. Ni ions and phosphate ions to deposit an Ni-P alloy layer having 0.01-0.2 ratio of P/(Ni+P) on the surface of the steel sheet by 0.1-20mg/m<2>.