SURFACE TREATMENT OF ZINC OR ZINC ALLOY PLATED STEEL MATERIAL

摘要

PURPOSE:To improve the resistance of a Zn or Zn alloy plated steel sheet to leaving of fingerprints and the adhesion to paint by forming a chromate film contg. aq. colloidal silica and antimonyl pentoxide colloid on the plated surface of the steel sheet. CONSTITUTION:A steel material is plated with Zn or a Zn alloy and the chro mate film contg. a mixture of antimony pentoxide (Sb2O5) colloid with aq. colloidal silica (SiO2) of 40-100mum average particle size is formed on the plated surface. The chromate film satisfies 0.2-5 weight ratio of (Sb2O5+SiO2)/CrO3 (all Cr in the chromate film is expressed in terms of CrO3) and 0.2-15 weight ratio of Sb2O5/SiO2.