METHOD OF TREATING SURFACE CONTROL LIQUID USED FOR PHOSPHATE FILM CHEMICAL CONVERSION TREATMENT

摘要

PROBLEM TO BE SOLVED: To provide a method of treating a surface control liquid which is capable of maintaining the quality of the surface control liquid even without discarding of the deteriorated surface control liquid or renewing of the surface control liquid in phosphate film chemical conversion treatment. SOLUTION: Ultrasonic vibration is applied to the surface control liquid used in a surface treatment process step in the phosphate film chemical conversion treatment so as not to flocculate the colloidal particles thereof, by which the flocculation is prevented and the deterioration of the surface control liquid is obviated and therefore there is no need for discarding the deteriorated surface control liquid or renewing the surface control liquid and the quality of the surface control liquid is maintained.