PROCESS FOR THE PHOSPHATE CHEMICAL CONVERSION TREATMENT OF A STEEL MATERIAL

摘要

PROCESS FOR THE PHOSPHATE CHEMICAL CONVERSION TREATMENT OF A STEEL MATERIAL A corrosion-resistant phosphate chemical conversion coating layer is formed on a steel material surface by a process comprising bringing the steel material into contact with a treatment liquid containing mixed anions consisting of phosphate ions and at least one other type of active anions, at least one type of metal ions, and an oxidizing agent, to provide a phosphate chemical conversion coating layer on the surface of the steel material, wherein the ratio (P/An) in weight of the phosphate ions (P) to the total of mixed anions (An) is 1/2 or less and the temperature of the treatment liquid is maintained at a level of 40.degree.C or less without external heating.