PRETREATMENT METHOD BEFORE COATING USEABLE IN PREFERABLE CHEMICAL CONVERSION TREATMENT OF METAL

摘要

PURPOSE: Provided is a pretreatment method of metal for coating to ensure preferable chemical conversion treatment thereof without surface control and reduced load to environment. CONSTITUTION: The pretreatment method comprises the step of: treating a subject to be coated using specific chemical agent; and then forming chemical conversion film over the subject. The chemical agent comprises (i) at least one metal selected from zirconium, titanium and hafnium; (ii) fluorine; and (iii) at least one compound selected from amino group containing silane coupling agent, hydrolyzed compound and polymer thereof. The compound(iii) is contained in amount of 5 to 5000ppm in terms of solid content. The chemical agent may further contain at least one specified promoter in amount of 1-5000ppm.