| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To prevent deterioration in corrosion resistance after coating and adhesion of coating observed when coating a galvanized steel material which has been processed using water-soluble processing oil containing a fatty acid, typically an electric resistance welded steel tube produced from a galvanized steel sheet. <P>SOLUTION: Before coating, treatment for removing a surface layer of a galvanized film is performed by performing cleaning and water washing using an alkaline liquid with pH of 9.5-10.5 and/or performing cleaning and water washing using an acidic liquid with pH of 6.0 or less. Owing to the treatment, Zn, C, and O which exist in the surface layer within a depth of 60 nm of the plated film of the steel material, in terms of an SiO<SB POS="POST">2</SB>reference plate satisfy the following: [O/Zn cumulative average atomic ratio]≥1.15×[C/Zn cumulative average atomic ratio] or [O/Zn cumulative average atomic ratio]≤0.40×[C/Zn cumulative average atomic ratio]. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
