中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 19 No. 3 June 2009 |
（1. School of Materials Science and Engineering, South China University of Technology,
Guangzhou 510640, China;
2. School of Science, Foshan University, Foshan 528000, China）
Abstract:In order to accelerate the conversion coating formation on 6063 Al alloy in the Ce(NO3)3 solution, accelerants of chloride and ammonium salt were used. The coating morphology, composition and structure were analyzed with SEM/EDS, EPMA, XPS and XRD. The coating morphology is influenced by the composition, pH value and temperature of the treating solution. The coating composed of metal oxide, metal hydroxide and hydrate appears to be amorphous. The elements in the coating are Al, Ce, O, Mn and Mg, while the Ce element exists in the forms of Ce3+ and Ce4+. The accelerant of chloride can increase the compactness and Ce content of the coating, so the coating corrosion resistance is remarkably improved. A scheme for the electrochemical reaction in the coating formation was proposed, and the potential change in the coating formation was also studied. It is found that chloride can shorten the time period of the first and the second stages in coating formation.
Key words: aluminum alloy; conversion coating; rare-earth element
