Transactions of Nonferrous Metals Society of China
JOURNAL OF RAILWAY SCIENCE AND ENGINEERING
|Vol. 18 No. 1 January 2008|
（1. School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics,Beijing 100083, China;2. CRC for Cast Metals Manufacturing, Division of Materials Engineering, School of Engineering,University of Queensland, Brisbane, Qld 4072, Australia）
Abstract:The kinetics of forming process of pulse current anodized film on AZ91D Mg alloy was studied by the voltage—time and thickness—time curves. The surface morphology, structure, elemental constitution and valences of the anodic films were analyzed by SEM, EDS, XPS and XRD respectively. The results show that the film-forming process can be divided into four stages. Formation of a dense layer before sparking is the first stage. Formation of a porous layer accompanied with slight sparking is the second stage. The third stage is characterized by fast growth of the porous layer accompanied with more intensive sparking. The fourth stage starts after the sparking process becomes even more vigorous and the pores become large.
Key words: Mg alloy; pulse anodizing; film-forming process