Corrosion behavior of biomedical AZ91 magnesium alloy in simulated body fluids
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englong Liu Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong, People’s Republic of China
Xinmeng Zhang State Key Laboratory of Welding Production Technology, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Guoyi Tanga) Advanced Materials Institute, Tsinghua University, Shenzhen Graduate School, Shenzhen 518055, People’s Republic of China
Xiubo Tian State Key Laboratory of Welding Production Technology, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Paul K. Chub) Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong, People’s Republic of China (Received 13 February 2007; accepted 29 March 2007)
Fast degradation rates in the physiological environment constitute the main limitation for magnesium alloys used in biodegradable hard tissue implants. In this work, the corrosion behavior of AZ91 magnesium alloy in simulated body fluids (SBF) was systematically investigated to determine its performance in a physiological environment. The influence of the main constituent phases on the corrosion behavior was studied by in situ visual observation and scanning electron microscopy. Energy dispersive x-ray spectrometry and Fourier transfer infrared spectroscopy revealed that both calcium and magnesium phosphates are present in the corroded products besides magnesium oxide. Electrochemical methods including open circuit potential evolution and electrochemical impedance spectroscopy were used to investigate the mechanism. The corresponding electrode controlled processes and evolution of the corrosion products layer were discussed. The degradation rate after immersion in SBF for seven days was calculated from both the weight loss and hydrogen evolution methods.
I. INTRODUCTION
Because of their high strength, ductility, and good corrosion resistance, metallic materials such as stainless steels, cobalt-based alloys, and titanium alloys constitute an important class of materials for hard tissue replacements, especially load-bearing implants. However, because these materials do not degrade spontaneously after implantation into the human body, a second surgical pro-
Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/JMR.2007.0233 2004 J. Mater. Res., Vol. 22, No. 7, Jul 2007 http://journals.cambridge.org Downloaded: 09 Sep 2014
cedure may be necessary after the tissues have healed. Repeated surgeries increase the costs as well as patient morbidity. In addition, mismatch of the elastic moduli between metallic biomaterials and natural bone results in stress shielding effects that can lead to reduced new bone growth.1 In this respect, biodegradable magnesium-based alloys have potential applications, and good biocompatibility has in fact been observed in clinical and in vivo and in vitro assessments.2–4 Unfortunately, pure magnesium and its alloys corrode too quickly at t
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