Electrochemical behavior of anodized Mg alloy AZ91D in chloride containing aqueous solution

Electrochemical behavior in aerated 3.5 wt.% NaCl solution of Mg alloy AZ91D anodized or not has been investigated by using electrochemical impedance spectroscopy, potentiodynamic polarization and E-corr-t curve. Their microstructures before and after corrosion have been examined under scanning electron microscope. Testing results from E-corr-t and polarization curves indicate that the corrosion behavior of Mg alloy makes significant, characteristic changes due to anodization. Impedance spectra obtained show a regular evolution with exposure time revealing the development of corrosion damage. SEM micrographs confirm that there are pores, defects and microcracks in anodic film which determine the existence of film-vulnerable regions. Electrochemical data are combined with micrographs to explain protection mechanism of anodic film and corrosion mechanism of Mg alloy. (c) 2005 Elsevier Ltd. All rights reserved.