EIS investigation of zinc dissolution in aerated sulfate medium. Part I: bulk zinc

The kinetics of anodic dissolution and corrosion of zinc are investigated b y electrochemical impedance spectroscopy in sulfate medium for various surf ace preparation conditions and different experimental procedures. A new ver sion of the reaction model, which was established previously, accounts well for the experimental results. It implies several parallel paths of dissolu tion and three adsorbed intermediates: Zn-ad(+), Zn-ad(2+) and ZnOHad. From the simulation of impedance data are deduced the values of quantities such as the partial current intensities of each parallel paths or the surface c overages by three adsorbates. It is shown that the surface preparation cond itions may affect the balance between the competitive dissolution paths. Wh en zinc is immersed in the electrolyte, a protective layer is formed, which inhibits the direct dissolution of the metal, but which tends to be elimin ated by a potential activation. These phenomena are time dependent and may be affected by the slow formation of a corrosion product layer. (C) 2001 El sevier Science Ltd. All rights reserved.