Effects of scan rate on the potentiodynamic polarization curve obtained to determine the Tafel slopes and corrosion current density

Effects of charging current on the potentiodynamic polarization curve that is obtained to determine the Tafel slopes and corrosion current density are reported in this paper. The potentiodynamic polarization curves are obtained at different scan rates for Ti6Al4V in naturally aerated 3.5% NaCl solution. The results show that the potential where the external current density equals to zero does not equal to the open circuit potential. The extent of the distortion of the polarization curve can be reflected the difference between the two potentials. Some significant errors are introduced into the values of the corrosion current density and Tafel slopes due to this distortion. In addition, severe distortion of the polarization curve can lead to misunderstanding of the electrode process. A new method is adopted to eliminate this distortion, and the potential-dependent of charging current density can also be obtained. (C) 2008 Elsevier Ltd. All rights reserved.