The applicability of EIS to determine the optimal polarization potential for impressed current cathodic protection

PurposeThe purpose of this paper is to investigate the application of electrochemical impedance spectroscopy (EIS) as a tool for determining the optimum protection potential (OPP) of brass in impressed current cathodic protection (ICCP) for a given environment.Design/methodology/approachThe electrochemical measurements (EIS, polarization curves) were applied to study the electrode processes of brass in fresh water at different pH values.FindingsThe paper finds that the depolarizer in the electrode process of brass corrosion is different in solutions with different pH values, and has different key steps in the electrode processes. Hence, EIS is a better tool for the determination of the optimum polarization potential for brass in fresh water when the depolarizer of the cathodic half‐cell reaction in corrosion reaction is the dissolved oxygen. However, when the depolarizer in solution is changed, and especially if the reduction reaction of depolarization is not controlled by the mass transport, the EIS method may be not suitable to determine the OPP.Originality/valueThere have been few reports on the effect of pH on the applicability of EIS as a tool for determining the OPP. In this paper, it is clearly shown that the EIS method be suitable only to determine the OPP when the critical step in the electrochemical process is diffusion of the depolarizer. This research can offer theoretical guidelines for the application of EIS to determine the OPP in ICCP.