Corrosion Rate Estimation from Pseudo-Inductive Electrochemical Impedance Response

Frequency responses exhibiting pseudo-inductive characteristics have been observed when using the electrochemical impedance technique. Controversy exists in interpreting and modeling such responses to obtain corrosion rates even when linearity between input and output is demonstrated. When the system is poorly characterized, kinetic modeling becomes impossible. Making appropriate use of circuit analogues can be an effective method for estimating the charge-transfer resistance and, thus, the corrosion rate for such a system. This approach is demonstrated for the estimation of the corrosion rate of carbon steel in a poorly characterized waste stream from a chemical plant. The pseudo-inductive characteristics in the frequency response are hypothesized to be caused by an adsorbed intermediate in the corrosion mechanism.