Use of electrochemical impedance spectroscopy to Study corrosion of galvanised steel in 0.6M NaCl solution

The corrosion mechanism of commercially galvanised steel ( containing Pb) in sodium chloride solution was evaluated using electrochemical impedance spectroscopy and polarisation curves. The behaviour of the system was simulated by an equivalent circuit with two time constants, including a Warburg element to consider the diffusion process at longer immersion times. To begin with, the impedance measurements indicated a non-stationary system with two time constants which could be related to the charge transfer resistance and the adsorption of the intermediate species. With increasing immersion time, the impedance spectra showed a corrosion mechanism that is under activation control. With immersion times of up to one month, the influence of diffusion processes on the overall corrosion mechanism increases significantly.