Corrosion estimates from the transient response to a potential step

A numerical method is developed which allows electrochemical estimates of the corrosion rate to be made in experimental circumstances in which the application of conventional methods yields erroneous values. The method is especially suitable with systems that respond very slowly to an applied electrical stimulus, like when the corroding electrode presents very high capacitance values. The polarisation resistance (and corrosion rate) is determined from the current transient response to the application of a potential step. A computational algorithm for fitting the kinetic parameters of the corrosion model to the experimental transient current data series is described. The properties of the proposed method are discussed on the basis of the results obtained from numerical experiments and laboratory tests. Special attention is paid to the typical case of rusted steel specimens.