AC current perturbation techniques for measurement of corrosion rates

Abstract

It was shown earlier by the authors that the corrosion rate of a metal could be measured by applying a small amplitude sinusoidal AC potential and determining the harmonics present in the resulting current. In this paper, it is demonstrated that the corrosion rate can also be obtained by current- controlled techniques. The first technique consists in applying a current controlled small amplitude AC signal ΔI sin wt, super imposed over DC of sufficient magnitude to keep the system in the Tafel region. The resulting AC and DC potential responses enable the corrosion rate to be determined. In the second method described here, a signal of the from A1 ΔI 10^ΔE.K sin wt is applied to the system through a galvanostat. The resulting sinusoidal AC and DC potential responses are used to determine corrosion rate. Experimental results on the application of these techniques to a system of mild steel in IN sulphuric acid are presented and compared with the results obtained by classical logarithmic polarisation techniques.