Technical Note: Distribution of Initial Current Between Bare and Filmed Surfaces: What Is Being Measured in a Scratched Electrode Test? Available to Purchase

To aid in understanding the contribution of the large filmed surface to the measured initial current transient in a scratched electrode test, an in situ fracture technique was used to determine the distribution of currents between the bare and filmed surfaces following the sudden introduction of the bare surface under potentiostatic control. Measurements were made on a 304 stainless steel in deaerated 3.5 percent NaCl solution at room temperature and showed strong influence of the filmed surface on the measured initial current transient. The results support the earlier conclusion that the bare-surface current densities and repassivation kinetics in the literature, based on scratched electrode measurements, are significantly overstated and need to be re-examined.