Ma. Pechcanul et S. Turgoose, THE ELECTROCHEMICAL IMPEDANCE RESPONSE OF FILM-COVERED MILD-STEEL IN NEUTRAL AERATED SOLUTIONS, Corrosion science, 35(5-8), 1993, pp. 1445-1454
Electrochemical Impedance Spectroscopy (EIS) has been widely used in t
he study of corrosion processes and data interpretation is often via s
imple equivalent circuits. However, such circuits often can not be use
d to model real EIS data obtained with film covered or corroded steel
electrodes in near-neutral solutions, especially when interrelation be
tween the various components of the equivalent circuit is allowed for.
Electrochemical impedance spectra have been obtained at the corrosion
potential for a mild steel rotating disc electrode (RDE) in chloride
solutions with addition of zinc-polyphosphate inhibitor, which show cl
ear evidence of mass transport through a porous layer. In addition, d.
c. measurements show very low values of the steady state diffusion cu
rrent, a significant effect of rotation speed of the RDE on the anodic
reaction and evidence that the layer properties depend on the stirrin
g conditions. Analysis of the impedance spectra with a general model p
reviously proposed provides evidence that due to film-limited mass tra
nsfer the anodic reaction becomes reversible.