Journal of Applied Electrochemistry, Vol.32, No.11, 1269-1278, 2002
Cementation and corrosion at a RDE: Changes in flow and transfer phenomena induced by surface roughness
Cementation and corrosion were investigated in a batch cell to highlight the improvement of the kinetics observed after a certain lapse of time. Experiments on cementation with the Cd(II)/Zn and Ag(I)/Cu systems, and on corrosion with the Ce(IV)/Zn and Cr(VI)/Zn couples, were carried out on a rotating disc electrode immersed in relatively concentrated solutions. Time variations of the concentration of the reacting species and SEM observations showed that the change in reaction kinetics was due to the roughness of the changing surface of the electrode, depending on the chemical system considered. For corrosion, the average roughness was shown to exceed the thickness of the Nernst diffusion layer, and the rougher surface created allows local flow disruption and mass transfer enhancement. Besides, corrosion by Cr(vi) species results in greater roughness of the metal surface with more significant flow disruption than with Ce(IV) at the same concentration.