Discussion and challenges concerning the elaboration of a dissolution reaction mechanism

Abstract

This paper presents a discussion of the particularities and challenges involved in the elaboration of reaction mechanisms. The use of steady state techniques to establish reaction models is critically analysed. Indeed, this paper shows that the same Tafel slope may be associated with different mechanisms; therefore, the Tafel slope cannot be used by itself to determine a specific mechanism with reasonable certainty. Furthermore, a critical analysis of electrochemical methods frequently used to determine corrosion rate, such as the Tafel Slope and LPR, shows the necessity of knowing the mechanisms of reactions beforehand to avoid mistakes in corrosion rate predictions. Reaction mechanisms must be established using both steady state and transient techniques. Finally, in cases where the kinetics are controlled by mass transport, electrohydrodynamic impedance emerges as a very useful tool, whose use is exemplified here by copper electrodissolution in sulphate medium.