Reaction mechanism for zinc dissolution in chloride electrolytes
Résumé
A model of interfacial processes is developed so as to account for the polarization curves and impedance plots obtained for zinc dissolution in various electrolytes containing ZnCl2 and/or NH4Cl. The slow electrode activation with increasing anodic potential is related to the removal of zinc hydroxide which acts as a protective layer at corrosion potential. The reaction patterns for zinc dissolution involves two parallel paths. The major path is catalysed by the ZnadsI intermediate and the minor path involves a second intermediate such as ZnadsII. The minor path is much more dependent on the volume diffusion of reacting species than the major one. Both paths are strongly stimulated by chlorides anions which appear to be responsible for zinc corrosion.