VOLTAMMETRIC RESPONSE OF ZINC IN SODIUM-HYDROXIDE SOLUTIONS CONTAINING SODIUM SULFIDE

The voltammetric response of Zn in NaOH solutions containing different Na2S concentrations showed that for potentials located between the be ginning of Zn anodic oxidation and Zn passivation, ZnS formation can b e observed as a result of an initial competitive adsorption between OH - and sulphide ions for Zn sites. The anodic layer on Zn in alkaline s olution changes from a ZnS layer at high Na2S concentration to a ZnO/Z n(OH)2 layer in Na2S-free solution. A complex layer, probably involvin g a defective ZnS layer with ZnO domains is produced within a certain OH-/sulphide ion concentration ratio range in the solution. The stabil ity of these layers depends on the applied potential.