Effect of Longer Waiting Time During OCP and Pre-Applied Cleaning Potential In Corrosion Analysis of Zinc Metal

Tafel analysis is a widely accepted technique for corrosion studies in electrochemistry. A general literature search for one of the electronegative metals, zinc, revealed serious deviations in corrosion results. In order to understand the reasons behind these deviations, zinc metal was investigated at macro and micro levels during and after the Tafel corrosion analysis. In-situ macro surface investigation during the OCP period and Tafel analysis were performed, and it was found that the zinc surface undergoes proceeding corrosion attack following the immersion in 3.5 wt.% NaCl solution. In-situ macro surface analysis exhibited that the pre-oxidation of the surface proceeds as nonuniform at local regions. SEM-EDS and XRD analysis proved that the particular crystal planes of the zinc form ZnO with increasing immersion time. A linear sweep voltammetry (LSV) technique was applied to detect the oxygen removal and starting hydrogen evolution potentials. Three identical Tafel experiments were performed on samples without any treatment, and another three consecutive Tafel experiments were performed on the samples which applied pre-reduction potential. Obtained results revealed that in-situ pre-applied reduction potential just before the Tafel analysis cleaned the surface and allowed uniform oxide formation, resulting in the lowest standard deviation of the calculated Tafel elements.