Cathodic Corrosion of Zinc under Potentiostatic Conditions in NaCl Solutions

Abstract

Zinc electrodes were polarized cathodically at moderate overpotentials in NaCl 0.6 M solutions under potentiostatic conditions for 7 to 17 hours at room temperature. Corrosion products were characterized by using optical microscopy, XRD, Raman microscopy, XPS, and FIB-SEM. Close to the open-circuit potential, the corrosion products were formed by simonkolleite and the electrochemical response exhibits anodic features. At more negative potentials, the current density remains cathodic throughout the polarization and the deposits on the electrode surface consist almost solely of ZnO. The soluble zinc species necessary for ZnO deposition originate from localized dissolution of the substrate in the form of pits. This effect is assigned to the strong alkalinization of the surface due to oxygen reduction. Despite developing greater surface area than bare zinc substrates, the nanostructured ZnO deposits reduced the cathodic activity.[a] Dr.

Oxygen Reduction Investigation on Sputtered ZnO Layers with Nano‐granular Structure

“…The Raman spectral signature (Figure 2b) corresponds to zinc oxide with two major signals near 560 cm À 1 and 430-440 cm À 1 that are in good agreement with previous corrosion studies. [20,21] Those signals are attributed to the A1(LO) mode and to the E2H mode respectively. [39][40][41][42][43] The intensity ratio E2H/ A1(LO) shows that a significant part of the ZnO film is in amorphous state.…”

“…[13][14][15]17] In contrast, on thicker ZnO films (ca. [20,21] They were found to diminish the cathodic activity compared to that of bare zinc in near-neutral solutions. [18,19] Furthermore, the ORR inhibition properties of ZnO (or ZnOcontaining) patinas have been reported in the literature.…”

“…Thin nanostructured ZnO layers with no preferred orientation were grown on zinc, both anodically and cathodically in NaCl electrolyte. [20,21] They were found to diminish the cathodic activity compared to that of bare zinc in near-neutral solutions. ORR activity reduction on steel substrate was also evidenced by Thébault et al while investigating ZnO deposits at the cut-edge of galvanized steel samples using the electrochemical microcapillary cell technique.…”

Impedance Spectroscopy Analysis of Structural Defects in Sputtered ZnO Films

“…The global in situ information provided by EIS was completed by the local ex situ structural data at the nanoscale and microscale obtained with top‐view and cross‐sectional electron microscopy images. In the past years, some reports have demonstrated the benefits of cross‐sectional analysis (with focus ion beam or scanning transmission electron microscopy) in order to gain valuable insight on the effect of the microstructure on the protective properties of ZnO …”

“…A negative polarization was applied to the sputtered ZnO electrodes since the present study was carried out in the context of the investigation of the cathodic properties of ZnO . The cathodic activity of ZnO is still debated in the literature, as reminded by Cole in a recent review on zinc corrosion . A previous work of our group presented the electrokinetic properties of sputtered ZnO layers towards oxygen reduction …”