Corrosion Assessment of a Lead-Based Composite in Sulfuric Acid Electrolytes

In this study, corrosion performances of the Pb-MnO2 composite in a sulfuric acid electrolyte solution at a wide range of anodic potentials were investigated. The protective effects of manganese ions as an additive to the electrolyte were also studied. An industrially supplied PbAg alloy was examined in some cases and the obtained results were used as benchmarks for comparison. Oxidation of these materials and properties of the formed anodic layers were examined using electrochemical techniques including electrochemical impedance spectroscopy, cyclic voltammetry, potentiostatic polarization, and linear sweep voltammetry. Scanning electron microscopy, x-ray diffraction, and Raman spectroscopy were used to characterize the anodic layers. The presence of MnO2 particles in the Pb-MnO2 caused the open-circuit potential of lead to increase from the PbSO4 potential region to the PbO potential region, contributing to different composition of the anodic layer and higher charge transfer resistances of the corrosion layer in comparison with those of the PbAg alloy. The charge transfer resistance of the composite increased with potential within the PbO/PbSO4 potential region. At the PbO2 potential region, the Pb-MnO2 composite anode showed a larger amount of PbO2 in the corrosion layer than the PbAg alloy in the Mn-free electrolyte. The presence of manganese ions inhibited the formation of PbO2 on the anodes, an effect that was more significant on the composite anode. Regardless of the electrolyte composition, the amount of PbO2 corrosion product on the composite anode increased with the polarization time and the applied potential.