Abstract:
This work investigated the effect of Pb2+ concentration and current density on the microstructure of PbO2 coatings. The electrodeposition of PbO2 was conducted in a traditional acidic nitrate solution containing Pb(NO3)2 and NaF. Ti coupons pre-coated with a Sb-doped SnO2 interlayer were used as substrate. At a current density < 40 mA/cm2, a preferential crystallographic orientation of β (301) was observed in the coatings, which exhibited a pebble-shaped morphology. In this current density range, the concentration did not show significant influence on both morphology and phase composition. At a relatively high current density, the PbO2 displayed a dominant β (211) texture and a generally rough surface morphology with a small crystallite size. The morphology is sensitive to the corresponding current density and Pb2+ concentration. At a very high current density of 100 mA/cm2, the morphology of PbO2 was affected substantially by the Pb2+concentration. Flower-like microstructure was observed at 0.1 M Pb2+ concentration. It is suggested that a low current density (or low potential polarization) or a sufficiently high Pb2+ concentration are necessary for forming compact and dense PbO2 deposits. In addition, the average crystallite size decreases with increasing deposition current density within a certain range.
