KINETICS OF THE TRANSFORMATION PROCESS OF PBSO4 TO PBO2 IN A LEAD ANODIC FILM

The kinetics of the nucleation and growth of PbO2 during the potentios tatic oxidation of PbSO4 in a lead anodic film was studied using linea r sweep voltammetry, potential-step and ac impedance tracing methods. The film investigated is the partially reduced anodic PbO2 film formed by. polarizing a lead electrode in 4.5 M H2SO4 solution first at 1.3 V vs. Hg\HgSO4 for 20 min and then at 0.9 V for 5 min. The nucleation and growth process begins some time after the potential step and is co mpleted within 60 s. The pre- and post-nucleation and growth processes correspond to the growth of the anodic film formed by the oxidation o f the lead substrate. The mathematical equations representing the curr ent-time and capacitance-time transients are derived laking the backgr ound oxidation current into account. The experimental results are well fitted by these equations. The process obeys the laws of two-dimensio nal instantaneous nucleation and growth.