ACTIVATION OF PASSIVATED TITANIUM ANODES FROM THE ELECTROLYSIS OF MNO2

Titanium anodes with and without a MnO2 precoat were passivated during deposition of electrolytic manganese dioxide and subsequently activated by cathodic reduction. The time dependance of the titanium voltage during passivation and during cathodic reduction was determined by the initial state of the surface. Nonactivated titanium passivated considerably faster than activated titanium with the same thickness of precoat. The application of cathodic currents to passivated anodes caused detachment of the precoat and reduction of the passivating film underneath the precoat. Reduction of the passivating film grown on precoated titanium seems to occur at a much smaller rate than reduction of the film grown on unprecoated titanium.