Material problems encountered in anodic MnO2 deposition

The characteristic material problems in electrolytic manganese dioxide (EMD) deposition concern the electrolysis cell components and, especially, the anodes. Temperature, sulphuric acid concentration, and current density are the most critical parameters which determine the corrosion and life times of the lead, graphite or titanium anodes. The corrosion of lead, even under the cover of electrodeposited manganese dioxide, pollutes the technical product. Graphite anodes are slowly oxidized, a process which limits their life time. The behaviour of titatanium as anode material is determined by the conductivities of the TiO x interlayer as well as of the manganese dioxide deposits in the layered system Ti−TiO x MnO2. Passivation and depassivation reactions in conventional EMD electrolysis are described and the improved behaviour of titanium anodes in the suspension bath process is explained.