Evaluation of coated titanium anodes

Coated Titanium Anodes (CTAs) first invented by H. Beer in the 1950s have become standard technology for many electrolysis industries. They consist of precious metal and other oxides coated on a valve metal substrate. As the name suggests, these anodes use titanium as the metal substrate. IrO2 - Ta2O5 binary coatings are used for oxygen evolution systems. In recent years, with increasing concerns about energy consumption in hydrometallurgical processing, there is an ongoing attempt to use these anodes for copper electrowinning. As compared to lead anodes currently used, CTAs reduce the oxygen evolution overpotential, resulting in energy saving. They also eliminate lead sludge giving superior copper cathode deposits. Additionally, the workforce is not exposed to the harmful effects of lead. For this work, anodes with IrO2 - Ta2O5 coatings were prepared in the laboratory having the same total coating loading but varying the number of layers by changing the speed of withdrawal in dip coating. A second set of CTAs were fabricated on niobium, Ti Grade 1, Ti Grade 7 and Ti Grade 36 metal substrates. All the anodes prepared in the laboratory were characterized using standard electrochemical techniques and also subjected to accelerated life testing. Finally the anodes prepared in the laboratory were compared to commercially available industrial anodes. The laboratory produced anodes were found to be superior to the commercial anodes in terms of lifetime per weight of coating loading. This improvement was not the result of the variables examined which had minimal effect on anode performance.