DEACTIVATION MECHANISMS OF OXYGEN-EVOLVING ANODES AT HIGH-CURRENT DENSITIES

Observed deactivation mechanisms of oxygen evolving DSAs(R) in strongly acidic, sulphate-based electrolytes have been described and separated into classes, in order to clarify the reasons of their occurrence as a function of operating conditions. Laboratory tests (particularly accelerated life tests) are briefly illustrated; they have been intensively used for the identification of experimental conditions, able to affect the catalytic activity and electrode stability. Other deactivation mechanisms and their combinations, usually observed on industrial electrolytic processes (main use of these electrodes is in fast electrogalvanizing plants, operating at high current densities), are described and commented on the basis of laboratory tests, the goal being a general understanding of deactivation mechanisms, and their connection with industrial operating conditions. The resulting scheme has been very helpful to obtain modified electrocatalytic coating and electrode structures, able to operate for long time with good and stable performances.