Testing methods of catalytic anodes and conventional lead alloys in zinc and copper electrowinning

Abstract

Dimensionally stable anodes (DSAs) or coated titanium anodes are considered for metal electrowinning to replace the conventional lead alloys to insure lower oxygen overpotential ‘OER’, better stability and pure deposits in sulfate solution. Chemical analysis and basic metallographic examination of the DSA alloy are necessary. Scanning electron microscopy and X-ray diffraction are indispensable to examine surface morphology of the DSAs. Open circuit potential measurements in sulphuric acid solution for long periods, and cyclic voltammetry tests to monitor the surface properties of DSA specimens. Potentiodynamic and linear polarisation measurements are interesting to evaluate corrosion rate, active, active–passive and passive behaviours. Galvanostatic study of the DSA simulates the performance in practice. Electrochemical impedance is recommended to study the electrochemical double layer properties and in situ characterisation of the (DSA) oxide layer/electrolyte inter-phase. Sensitivity of the electrochemical noise electrochemical noise technique in situ has been established recently for the detection of spontaneous changes of DSAs during electrowinning. Scanning vibrating electrochemical probe could identify in situ micro localised variation of potential due to passivation or localised corrosion form such as pitting.