Gravimetric measurement of oxygen evolution during anodizing of aluminium alloys

A gravimetric method based on changes in buoyancy force of a submerged gas-collecting container has been optimized to measure the evolution of oxygen during anodizing of an aluminium alloy. Previously, the gravimetric method has been used to measure hydrogen evolution from magnesium and aluminium during corrosion processes, either at the free corrosion potential or under relatively low polarization. However, during anodizing, the comparatively higher values of current applied and the heating effects associated with power dissipation might introduce artefacts in the gas measurement. Optimization of the experimental setup enabled reduction or elimination of such artefacts, so that a reliable measurement could be obtained. The results show that typically about 15 to 20% of the current applied to an AA 2024-T3 aluminium alloy during anodizing in sulphuric acid under the present conditions was used in generating oxygen, which is in reasonable agreement with estimates in the literature using less direct methods.