A model for galvanostatic anodising of Al in alkaline solutions

In this paper, the modelling of anodic oxide film growth on aluminium in alkaline solutions under galvanostatic conditions is discussed. The material balance of dissolved and adsorbed hydroxyl anion species at the substrate–electrolyte interface is considered, taking into account electrochemical processes of oxide film formation and dissolution via field-assisted and chemical mechanisms associated with evolution of aluminate anions. A differential equation describing the kinetics of oxide film growth under the influence of the above processes is derived and numerically solved. Simulation of the voltage behaviour during oxide film growth, depending on the main electrolysis conditions (such as current density, electrolyte concentration and agitation rate), is performed. Possible reasons for observed discrepancies with experimental data are discussed.