Formulation of a criterion predicting the development of uniform regular and non-uniform abnormal porous anodic alumina coatings and revealing the mechanisms of their appearance and progress

A transport analysis criterion, predicting the conditions of uniform regular and non-uniform abnormal oxide growth and verified by different experimental methods, was discovered. As shown, the partial derivative of electrolyte concentration at pore bases to current density at the initial stages of anodization is the decisive parameter; when ∂ C a,b/∂ j0 the oxide growth becomes necessarily regular and abnormal respectively. By this criterion the mechanisms of regular and abnormal development of oxide were also successfully revealed. Their knowledge is important since methods may be developed to produce uniform thick films even in conditions where otherwise non-uniform films are formed.