Functional pressure-sensitive adhesive tapes for local anodization of aluminium surfaces

A novel, pressure-sensitive adhesive tape for local anodization of aluminium surfaces was developed. The main difference between this tape anodization and conventional bath anodization is the viscosity of the anodization medium. While the viscosity of industrial anodization baths is similar to that of water, the viscosity of the adhesive matrix is higher by six orders of magnitude. To achieve a reliable application of tape anodization, the differences between bath and tape anodization were examined. This included the impact of process parameters on the morphology of anodic oxide layers. A decrease in the speed of the transport processes in the liquid phase because of the higher viscosity leads to changed rates of growth and the dissolution of the anodic oxide layer. The morphology of anodic oxide layers formed under conditions of high viscosity is presented. Layer thickness, pore density and pore area were obtained by statistical analysis of SEM images. The results are complemented by current-time response measurements during the anodization process. Practical tests of the applicability of the anodization tape for local pre-treatment of aluminium surfaces prior to bonding or painting were successfully performed.