Transient Relaxations of Ionic Conductance during Growth of Porous Anodic Alumina Films: Electrochemical Impedance Spectroscopy and Current Step Experiments

Simulation-Assisted Process Design and Experimental Verification of Laterally Confined Oxide Areas Generated with Continuous Electrolytic Free Jet on EN AW-7075 Aluminum Alloy

Local anodization with a free electrolyte jet is a suitable solution for locally confined surface functionalization without additionally required preparation of the parts. However, the geometrical formation of the anodic oxide layer in jet-based anodization is not yet sufficiently understood. In this study, numerical calculations based on physical descriptions are used to describe the lateral and vertical oxide formation on aluminum alloy EN AW-7075. The required electrical resistance and capacitance were determined by immersion-based anodization and implemented into the numerical simulation model to evaluate the electrical conductivity of the porous layer. The simulation results showed an electrical conductivity of 2.6 × 10^-6 S/m for the porous layer. Subsequently, a model for jet-based anodization was developed and the previous results were implemented to calculate the oxide formation. The simulation results showed decreasing oxide layer thickness at increasing radial distance from the center of the jet, which corresponds to experimental results. The simulation model was validated by varying the current efficiency from 5% to 90%, where similar developments of the anodic oxide layer thickness compared with experimental results were determined at 5%.