Study of colored anodized aluminum with calcon in sulfuric acidic solution using cyclic voltammetry and impedance measurement methods

The effect of coloring condition of Al with Calcon (sodium 2,2'‐dihydroxy‐azonaphthalene‐4‐sulfonate), on the corrosion resistance of Al in 0.1 M sulfuric acid solution was studied, using cyclic voltammetry and measurement of impedance noise methods. The changes in the corrosion resistance of colored aluminum electrodes were evaluated by measuring the magnitude of impedance and cyclic voltammetric responses of anodized and colored electrodes. An irreversible corrosion response was observed at the cyclic voltammogram of the colored aluminum electrode. The current and threshold potential of corrosion responses strongly depends on the applied conditions during anodizing, coloring and sealing stages. In addition, significant changes in impedance at the ac voltammogram and noise level at some ac frequencies were observed, when the electrodes were colored under various conditions. In this regard, the surface of the electrode was studied by Scanning Electron Microscopy (SEM). Comparison of SEM images of the colored and uncolored aluminum specimens showed that the colored surface contained a significant numbers of pits. The results indicated that coloring aluminum with Calcon could reduce corrosion resistance of aluminum and increase roughness of the oxide film.     

Prozess zur Anodisierung von Aluminiumbändern mit hoher elektrischer Durchschlagsspannung

Process for anodizing of aluminum stripes with high electrical breakdown voltage The Aim of the research was to develop an anodizing process for generating a high breakdown voltage on aluminum stripes in the shortest processing time possible. In order to vary process parameters in a wide range, a flexible discontinuous anodizing laboratory device was designed in cooperation with Steinert Elektromagnetbau GmbH Köln. By means of the liquid contact method, conditions equal to non‐solid contact anodizing of aluminum stripes in continuous laboratory devices were simulated. The research was focused on the development of the current pulse shape. The results show that the highest possible breakdown voltages can be achieved in a short processing time using suitable electrical parameters (current pulse shape) and the appropriate post‐treatment. The films generated by the new technology (current pulse shape referred to as “TUCAL”) reveal a higher pore density than conventional layers. This results in a higher ductility (less tendency for cracking).