Abstract
ADC 12 aluminum alloy die castings and aluminum of 99.87% purity were anodized in sulfuric acid and boric acid/sodium tetraborate solution at constant pulse voltage with an on-time of 25ms and off-tims of 1-1000ms. The electrochemical properties of the barrier layer were examined by measuring changes in ionic current and applied voltage during the off-times of the pulse wave.
In sulfuric acid solution, ionic current densities increased rapidly for ADC 12 and the change in applied voltage decreased exponentially as the off-time of the pulse wave was lengthened. Barrier layers formed on ADC 12 in sulfuric acid solution had better charging properties than those formed in boric acid/sodium tetraborate solution.
Barrier layers formed on ADC 12 in boric acid/sodium tetraborate solution had much poorer charging properties than those formed on 99.87% aluminum.
