AC-electrochemical cleaning of aluminum

The effect of AC-electrochemical cleaning on rolled AA1050 and AA5182 is investigated in sulphuric and phosphoric acid under constant AC-current conditions. Potential response and oxide thickness measurements demonstrate the difference between AC-cleaning and AC-anodizing. The roles of the anodic and cathodic charge cycles in creating the cleaned surface features are studied. For AA1050 no contribution of the cathodic hydrogen evolution reaction is witnessed, while for AA5182 an extra metal loss due to the reduction process is apparent. The cleaned surface is covered with a thin oxide layer (<20 nm). Scanning electron micrographs show a rough and cratered surface after AC-cleaning in phosphoric acid. The surface roughening is less severe in sulphuric acid. No etchfilm formation is observed; the oxidized aluminum is removed from the substrate into the solution. The AC-cleaning is more efficient in terms of metal loss (10 or 100 times faster in respectively sulphuric and phosphoric acid) than the traditional acid etching.