The characteristics of oxide films on Al and Al{single bond}1R alloys (R = rare earth metal = Ce, Y) galvanostatically formed (at a current density of 100 μA cm-2) in borate buffer solution (0.5 M H3BO3 + 0.05 M Na2B4O7·10H2O; pH = 7.8) were investigated by means of electrochemical impedance spectroscopy. EIS spectra were interpreted in terms of an "equivalent circuit" that completely illustrate the Al(Al{single bond}1R alloy)/oxide film/electrolyte systems examined. The resistance of the oxide films was found to increase on passing from Al to Al{single bond}1R alloys while the capacitance showed an opposite trend. The stability of the anodic oxide films grown in the borate buffer solution on Al and Al{single bond}1R alloys was investigated by simultaneously measuring the electrode capacitance and resistance at a working frequency of 1 kHz as a function of exposure over a period of time to naturally aerated 0.01 M NaOH solution. Analyses of the electrode capacitance and resistance values indicated a decrease in chemical dissolution rate of the oxide films on passing from Al to Al{single bond}1R alloys.
Influence of rare earth metals on the characteristics of anodic oxide films on aluminium and their dissolution behaviour in NaOH solution
DELSANTE, SIMONA;BORZONE, GABRIELLA;
2010-01-01
Abstract
The characteristics of oxide films on Al and Al{single bond}1R alloys (R = rare earth metal = Ce, Y) galvanostatically formed (at a current density of 100 μA cm-2) in borate buffer solution (0.5 M H3BO3 + 0.05 M Na2B4O7·10H2O; pH = 7.8) were investigated by means of electrochemical impedance spectroscopy. EIS spectra were interpreted in terms of an "equivalent circuit" that completely illustrate the Al(Al{single bond}1R alloy)/oxide film/electrolyte systems examined. The resistance of the oxide films was found to increase on passing from Al to Al{single bond}1R alloys while the capacitance showed an opposite trend. The stability of the anodic oxide films grown in the borate buffer solution on Al and Al{single bond}1R alloys was investigated by simultaneously measuring the electrode capacitance and resistance at a working frequency of 1 kHz as a function of exposure over a period of time to naturally aerated 0.01 M NaOH solution. Analyses of the electrode capacitance and resistance values indicated a decrease in chemical dissolution rate of the oxide films on passing from Al to Al{single bond}1R alloys.
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