Enhanced pitting corrosion resistance of aluminum alloy 7075 in the presence of oxalate anions
- Univ. of Patras (Greece)
The presence of oxalate in chloride-containing corrosive aqueous media was found to protect aluminum alloy AA 7075 (UNS A95075). The effect of 0.05 M sodium oxalate on induction times for the initiation of pit formation was measured on AA 7075 specimens. The variance and the mean value of the induction times measured increased with the time of specimen immersion at the open circuit potential (OCP). Statistical analysis was done by potentiostatic measurement of several specimens using electrochemical instrumentation controlled by a personal computer. Pit generation rates were found to be inversely proportional to the duration of the immersion period at OCP. Therefore, it was concluded that prolonged exposure of the tested specimens to sodium oxalate solutions enhanced their resistance to corrosion. Impedance measurements confirmed this finding. The increased resistance was attributed to the retardation of the process by which the surface protective layer would have been destroyed. This retardation may have been ascribable to the formation of surface complexes between Al{sup 3+} and oxalates from the bulk solution. Polarization of the specimens at anodic potentials reduced the corrosion resistance of AA 7075, possibly because of the destabilization of the surface complexes formed between Al and the oxalate ions.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 187047
- Journal Information:
- Corrosion, Vol. 51, Issue 1; Other Information: PBD: Jan 1995
- Country of Publication:
- United States
- Language:
- English
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