Effects of sulfate and nitrate anions on aluminum corrosion in slightly alkaline solution.

The corrosion mechanisms and kinetics of AA1085 in Li 2 SO 4 and LiNO 3 aqueous rechargeable lithium-ion battery electrolytes were investigated at pH 11 using chronoamperometry. The corrosion kinetics of AA1085 is controlled by the electrolyte concentration level and the anodic potentials. AA1085 is susceptible to crystallographic pitting corrosion in Li 2 SO 4 electrolytes. The rates of pit nucleation and pit growth both decreased at higher Li 2 SO 4 concentrations or at lower anodic potentials. AA1085 passivates against pitting corrosion in LiNO 3 electrolytes due to the formation of a thick, uniform corrosion product layer. The growth rate of the passive film was slightly enhanced by increasing the electrolyte concentration and anodic potentials. X-ray photoelectron spectroscopy spectra showed the formation of a thin sulfate-incorporated passive film on the electrode, which comprises Al 2 (SO) 4 18H 2 O, Al(OH)SO 4 and Al(OH) 3 , before the occurrence of pitting growth in 2 M Li 2 SO 4 electrolyte. The thick corrosion product layer formed in 5 M LiNO 3 electrolyte was composed of Al(OH) 3 and AlOOH. Raman spectroscopy on deionized water, LiOH solution, Li 2 SO 4 and LiNO 3 electrolytes depicted changes of solution structure with increasing electrolyte concentration. The influence of extrinsic and intrinsic factors on the corrosion kinetics of AA1085 in Li 2 SO 4 and LiNO 3 electrolytes at pH 11 are discussed in detail. [ABSTRACT FROM AUTHOR]