Corrosion and anodic behaviors of pure aluminum in a novel alkaline electrolyte

The corrosion and anodic dissolution behaviors of pure aluminum in Na2SnO3-containing 4 mol . L-1 KOH methanol-water mixed solutions with a methanol/water volume ratio of 4:1 were investigated. This was carried out by means of hydrogen collection, polarization curve, galvanostatic discharge, scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). The experimental results indicated that the addition of stannate inhibited the corrosion of aluminum in the 4 mol . L-1 KOH methanol-water solutions by the deposition of tin with a higher hydrogen evolution overpotential on the electrode surface. In the electrolytes with higher stannate contents the inhibiting effect decreased because of the occurrence of some cracks on the tin deposition film. The results of galvanostatic discharge showed that the discharge of aluminum in the Na2SnO3-containing 4 mol . L-1 KOH methanol-water solutions were obviously improved. In addition, the improvement effect enhanced with the increase of stannate content. It was noted that the aluminum anode showed a very flat discharge plateau at relatively low potentials in the electrolyte with 10.0 mmol . L-1 Na2SnO3 at 20 mA . cm(-2) discharge current density.