The effects of surface treatment and stannate as an electrolyte additive on the corrosion and electrochemical performances of pure aluminum in an alkaline methanol-water solution

Pure aluminum electrodes were treated in alkaline stannate solutions, and the effects of some factors such as NaOH content and treating time were explored. The corrosion and electrochemical performances of the modified aluminum anodes in 4.0 M KOH methanol-water mixed solutions containing a methanol/water volume ratio of 7:3 (30% water) with and without stannate were investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). Metallic tin with high hydrogen evolution overpotential was deposited in aluminum surfaces by the modification treatments using stannate, resulting in the relatively low corrosion rate and markedly enhanced discharge performance of the modified aluminum anodes. In our experimental range the aluminum electrode treated in the solution with 0.1 M NaOH for 30 min showed lower corrosion rate and better discharge performance. The addition of Na2SnO3 in 4.0 M KOH methanol-water mixed solutions with 30% water inhibited the corrosion of the aluminum electrodes modified in the treating solution with 0.1 M NaOH for 30 min, resulting from the deposition of tin with high hydrogen evolution overpotential in aluminum surfaces. The deposition of metallic tin on the electrode surface and the existence of stannate in the electrolytes were responsible for the notable enhancement in the discharge performance of the modified aluminum anode. (C) 2010 Elsevier B.V. All rights reserved.