Abstract

Oxidation behaviour of aluminium and its alloys in molten NaNO3

Author(s): S.S.Mahmoud, M.M.Ahmed, A.A.Kassab, R.A.El-Kasaby

The oxidation behavior of aluminum and its allays was investigated in molten NaNO3 at 400oC .The techniques of measurements were: open-circuit potential, galvanic current, anodic galvanostatic polarization and electrochemical impedance spectroscopy. The electrodes undergo spontaneous passivation in molten NaNO3 due to the formation of oxide scales on their surface. The thickness of the oxide scales increases with increasing immersion time and also depends on the composition of the electrode. Corrosion tests of the oxide scales formed on the electrodes surface in aqueous HCl solution indicate that these scales dissolve after an induction period with a rate depending on the composition of the electrode. The oxide scales formed during oxidation inmolten NaNO3 under anodic polarization conditions are multilayered. The inner layer of oxide scales is more protective than the outer layer.