Effect of small addition of aluminium on electrochemical corrosion behaviour of magnesium-calcium sacrificial anode in underground environment

Abstract

The effect of small addition of Al on the electrochemical performances was investigated by open circuit potential and Tafel Extrapolation method. The results show that open circuit potential reveals as-cast Mg containing Ca alloys with minor content of Al maintained highly negative potential with the range of -1.68 to -1.63VSCE in comparison to both pure Mg (-1.60VSCE) and commercial high potential Mg anode (-1.59VSCE). The result shows the potential was shifted to be more positive with increasing of Al content. Corrosion rate for the as-cast samples remains higher (30 - 17 mpy) than pure Mg (3 mpy) and commercial high potential Mg anode (14 mpy). The increasing small content of Al results in the reduction of corrosion rate significantly. Therefore, its proves that the performance of Mg containing Ca alloy is strongly influenced by the concentration of Al.