The electromechanical study on Magnesium sacrificial anode in cathodic protection

Abstract

Magnesium is among the anode material usually applied in cathodic protection in soil application. The corrosion behaviour of Mg anode was studied to understand corrosion behaviour of the Mg anode. The electrochemical polarisation test on the Mg ingot, ascast Mg (99.9 wt% Mg, 0.1wt% Mn) and pure Mg (99.7wt% Mg, 0.2wt% Mn, 0.01wt% Si and 0.047 wt% Fe) were done using potentiostat Gamry G 300. These test were done to obtained polarisation curve and open circuit potential (OCP). The value of open circuit potential of for as cast Mg, Mg ingot and pure Mg are -1.679 V vs. SCE, -1.546 V vs. SCE and -1.709 V vs. SCE respectively. The corrosion rate exhibits the significantly different between Mg anodes. The highest corrosion rate achieved by As-cast Mg anode (25.78 um/year). The corrosion current density of the As-cast Mg revealed the highest value (1.02 A/cm2) compared to Mg ingot and pure Mg. The research found that the different of electrochemical properties were believed resulted by different of alloying elements and processes among these Mg anodes.