The corrosion of pure magnesium in aerated and deaerated sodium sulphate solutions

The corrosion behaviour of pure magnesium in aerated and deaerated Na2SO4 solutions (0.01 and 0.1 M) was investigated by steady-state current-voltage curves and electrochemical impedance measurements with a rotating disc electrode. It was shown that the anodic current densities were lower and the resistance values higher in deaerated media. It was demonstrated that the absence of HCO3- due to the absence of CO2, which is always present ill the natural environment was responsible for the results observed. The magnesium surface was covered with a porous film (MgO, Mg(OH)(2)) which became thicker with time. The protection afforded by the layer was low and the corrosion rate remained constant as the immersion time increased. In addition, experiments carried out at different NaHCO3 concentrations in deaerated media revealed that the corrosion rate of magnesium was accelerated when the NaHCO3 concentration increased due to dissolution of the film (MgO, Mg(OH)(2)). It was concluded that O-2 did not influence magnesium corrosion. (C) 2001 Elsevier Science Ltd. All rights reserved.