Influence of anodizing concentration and electric potential on surface morphology and corrosion behavior of anodized magnesium in seawater activated battery

Magnesium is one of the newly developed anode materials for seawater activated batteries. Anodizing is usually performed to expand the surface of anode materials which can improve the battery discharge performance. This work used Oxalic acid with concentration varied from 0.1 to 0.3 as an anodizing agent with electric potential varied from 1.5 to 6.0 Volt for an anodizing process. Electric potential used in the anodizing was varied from 1.5 to 6.0 Volt. Microstructure and corrosion behavior of anodized magnesium used in this work as battery anode and graphite as a cathode in 3.5% NaCl electrolyte solution were studied. Anodized magnesium in 0.3 M oxalic acid has the most uniform pores of microstructures than those anodized at other concentrations. Anodized magnesium at electric potential from 1.5 Volts tend to has higher value of potential (Ecorr = -1.754 to -1.772 Volt) and corrosion current (Icorr = 2.790 to 11.690μA/cm²), and lower polarization resistance (Rp = 425.170 to 1024.700 Ω) than non-anodized magnesium (Ecorr = -1.649 Volt; Icorr = 10.984 μA/cm²; Rp = 895.510 Ω). Anodized magnesium at the potential from 3.0 until 6.0 Volt indicates the presence of oxidation on the surface which leads to the less good characteristic pattern of dynamic potential.