NaCl-Induced Atmospheric Corrosion of the MgAl Alloy AM50-The Influence of CO2

Journal article, 2014

The NaCl-induced atmospheric corrosion of the MgAl alloy AM50 has been investigated using 99.97% Mg as reference. Polished samples were exposed up to 672 h in 95.0% RH air with 400 ppm or 0 ppm CO2 at 22.00°C. Samples were analyzed gravimetrically and by SEM/EDX, XRD and XPS. CO2 inhibited atmospheric corrosion with alloy AM50 corroding 6–7 times faster in the absence of CO2. Brucite and meixnerite (Mg6Al2(OH)18 × 4.5H2O) formed in the absence of CO2. In the presence of CO2 and NaCl three magnesium-hydroxy-carbonates, giorgiosite, hydromagnesite and Mg5(CO3)4(OH)2 × 8H2O formed. The influence of CO2 on the electrochemical corrosion process is discussed.