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 degrees 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) x 4.5H(2)O) formed in the absence of CO2. In the presence of CO2 and NaCl three magnesium-hydroxy-carbonates, giorgiosite, hydromagnesite and Mg-5(CO3)(4)(OH)(2) x 8H(2)O formed. The influence of CO2 on the electrochemical corrosion process is discussed. (C) 2014 The Electrochemical Society. All rights reserved.