A comparative study on the corrosion behavior of AZ80 and EW75 Mg alloys in industrial atmospheric environment

Mg alloys exposed in different environments, atmospheric pollutants and meteorological factors as well as the microstructure of Mg substrate have an important influence on their corrosion resistance. In this paper, the corrosion behavior of Mg-Al series of AZ80 Mg alloy and Mg-RE series of EW75 Mg alloy exposed to Shenyang industrial atmosphere for one year was studied. The surface and cross-section corrosion morphologies were observed by the Scanning electron microscopy (SEM), and the chemical composition of corrosion products was analyzed by Raman spectroscopy and Energy Dispersive Spectrometer (EDS). The corrosion rate and corrosion mechanism of both Mg alloys were compared. The results show that the atmospheric corrosion behavior of AZ80 and EW75 Mg alloys is dominated under the interaction of pollutants (S, Cl and dust), meteorological factors (relative humidity, temperature, and rainfall) together with the microstructure of Mg substrate (second phases, alloying elemental distribution). The corrosion of AZ80 Mg alloy starts from the central area of α-Mg matrix where shows a low Al solid solution, and then propagates along the depth direction of β phases to form pitting corrosion. For EW75 Mg alloy, the dendritic phases and α-Mg matrix are both corroded to exhibit uniform corrosion status due to the weak micro-galvanic corrosion effect.