NaCl-induced atmospheric corrosion of MgAl alloy AM50 in semi-solid cast and high pressure die cast form; relation between alloy microstructure and corrosion
Paper i proceeding, 2013
The atmospheric corrosion behavior of the MgAl alloy AM50 has been investigated in the laboratory, in the presence of 0, 14 and 70µg/cm2 NaCl. The alloy was investigated both as high pressure die cast and in semi-solid cast (rheocast) form. Polished samples were exposed for 1-672h in air at constant temperature (22.00oC) and constant relative humidity (95%). The concentration of CO2 was 0 or 400ppm. Corrosion rate was determined by measuring mass gain and metal loss. The microstructure of the two materials was examined through optical microscopy and SEM/EDX analyses. Cross sections were prepared through the corroded samples using focused ion beam (FIB) milling. The corrosion products were characterized by SEM/EDX and X-ray diffraction. The rheocast material was observed to exhibit better corrosion resistance than the high pressure die cast alloy. The relation between alloy microstructure and corrosion attack for the two materials is reported and discussed.