Heat Treatment Effect in the Corrosion Resistance of the Al-Co-Mn Alloys Immersed in 3 M KOH

Al-based alloys named M1, M2, M3, M4, and M5 doped with different atomic percentage (at%) of cobalt and manganese as cast and submitted at two heat treatments (600°C and 1100°C) were analyzed by using electrochemical techniques to evaluate their corrosion resistance immersed in 3 M KOH. With the heat treatments applied to the alloys, the sample M2 (65% Al, 20% Co, and 15% Mn) observed the highest corrosion resistance with Rp values of 3.0×102 , 6.2×102 , and 1.61×103 Ω·cm2 as cast, 600°C, and 1100°C, respectively. The latter was in agreement with the Icorr calculated from the polarization curves where the values decrease based on the heat treatment applied as follows: 1.60×103>6.16×102>3.07×102 mA/cm2 for 1100, 600, and as cast, respectively. Co concentration above 20% increases the corrosion current ( Icorr ) and decreases the polarization resistance of the remain samples. The chemical analysis done with EDS and X-ray diffraction made confirmed the presence of compounds such as CoAl, Co2Al5, Co2Al9, MnAl4, and MnAl6.