Comparison of corrosion behavior of Al‐Mn and Al‐Mg alloys in chloride aqueous solution

The microstructure and corrosion behavior of Al‐Mn alloy 3A21 and Al‐Mg alloy 5A05 in 3.5% NaCl solution were examined and compared. The results of the microstructure survey performed by optical microscope confirm the inhomogeneous nature of the intermetallic particles of the two alloys. The X‐ray diffraction (XRD) analysis reveals the presence of intermetallic Al 6 Mn and Al 6 (FeMn) particles in the 3A21 alloy and Al 3 Mg 2, Mg 2 Si and FeAl 3 particles in the 5A05 alloy, respectively. Electrochemical results, in parallel with corrosion morphology characterization, show that these two alloys both suffer pitting corrosion type attack under the conditions employed in the present study, with better corrosion resistance and stronger repassivating capability for the 5A05 alloy. Furthermore, the validity of the difference ΔE (E pit –E corr , E corr –E prot ) and E ptp as criteria for susceptibility to localized corrosion of aluminum alloys are also discussed.