The effect of hot-dipped aluminum coatings on Fe-8Al-30Mn-0.8C alloy

The morphology and microstructure of an intermetallic layer formed on the surface of Fe-8Al-30Mn-0.8C alloy by hot-dip aluminization treatment have been examined in detail. The phases present in the coating are unambiguously identified by means of transmission electron microscopy. After aluminization, a two layer coating was formed consisting of an external Al layer and a (Fe, Mn)₂Al₅ intermetallic on top of the substrate. The (Fe,Mn)₂Al₅ compound has an orthorhombic structure with lattice parameters a = 0.752 nm, b = 0.667 nm and c = 0.417 nm. The activation energy (E_FeMnAl) for the growth of such an intermetallic layer is calculated to be 52.7 kJ/mol. These results are different from those observed in aluminized low-carbon steel (E_Fe). The difference between E_FeMnAl and E_Fe is attributed to the alloying elements (Mn) in the present alloy. Environmental salt fog corrosion and high temperature oxidation tests were carried out to examine the corrosion and oxidation resistance. The results indicated that both the corrosion and oxidation resistance of the Fe-8Al-30Mn-0.8C alloy treated by hot-dip aluminization can be significantly increased.