Hot corrosion properties of iron aluminide coatings produced via a two stages process on plain carbon steel

The isothermal high temperature corrosion behavior of an Fe3Al coating coated on plain carbon steel through tungsten inert gas (TIG) surface alloying with current of 40A was studied in the atmosphere of air. The specimens were tested at 700 and 900 °C for 4–100 h. SEM, EDS and XRD analyses were utilized to study the oxidation behavior of the iron aluminide intermetallic coating. The weight gain data determined a parabolic rate law. The results also revealed that the initial scale formed on the coating was predominately θ-Al2O3 which was substituted by α-Al2O3 after about 64 hours. The SEM observation and XRD results illustrated that at shorted times, when the θ phase was stable, spalling was more usual while with the increase in the amount of the α phase the spalling decreased significantly. The EDS results confirmed the presence of aluminum oxide at shorted times and iron oxide at longer times.