Iron aluminide is one of the most attractive candidates for high-temperature corrosion-resistant coating materials, since it exhibits superior high-temperature resistance to oxidation and sulfidation, good wear resistance, and low cost. For many industrial structure applications, including coal-fired power generators, thick high quality coatings offer resistance to severe environments of high-temperature corrosion and erosion as well as the required very long service life. However, although iron aluminide coatings have been extensively explored with various coating processes including CVD processes and thermal spray processes, it is still difficult to produce thick iron aluminide coatings with full density and satisfactory bonding to the substrate. In this study, the plasma transferred arc (PTA) process was used to produce iron aluminide coatings on steel substrates, demonstrating that there are unique advantages using the PTA process in comparison with other thermal spray processes. The first advantage of PTA process is that the substrate is part of the power circuit so that the temperature of a thin substrate surface layer can reach the substrate material’s melting point, which enables a metallurgical bonding between the coating and the substrate. Another important advantage of the PTA process is that the coating layer is usually completely melted during the process so that porosities and oxide inclusions can be kept to minimum. Experimental results in this study demonstrate that the coatings by the PTA process were phase-pure porosity-free iron aluminide metallurgically bonded to the steel substrates, and the coating also exhibits superior corrosion resistance at high temperature.