A new process for intermetallic coating on metals based on the arc surface melting has been proposed, and its feasibility has been experimentally investigated performing an NbAl3 coating on a niobium plate. A thin aluminum plate was placed on the top surface of a thick niobium plate, and a tungsten arc heat source was supplied onto the aluminum plate. The aluminum plate and the top surface of the niobium plate were melted at the same time. The two liquids were mixed and solidified on the niobium plate resulting in the formation of coating layer of intermetallic niobium aluminides. The concentration of aluminum of the coating layer decreased as the position from the surface increased, resulting in a graded change in constituting phases from NbAl3, to NbAl3 and Nb2Al eutectic dual phases, to Nb3Al, and finally to the base metal of niobium. When the optimum arc processing conditions were chosen, a thick NbAl3 layer occupied most of the coating layer.