Abstract: A method for protecting low-carbon steel and stainless steel from coking and corrosion at elevated temperatures in corrosive environments, such as during ethylene production by pyrolysis of hydrocarbons or the reduction of oxide ores, by coating the stainless steel with a coating of MCrAlXSiT in which M is nickel, cobalt, iron or a mixture thereof, X is yttrium, hafnium, zirconium, lanthanum, scandium or combination thereof, and T is tantalum, titanium, platinum, palladium, rhenium, molybdenum, tungsten, niobium, boron or combination thereof. A blended powder composition to produce a desired MCrAlXSiT surface alloy may be applied to the substrate. The overlay coating and stainless steel substrate preferably are heat-treated at about 1000 to 1200° C. for about 10 minutes or longer effective to metallurgically bond the overlay coating to the substrate and to form a multiphased microstructure.