An additive to a flame reaction forms noncorrosive deposits on cooler metal surfaces, which deposits are more stable than Na2SO4 or K2SO4. By adding molybdenum salts to the flame, an alkali polymolybdate is produced on the cooler metal surface and corrosion is inhibited. Deposition appears to closely reflect the relative thermodynamic stabilities of these salts. The flame processes all chemical molybdenum salt precursors as equivalent sources of molybdenum. The level of molybdenum required is equal to 2 times or more that of the alkali on an atomic basis in the flame environment. The nature of the fuel purity and possible alkali reduction schemes invoked will control the actual quantity and mixing method of the additive. The additive may be directly mixed into the fuel or injected into the burned gas regions of the combustor.