Ethylene furnace antifoulants

An improved method for reducing fouling and corrosion of ethylene cracking furnaces petroleum feedstocks, the improvement comprising treating the petroleum feed stock with at least 10 ppm of a combination of a phosphorous antifoulant compound and a filming inhibitor. The antifoulant compound is chosen from the group consisting of phosphite esters, phosphate esters, thiophosphite esters, thiophosphate esters and mixtures thereof, said esters being characterized by the formulas where X equals S or O, and R1, R2, and R3, are each independently selected from the group consisting of hydrogen, water soluble amine, alkyl, aryl, alkaryl, cycloalkyl, alkenyl, and aralkyl group provided that in at least one and not more than two of each R1, R2, and R3 are water soluble amines having partition coefficients greater than 1.0 mixed with a filming amount of at least 2-20 ppm imidazoline filming inhibitor prepared preferably from naphthenic or fatty acids and poly amines.