Cleaning metal surfaces with hydrocarbon solvents

Claim 1

IN A PROCESS FOR CLEANING METAL SURFACES OF EQUIPMENT SUCH AS TANK CARS, STORAGE VESSELS, TRANSFER LINES, AND THE LIKE WHICH HAVE BEEN CONTAMINATED BY TARRY OR RESINOUS PRODUCTS SUCH AS CRUDE OIL, FUEL OIL, ASPHALT AND OTHER PERTOLEUM RESIDUAL PRODUCTS, THE STEP OF WASHING THE METAL SURFACE AT ELEVATED TEMPERATURE WITH A DISTILLATE NON-VISCOUS HYDROCARBON FRACTION WHICH CONTAINS AN ADDITIVE COMBINATION ESSENTIALLY CONSISTING OF ABOUT 0.2 TO 2.0 WEIGHT PERCENT OF A DETERGENT-DISPERSANT CONSISTING OF A NON-GASEOUS HYDROCARBON WHICH HAS BEEN REACTED WITH A PHOSPHOROUS SULFIDE AND THEREAFTER HAS BEEN NEUTRALIZED WITH A BASIC REAGENT SELECTED FROM THE CLASS CONSISTING OF BASIC COMPOUNDS OF ALKALI AND ALKALINE EARTH METALS AND ABOUT 0.4 TO 1.0 WEIGHT PERCENT OF AN N-ALKYL PROPYLENE DIAMINE HAVING THE FORMULA RNHCH2CH2CH2NH2 WHEREIN THE ALKYL RADICAL R IS SELECTED FROM THE GROUP CONSISTING OF N-CETYL AND FATTY ACID RESIDUE DERIVED FROM LAURIC ACID, COCONUT FATTY ACIDS, SOYA FATTY ACIDS AND TALLOW FATTY ACIDS.