Importance

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Abstract

A coating and method for reducing the tendency for coke and gum deposits of hydrocarbon fluids to form and adhere to a surface at an elevated temperature. The coating enhances surface flow conditions along the surface so as to reduce both surface reaction time and concentration of deposit precursors (radicals and atoms) that provide for polymer growth. The coating has a smooth surface that is free of microscopic pits and scratches, and preferably has a surface roughness not greater than about 16 microinches (about 4 micrometers) R.sub.a. The coating is also preferably resistant to chemical attack from contaminants in the fluid, and inhibits diffusion between the fluid and surface. In addition, the coating has a low surface wettability to hydrocarbons, meaning that the tendency for hydrogen in the fuel to bond with atoms at the coating surface (chemisorption) is reduced or eliminated. In one embodiment, a smooth and preferably amorphous coating of metal oxides is deposited by a chemical vapor deposition (CVD) process on a smooth and essentially oxide-free surface, followed by a layer of metal atoms or metal-metal compounds that exhibit low affinity for chemisorption. In a second embodiment, chemisorption is avoided by forming the coating such that potentially electronegative atoms in the coating are tied-up with other strong chemical bonds.

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First Claim