ESSO RESEARCH AND ENGINEERING CO LINDEN NJ PRODUCTS RESEARCH DIV
New information has been obtained on the importance of metallurgy and the mechanism of scuffing. K-Monel, a softer and less corrodible metal than steel, has shown some unusual behavior. Unlike steel, it scuffs at low loads, particularly if neither oxygen or water are present. Unlike steel, the addition of a corrosion inhibitor increases scuffing of K-Monel. Soft steel also behaves differently from hard steel. With a highly-refined fuel, scuffing is more severe in dry argon than in wet air, whereas the opposite order had been found on hard steel. These effects are not understood. Mixtures of methylnaphthalene in paraffinic fuels are effective antiwear, antiscuff fuels in all atmospheres and with all metals, including K-Monel and silver. Additives that are good antiwear agents are also good antiscuff agents but larger concentrations are required for good scuff control. Sulfur compounds are not effective antiscuff agents in air, confirming that they are not the lubricity compounds in conventionally refined fuels. Olefins that are unstable to oxidation tend to improve the antiwear, antiscuff properties. Their removal in the refining process probably is partly responsible for the decrease in lubricity.