The Roll of Acidity and Basicity of a Grease in Relation to Its Effectiveness as a Lubricant and Corrosion Inhibitor

摘要

A series of twenty four greases were selected for this work. Eight of the greases were commercial greases selected from a variety in use today. Eight other greases were made up from an uninhibited calcium hydroxy stearate grease with various combinations of extreme pressure agents, anti-oxidants and rust inhibitors as additives. Eight greases were also prepared from uninhibited MIL-G-10924B grease and the same combination of additives used in the preparation of the calcium hydroxy stearate greases. Acid numbers were determined by the Rock Island Arsenal Method, Fed. Std. 791a-5105.3, ASTM D-974, ASTM D-974 modified, and ASTM D-664. There was a wide variation in the acid and base number obtained by these methods, indicating that each method measures a different property of the grease. Wear and oxidation tests made on the greases were the Shell Four Ball Wear, Falex Rate Wear, Copper Corrosion, Oxidation Stability, and Rust Preventive Properties of Lubricating Greases. It was found that a high acid number does not always indicate poor wear or poor oxidation stability. Both molybdenum dibutyldithiocarbamate and the additive containing molybdenum, sulfur, and phosphorus, when added to the two uninhibited greases gave an increase in acid number and a decrease in wear scar. (Author)