AlanB said:
Well, called and spoke with Kenny Foley,tech services of Hydrotex and I know where saparks10 gets his info from.
He also stated that sulfur is a lubricant and that they use sulfur phosphorous technology in many gear lubes to improve lubricity.
Hmmmm, now I need to call PS.
There are numerous different kinds and states of sulfur. There isn't just one sulfur. The type of sulfur used in EP gear lubricants is active sulfur. The term active sulfur refers to the relative ability of a sulfur-containing compound to chemically react with a metal surface to form a metal sulfide. Inactive sulfur compounds do not form metal sulfides under test or operating conditions. The tendency of a sulfur-containing additive to react with a metal surface depends on the composition of the additive, the reaction temperature and the oxidation state of the sulfur in the compound.
The sulfur, naturally occurring as you would find in diesel fuel is completely different. Sulfur occurs in lubricants in several forms. The petroleum distillate fraction of solvent-refined base oils contains organosulfur compounds that carry through the refining process. By contrast, hydrocracked base stocks contain little or no sulfur as a result of the high severity catalytic process by which they are made. Similarly, synthetic base oils also do not typically contain sulfurous components.
Sulfurized Mineral Oils
Sulfurized mineral oil, made by dissolving elemental sulfur in oil by heating, is the most active form of sulfur because of the relatively weak S-S bond in elemental sulfur. Elemental sulfur exists in eight-member rings or long chains. Sulfurized mineral oil will readily stain copper under the conditions of the Copper Corrosion Test (ASTM D130), which uses a copper test strip, submerged in the test oil at 100°C for three hours as an indication of chemical reactivity to yellow metals.
Sulfurized Fatty Acids
Sulfurized fatty acids are made by chemically reacting sulfur with long chain fatty acids. They have a higher thermal decomposition temperature than elemental sulfur, typically around 260°C. As such, they do not readily stain the copper strip in the copper strip corrosion test.
Sulfur-Phosphorus EP Additives and Naturally Occurring Sulfides
Many sulfur-phosphorus EP additives thermally decompose at 250°C to 275°C and again will readily pass the copper strip corrosion test.
Sulfur compounds in solvent-refined base oils, which are also typically sulfides, are even more chemically stable. Both EP additives and base stocks are inactive based on the standard copper corrosion test. However, at the much higher localized temperatures generated under boundary lubrication, both sulfurized fatty acids and sulfur-phosphorus EP additives will decompose and form metal sulfides. Under these conditions, both additives are typically active.
Sulfurized mineral oil and other highly reactive forms of sulfur have the advantage of forming protective metal films at lower temperatures than other sulfur-containing additives. On the downside, they are corrosive to certain metal and metal alloys, particularly yellow metals, which contain copper as a major alloying element.
Modern EP gear oils contain thermally stable additives that promote system cleanliness and do not corrode yellow metals under moderate operating conditions. The goal in formulating top-tier EP gear oils is to develop additive chemistries that will carry high loads under boundary conditions and protect mating surfaces from wear while minimizing corrosiveness to yellow metals and keeping steel gear components clean.
Lubricity levels as they are mandated are lower then most pump/injector manufacturers would like to see. In this great country of regulations we happen to have some of the worst in the world when it comes to fuel standards. I couldn't agree more that lost lubricity needs to be replaced.
