1. This test method describes the detection of corrosive sulfur compounds (both inorganic and organic) in electrical insulating oils of petroleum origin. New and in-service mineral insulating oils may contain substances that cause corrosion under certain conditions of use. This test method is designed to detect the presence of, or the propensity to form, free (elemental) sulfur and corrosive sulfur compounds by subjecting copper to contact with oil under prescribed conditions.
  2. In most of their uses, insulating oils are continually in contact with metals that are subject to corrosion. The presence of corrosive sulfur compounds will result in deterioration of these metals. The extent of deterioration is dependent upon the quantity and type of corrosive agent and time and temperature factors. Detection of these undesirable impurities, even though not in terms of quantitative values, is a means for recognizing the hazard involved.