The differences in potential corrosive effects of sulfides and disulfides in insulating oils

This paper describes work performed in an attempt to bring more clarity regarding the differences in potential corrosive effect between sulfides and disulfides at specified reaction conditions as defined in ASTM 1275 B. SEM/EDS was used to further evaluate testing results. The results show that Dibenzyl disulfide (DBDS) has a strong tendency to form copper sulfides while Dibenzyl sulfide (DBS) display no tendency at all to form copper sulfides in the virgin insulating oils, but the reactivity of DBS increase if in the thermally degraded oils. In addition, the insulating paper decrease the oxidation of the copper surface due to that oxygen is adsorbed and consumed when migrating through the cellulose phase. With the improvement of surface smoothness, the specific surface area accessible for reactions will decrease and consequently it is more difficult for the copper to be corroded by DBDS.