Dibenzyl Disulfide (DBDS) is one of several sulfur compounds known to cause copper corrosion in
transformers under certain circumstances. Remedial processes such as adsorbents, absorbents, and oil
change-out have been known to reduce the concentration of DBDS in the oil. However, if not destroyed
or removed below several mg/kg (ppm), breakdown of the DBDS to benzyl mercaptan or a DBDSCopper
complex can still cause corrosion of copper and the formation of copper sulfide. Passivators are
also being used to protect the copper against corrosive sulfur attack but does not remove or destroy any
corrosive sulfur species or those sulfur compounds that can become corrosive. This paper discusses a
process in which the destruction of DBDS is complete to below 1 mg/kg, can be performed at the
transformer, and the oil reused in the same unit.