Spectroscopy & Analytical Techniques

The incubation criterion of the 62535 standard procedure of the International Electrochemical Commission (IEC) was modified to obtain the depletion profiles for different concentrations of each of 1,2,3-benzotriazol (BTA) and dibenzyl disulfide (DBDS) when both are present in a mineral oil matrix. Measurements on BTA concentrations ranging from 0 to of 70 mg L⁻¹ shows that its depletion profile after incubation for 72 h, at room temperature, and at 150°C in the presence and absence of a copper strip, is the same irrespective of the DBDS concentration. Similar measurements on DBDS at concentrations ranging from 10 to 300 mg L⁻¹ shows that identical depletion profiles are obtained as long as the BTA concentration is maintained in excess of 5 mg L⁻¹. The results show that a minimum BTA concentration of 5 mg L⁻¹ is needed to make the copper windings in contact with the mineral oil passive and in turn to suppress their sulfur corrosion by DBDS.