Abstract: In order to study the corrosive properties of transformer oil after dibenzyl disulfide(DBDS) antioxidants are added and the corrosion inhibiting abilities of metal deactivators, a series of thermal aging tests are carried out on Oil Samples A and B in the laboratory. First, the thermal aging test is conducted to test the corrosive sulfur compounds by ASTM D1275B method. Then the thermal aging tests are carried out on Oil Sample A after adding a certain amount of metal deactivator (Irgament 39) at 130 ℃ to analyze the change of the dissolved gas contents in the oil. The study concludes that DBDS is one of corrosive sulfur compounds, while the metal deactivation is not. Metal deactivation can effectively prevent the occurrence of sulfur corrosion. However, it also consumes itself rapidly with the thermal aging. The contents of dissolved gases in the oil, such as H₂, CO and CO₂, increase significantly as a result of adding metal deactivator in the oil. which needs more attention regarding their impacts on oil chromatographic results, It becomes particularly critical in the diagnosis of transformer faults to avoid misjudgment.

Key words: transformer oil, corrosive sulfur, metal deactivator, dissolved gas in oil, chromatography analysis