Inhibition effectiveness and depletion characteristic of Irgamet 39 in transformer oil

Recently, a large amount of power transformer dielectric failures caused by the copper sulfide (Cu2S) contaminant are reported, which is a semi-conductive black solid material produced by the reaction of DBDS additive and copper under certain temperatures. Irgamet 39 is used as metal passivator in transformer oil that can delay the corrosion process in laboratory investigations, which forms a protective layer on the copper surface to prevent the harmful reactions between the corrosive sulfur and copper. However, the inhibition effectiveness of Irgamet 39 on mildly corroded copper surface and its depletion characteristic are still not clear. Herein, corroded copper was treated with Irgamet 39 under different aging conditions, suggesting Irgamet 39 could dramatically improve the properties of copper strips as determined by EDX analysis. Evaluation of the stability of impermeable layer under continuous ageing processes suggests that maintenance of specific concentration of metal passivator is critical for the stability of protective layer. In addition, the depletion characteristic of Irgamet 39 was investigated under different ageing conditions with variables like temperature, copper, insulating paper and atmosphere factor. It indicates that oxygen plays an important role in consumption of the metal passivator.