The effect of annealing temperature on the corrosion behavior of copper in insulating oil contained corrosion sulfur

Copper corrosion in transformers is one of the serious problems affecting the life of the transformers. Much work has been done to improve corrosion resistant of copper. Grain boundary engineering (GBE) is an effective method to enhance the property of corrosion resistant by optimization of deformation and heat treatment processes to change the number and distribution of the special grain boundary, thus improving material certain macro performance associated with grain boundaries. In this study, pure copper first cold rolled 35%, then annealed at varied temperature. Then, the evolution of grain sizes and special grain boundaries after the processing and annealing have been particularly analyzed by electron back-scatter diffraction (EBSD). Meanwhile, according to IEC62535 standard, the copper samples with two layers insulating paper were immersed in corrosive oil for 72 hours at 150°C. The corrosion of copper samples was investigated. It shows that annealing temperature affects seriously the number of special grain boundary and the grain size of copper sequentially enhancing the corrosion resistant of copper in insulating oil contained corrosion sulfur.