Study regarding corrosiveness and thermal stability of some insulating oils in contact with red cooper and S235J2G3 carbon steel

The corrosiveness and thermal stability of five types of insulating oils - both in contact and contactless with copper and S235J2G3 carbon steel - have been studied through gravimetric determination, XRF analysis and dynamic viscosity measurements. The experimental results showed that, after a heat treatment (700 hours) at 110± 30°C, the weight of the investigated samples by mineral oil drops (by volatilization) to be between 7 and 7.5%. For vegetable oils have not been registered remarkable changes in weight. The XRF analyzes revealed that the investigated new minerals oils have a sulfur content up to 0.03% and the used oil sample (30 years in transformer) up to 0.14%. Sulfur content in the vegetable oils has been not recorded. Corrosion of copper and carbon steel in the investigated oils increased due to increasing the sulfur content.