AC failure evaluation method of silicone rubber based on the proportion of hydrophobicity loss area in corrosive environment

•Electrical aging test of silicone rubber in a corrosive environment is firstly carried out.•Illustrate the flashover gradient of silicone rubber has a negative power function relationship with the charging duration.•Proposes the area ratio k of the hydrophobic loss area on the surface of silicone rubber to evaluate its insulating state.•Illustrate k = 0.35 can be used as the critical condition to characterize the failure of silicone rubber composite insulation.