The electrical surface resistivity of polymer base coating was investigated in arc-decomposed SF 6 gas. The thickness of more than 100 um was found necessary to prevent the adverse effect of arcdecomposed SF 6 gas, which penetrated the coated film and deteriorated the insulation properties of the base material. The effect of the cure condition of the coated film was also investigated by using differential scanning calorimeter (DSC). An endothermic peak due to uncured agent, which reduced the surface resistivity in arc-decomposed SF 6 gas, was observed.