Long-term operation of composite insulation tubes often inevitably suffer from corona aging and mechani-cal damages

which will greatly reduce the insulation properties of insulators. Some power sector use PRTV persis-tent anti-fouling flash paint（permanent room temperature vulcanized）to repair the composite insulation with pow-dering

cracking and other aging phenomena. Some tests are taken on the electrical properties of composite insula-tors after repaired

but the arc discharges on the surface of composite insulation after repaired are rarely reported. Inthis paper

the PRTV coating is applied to the high temperature vulcanized silicone rubber（HTV）surface with simu-lated aging

and a dry flashover test is carried out using finger electrodes. The effect of surface discharge on the hy-drophobicity of PRTV coating is investigated by comparing the electrical properties of silicone rubber before and af-ter discharge. The results show that the hydrophobicity of the PRTV coating is decreased obviously after the dis-charge

which indicates that the surface discharge destroyed the chemical bond in the PRTV coating. Meanwhile

the discharge of the test samples with or without the existence of RTV coating are measured by three-electrode mea-surement system. The results show that the PRTV coating destroys the linear relationship between the volume resistivi-ty and the temperature variation curve ln ρv-1/T of the high temperature vulcanized silicone rubber substrate

and thesurface discharge makes the linear relationship between volume resistivity and temperature curve ln ρv-1/T irregular.