Silicone high-voltage insulators can be exposed to fog or rain during their operation. Water droplets appear on the silicone rubber surface and initiate partial discharges, which reduce its hydrophobicity. It is necessary to consider combined effect of the discharges and moisture. This work evaluates the hydrophobicity of a silicone rubber sample exposed to a corona discharge and then immersed in distilled water. The contact angle and the dynamic runoff of water were measured during the experiment. It is shown that the dynamic method is more sensitive than the static one. After immersion, experimental results demonstrated a longer time of water runoff from the sample on the periphery of the damaged region compared to the undamaged regions. However, the static methods show no difference between these two locations.