© 2021 Chamber of Turkish Electrical Engineers.This paper presents a comparative evaluation of the hydrophobicity performances of high-temperature vulcanizing (HTV) silicone rubber samples having different filler types and filler concentrations. Four different alumina trihydrate (ATH) filler types and three different filler ratios (10, 30, and 50 wt%) are considered. With the base HTV, a total of 13 different samples is exposed to AC corona discharges for two hours to assess the hydrophobicity performance of the samples. For each sample type, four test specimens are used to take more robust results. At specific time intervals, the contact angles of the samples are measured in three different locations. The results show that the specimen with 50 wt% of the precipitated ATH filler has the best performance in terms of hydrophobicity loss under AC corona discharges.