Effects of coating thickness of RTV silicone rubber on its electrical performance

The effects of coating thickness of room temperature vulcanizing (RTV) silicone rubber on its electrical performance in wet and contaminated conditions were investigated. The dependence of the leakage current and the number of current pulses on the thickness of the coating were determined as a function of time of exposure to combined electrical stress and salt-fog. The time to failure of the coating as a function of its thickness was measured. A lower leakage current developed on a thinner coating while a thicker coating yielded a longer lifetime. Determination of the surface roughness and contact angle were made to correlate the physical surface condition with the leakage current as a function of coating thickness. The mechanisms responsible for the observed phenomena are suggested and discussed