ARTIFICIAL TESTING AND EVALUATION OF RTV COATINGS IN A SALT-FOG CHAMBER

The electrical performance of room temperature vulcanizing (RTV) silicone rubber insulator coatings under accelerated aging in a salt-fog chamber for artificial testing is reported. The RTV coatings were evaluated in fog produced from saline water at 900-mu-S/cm conductivity. The effect of the contaminants deposited during dry band arcing is evaluated with respect to the performance of RTV coatings. The increase of the leakage current and the corresponding decrease of the contact angle on the surface of the coating are shown to be related to the contaminants on the RTV-coated surfaces. Five cleaning methods to remove the contaminants from the coated surface are examined, using leakage current and contact angle measurements as indicators of their comparative effectiveness. Energy dispersive X-ray analysis was used to determine the composition of the scale on the RTV coating surface and in the bulk of the coating.