Salt Fog Evaluation of RTV SIR Coatings With Different Fillers

The performance of three commercially available room-temperature-vulcanized (RTV) silicone rubber (SIR) coatings was evaluated by means of salt fog testing. Leakage current and contact angle measurements were used in order to monitor the coatings´ performance. The measurements indicated that the initial loss of hydrophobicity can be correlated to the surface discharges that develop on the material surface due to the droplets formed. In the case of the silica-filled coating, the considered los.s was observed earlier. Further, lower levels of surface activity and material deterioration were observed for the alumina-trihydrate (ATH)-filled coatings in comparison to the SiO₂ filled. The results can be correlated to the filler efficiency and especially to the thermal conductivity achieved. For the considered formulations, the silica-filled coating appeared to have the lowest value of heat conductivity. Finally, for the ATH-filled coatings, additional parameters, such as the particle size, must be considered.