Surface Electrical Leakage on Insulators and Coatings in the Presence of Moisture Condensation

The electrical leakage of insulation exposed to moisture, particularly when salt deposits from a marine environment are also present, can degrade the performance of electrical and electronic equipment or render it inoperative until cleaned and dried. The effects of prolonged bulk moisture condensation on the surface electrical resistivities of some typical insulating materials and coatings have been studied. As in the case of exposure to relative humidities below saturation, the materials of low surface energy maintained higher resistivities. These were related to the water droplet contact angles, particularly the receding angles resulting from coalescence. Nonporous coatings with low surface energies maintained high resistivities even when applied to the poorer substrates, but porous coatings showed continual declines.