There are many acrylic-based coatings (like the humiseal recommendation) which apply a very light coat and have minimal or no electrical effects.
Please note however, that acrylic coats should be used where the degree of required environmental protection is low, i.e. normal condensation.
For more aggressive environments, i.e. coastal areas with high humidity and salinity, and certainly automotive environments, a better silicone or urethane-based coating is required.