RP 621 Dielectric strength of a coating refers to the ability of an insulating coating material to withstand electrical stress without breaking down or allowing current to pass through it. It is measured as the maximum voltage the coating can withstand per unit thickness before electrical failure occurs, typically expressed in kV/mm or V/mil. A coating with high dielectric strength provides excellent electrical insulation, prevents leakage currents, and protects underlying components from electrical damage, corrosion, and environmental exposure. This property is especially important in applications such as electrical equipment, transformers, motors, printed circuit boards, and protective industrial coatings where reliable insulation performance is required.