Based on the overhead lines and outdoor switchgear operation and maintenance, it is known that contamination and subsequent moisturizing of the insulators surface lead to the surface discharge development and consequently discharge voltage of the insulators is reduced. It is necessary to ensure uniform distribution of the voltage applied in the axial direction of the insulation when designing suspension insulator string. The article examines the moisturizing influence and coatings applied on the area of the greatest electric field non-uniformity on the voltage distribution along a contaminated suspension string of glass insulators. Four coatings are considered: silicon sealant, insulating varnish, insulating enamel and epoxy conductive glue. The test phase voltage, assumed to be 115/V3kV in the present research, is varied in steps of 2.5% from 80% to 120%. The number of insulators in the suspension string is varied from 13 to 9. The dependencies of voltage distribution non-uniformity factor on applied test voltage are obtained. Conclusions about the proposed coatings performance for the contaminated suspension insulator string under study are drawn. © 2023 IEEE.