An electrostatic spray gun (10) having an air powered alternator-turbine (14) with a rotating impeller (24) therein mounted in bearings (18) is provided with bearings (18) which are coated with a solvent resistant material. This coating is provided on all surfaces of the bearing (18) except for the inner diameter (18A) which contains the impeller (24). This construction prevents leaching of the oil out of the bearing (18) and into the airstream and also is resistant to paint should the spray gun (10) become immersed in such.