The invention belongs to the technical field of surface engineering coating, and relates to the electrostatic powder spraying technology of surface engineering. The method comprises five steps: abrasive blasting, spraying, sintering, secondary spraying and sintering, and post-processing. An electrostatic spraying sintering method is used for depositing poly(ether-ether-ketone) powder on a butt joint surface of a flange and in a part of a pipe, and there is a certain distance away from a welding part. The surface of the flange is provided with a reliable flat insulating coating layer with the thickness from 300 microns to 500 microns, and the insulating coating layer is low in water absorption, is good in insulating effect, enables different types of metal at two ends of the flange to be isolated, is good in extruding resistance for the flange when a ship or a metal engineering structure deforms, can provide a good isolation protection effect, and effectively avoids the gap corrosion caused by the galvanic corrosion caused by the isolation elimination of different types of metal, pipe connection spacer aging and pipe miniature deformation. The method is simple, is reliable in principle, is low in preparation cost, is good in insulating effect, is long in validity period, is environment friendly, and is wide in application range.