Apparatus for high pressure impact coating

A process and apparatus for high pressure impact coating of portions of workpieces such as the threaded openings in fasteners in avoidance of contaminating undesired portions of the workpieces with the coating material. A metered quantity of coating material is charged into a passageway and moved by low pressure air to a chamber ahead of an atomizing nozzle. High pressure air is introduced to the passageway and the coating material is fogged into a chamber defined by the workpiece and cooling. Proliferation and impingement of the cloud on the selected surfaces follows under vented conditions. A constriction in the vent line achieves the necessary delay and sets the system for accomplishing the coating. The machine structure facilitates use of the coating device with a wide range of female threaded fasteners and achieves the process steps while providing for flushing the lines and drying the working structure.