For this technology, an ionizing electrode, typically located at the paint gun atomizer tip, causes paint particles to pick up additional electrons and become negatively charged. As the coating is deposited on the workpiece, the charge dissipates through the ground and returns to the power supply, completing the circuit. The electrostatic field influences the path of the paint particles. Because the charged particles are attracted to the grounded workpiece, overspray is significantly reduced. Paint particles that pass a workpiece can be attracted to and deposited on the back of the piece. This phenomenon is known as "wrap."

The transfer efficiency is the percent of sprayed paint that is applied to the workpiece. Paint that is not applied to a workpiece is captured in the paint spray booth’s emission control system and ultimately disposed as waste. The typical transfer efficiency for an electrostatic paint spray system is 75%.

In conventional paint spray systems, paint atomization occurs via high velocity air jets forcing paint through small air holes in the paint gun face caps. Air pressures used in these systems range from 40 to 80 pounds per square inch (psi), with air volumes of 8 to 30 standard cubic feet per minute (scfm). The atomized paint particles travel at high velocities and have a greater tendency to bounce off the object being painted, as compared to electrostatic systems.

Paints used for electrostatic painting must be formulated with polarizable solvents. Personnel responsible for ordering the paint should coordinate with the supplier/manufacturer to ensure that they obtain the proper formulation.

No new wastes are generated when a conventional paint spray system is converted to an electrostatic paint spray system. Significant reductions in waste generation are achieved due to the electrostatic system’s increased transfer efficiency.

A potential drawback to electrostatic finishing, particularly for coating complicated surfaces, is the Faraday cage effect: a tendency for charged coating particles to deposit around entrances of cavities. The Faraday cage effect allows electric charges on a conductor to reside on the outer surface of the conductor. In the case of coating complicated surfaces, the electric charge resides on the entrances of cavities. High particle momentum can help overcome Faraday cage effects, since particles with greater momentum (larger particles or particles traveling at higher speeds) are influenced less by the electrostatic forces. However, high particle momentum also lowers efficiency.

Electrostatic paint equipment is available in three basic types: air atomized, airless, and rotating discs and bells. High-speed discs atomize the coating more finely than air atomization and direct more paint to the target. This technology is particularly efficient for the application of difficult to disperse, high-solids paints. However, the Faraday cage effect is generally greater with rotary atomizers than with air or airless types. Rotary atomizers, therefore, may not provide adequate coverage for complicated surfaces.

Proper design, operation, and maintenance of the equipment is required for its safe use. The spray booth must be well ventilated. Additional health concerns depend on the coating being applied. Inhalation of lead and zinc chromate based paints can irritate the respiratory system. Some lead compounds are carcinogenic. Solvent-based coatings can irritate the lungs and mucous membranes. Prolonged exposure can affect the respiration system and/or the central nervous system. Proper personnel protective equipment should be worn, if required.

Consult your local industrial health specialist, your local health and safety personnel, and the appropriate MSDS prior to implementing this technology.