A review is given of the differences between corona and triboelectric gun design. Different charging systems are described for the corona gun including multiple corona needles and the effect of their location at the gun extremity. Measurement of charging efficiency is made among these types of guns. The basic design features of the triboelectric powder gun are reviewed and a measurement system is described to obtain a quantitative efficiency of the coating equipment. Novel triboelectric guns are described to enable the use of a wider range of powders. A comparison is made between the relative merits of the two systems and the utilisation of the optimum system is explained for a wide variety of different applications and workpiece geometries. The technology and the plant solutions in correlation with the types of gun are constantly being developed in order to improve the total installation, e.g. the plastic booth, to open up further fields of applications (workpieces of glass, ceramics, plastics) and to find out novel and more effective working principles. In the years to come systems engineering in big plants will be making distinct progress from partial to full-scale automation of the coating lines. For these automatically controlled powder applications the tribo guns, with their charging current are of great importance, which indicates the faultless operation of the gun and can be used as control parameters, e.g. the powder output.
