Diagnostic instrument for electrostatic powder coating

A novel instrument has been designed to diagnostically determine the quality of electrostatically deposited powder coatings. Unfused coatings are analysed by selectively removing test zones of powder with a pulsed air jet and measuring the transmission of an infra-red beam through the depleted zone. This is carried out under microcomputer control. Initial results have been obtained for two different types of industrial coating equipment consisting of; a conventional high voltage gun operating from 50 kV to 90 kV, and a low voltage ion-free gun operating from 10 kV to 30 kV. The instrument is primarily configured to monitor the adhesive properties of the powder layer, consisting of both interparticulate and particle/substrate forces. From initial results it is possible to readily differentiate between the two types of coating system, and to determine many of the conditions necessary for optimum powder deposition in either process. The adhesive properties of the high voltage coatings are considerably larger than the low voltage coatings. An analysis of the results is being made to determine the optimum coating conditions for any powder deposition process.