Review Article Proc IMechE Part D: J Automobile Engineering 1–20 Ó IMechE 2017 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0954407017695159 journals.sagepub.com/home/pid Effects of automotive paint spray technology on the paint transfer efficiency – a review Sadegh Poozesh, Nelson Akafuah and Kozo Saito Abstract Automotive spray painting is among the most sophisticated and controlled industrial painting operations currently per- formed. Nevertheless, improvements in it are still sought in efforts to minimize the costs, the energy use and the envi- ronmental impacts. One compelling aspect of improvement is the paint transfer efficiency, i.e. the amount of paint that remains on a vehicle relative to the amount supplied to the paint applicator during coating operations, because currently it has been estimated that the overall paint transfer efficiency in the automotive industry is between 50% and 60%. Hence, this review assesses current automotive spray coating technologies with respect to their transfer efficiencies and discusses the fundamental and operational parameters that influence it. A comprehensive characterization of paint spray applicators (air sprayers, high-volume low-pressure sprayers, airless sprayers, air-assisted airless sprayers, rotary bell ato- mizers, electrostatic sprayers, and effervescent atomizers) is included. Some problems associated with evaluating and improving their paint transfer efficiencies are discussed. Also, the potential of and the technology needs for developing these applicators are considered. Keywords Paint transfer efficiency, paint spray applicator, surface finish quality, droplet size, spray coating technology Date received: 26 July 2016; accepted: 24 January 2017 Introduction The demands on and the performance requirements for automobile coatings are significant. Automobile buy- ers’ expectations of durable, flawless, and radiant sur- face finishes depend not only on the visible surface but also on the necessary integrity and quality of the under- lying metal or synthetic body panels. Hence, even before applying the final surface coatings, it is now common practice to apply anti-corrosion and stone- chip resistance. 1 When these subsurface coatings are coupled with surface finishing, they encompass a com- plex set of steps that are implemented in which materi- als and application processes have to be robust, flexible, and economical for mass production processing. 2 Operationally, automotive painting processes include sequenced applications of distinct layers, with each hav- ing functional relationships which influence the previ- ously applied layer and the subsequently applied layer (Figure 1). These functional relationships impart the desired adhesion, protection, and appearance properties for which modern vehicles are known. 2 Figure 1 details successive stages that a body in white (the resulting structure from welded automobile body sheet metal components) goes through in a typical paint shop. It is should be noted that the dashed boxes in this figure show a wet-on-wet-on-wet (3-wet) coating process which uses a 3-wet approach that applies the primer coat, the basecoat, and the clearcoat before curing; it decreases the energy consumption and increases the production rate. The recently published review of the automotive coating process by the same research group 3 has given more details. Spray coating The anti-chip and primer-surfacer coatings, and also the basecoat and the clearcoat, are applied by spraying. Department of Mechanical Engineering, University of Kentucky, Lexington, Kentucky, USA Corresponding author: Sadegh Poozesh, Department of Mechanical Engineering, University of Kentucky, 151 Ralph G Anderson Building, Lexington, KY 40506, USA. Email: sadegh.poozesh@gmail.com