Thermosetting powder coatings: Finish appearance and durability at cure window corner points

Abstract

Abstract This project investigated the finish quality of automotive powder coatings in terms of appearance, adhesion and chip resistance. Two powder basecoats (red and black), of three particle sizes, and a colorkey primer (red) were studied in relation to the process temperature and time pairs based on the cure window provided by the paint manufacturer. The appearance was quantified using the contrast values of the wave-scan structure spectrum elements (Wa, Wb, Wc, Wd, and We). Gravel and scratch tests were used to quantify adhesion and chip resistance properties. It was found that long-waves (Wc, Wd and We) were less affected by the curing time and temperature variation. The contrast values of short-waves (Wa and Wb) increased with increasing process temperature and time. The most dramatic increase was observed at high process time and temperature. High process temperatures (193 °C) resulted in good long-wave coverage. Small contrast values of the long-waves were obtained for all cure conditions, for both red and black basecoats. The results for short-waves were not as consistent. This work suggests that powder basecoats and colorkey primers can yield appearance qualities comparable to water-borne counterparts.