Thermal curing coatings have made up most of the coatings in coil coating processes for the past 100 years. Lately, environmental regulations have deemed these processes unsustainable due to required amount of energy and use of polymers derived primarily from fossil constituents. Within this decade, radiation curing has emerged to provide the industry a greener alternative to thermal curing. In addition to energy savings, reduced VOC emissions, more compact and simple line setups, and improved working place safety strongly promote transition to radiation curing technologies. This paper presents the key drivers for the upcoming paradigm shift, and then discusses some of the recent evaluations related to compatibility of current pretreatment formulations with UV-curable coatings. Furthermore, examples of coating stability assessments are presented. The coating applications were performed in the laboratory, and exposures were carried out both in accelerated exposure and outdoor exposure. The results show that the same pretreatments do not necessarily work for both thermal curing and UV curing coatings, and the root causes are discussed from the perspective of molecular-level changes at the interfaces. Surface sensitive tools, such as XPS, were utilized, and modern cross-sectioning and SEM/EDS mapping was applied for assessment of the exposed panels.
