A New Testing Concept for More Precise Selection and Durability Optimization of Topcoats

The durability of coatings is often evaluated by the impact of standardized weathering cycles. While such tests may yield well-differentiated damage patterns, they do not reveal which specific weathering parameters—particularly temperature, moisture, or radiation exposure—contributed to the formation of each observed damage type or to what extent. Consequently, it remains unclear (i) how exactly each individual formulation should be modified in order to optimize coating durability, and (ii) which of the tested coatings are particularly (or less) suitable for specific climatic conditions. In the present study, a testing concept is introduced that is primarily based on conducting single-parameter variants of the fluorescent weathering cycle according to DIN EN ISO 16474-3:A (P1). These variants were designed in such a way that, by comparing the weathering results obtained from sets of three color-identical topcoat systems, conclusions could be drawn regarding the aforementioned aspects (i) and (ii). Indeed, it was demonstrated that formulation modifications derived from the observed results led to a markedly improved weathering stability of the topcoat systems, particularly with respect to their previously identified weaknesses.