Esthetic performance of thermochromic pigments in cataphoretic and sprayed coatings for outdoor applications

This study aims to assess the aesthetical performances of thermochromic coatings for outdoor applications. In details, this work focuses on the efficiency of thermochromic pigments inside cataphoretic and sprayed primers, evaluating the possible synergic effect of a protective transparent topcoat. The structure of thermochromic pigments is examined by optical microscope, and their color-changing behavior is evaluated by colourimetric measurements. Colourimetric analyses are also carried out to monitor the thermochromic performances of the coatings during exposure to an aggressive NaCl solution and UV-B radiations, and to assess the protective role of the top-coat. In addition to that, wet- and dry-abrasion tests are carried out to define the suitability of these coatings for outdoor applications where good resistance to mechanical damage is required. Thus, this work evidences the better aesthetical features of the cataphoretic primer, which, however, particularly suffers from chemical–physical degradation processes. Nevertheless, the application of the transparent topcoat allows to maintain the integrity of the cataphoretic primer. The double-layer coating exhibits a remarkable color-changing behavior even when subjected to degradation phenomena due to exposure to aggressive environments.