Materials evaluation of the aging of protective and decorative coatings

Information on the application of thermodynamic parameters to assessing the aging of coatings is presented. It is proposed to divide the aging process into a number of quasi-stationary processes, for which the equations of reversible thermodynamics can be applied. It was found that with aging of the coatings, an increase in the specific heat of wetting and a change in entropy are observed. Revealed different rates of change in the free energy of the coatings in the process of moistening. The maximum decrease in free energy, which characterizes the course of structure-forming processes, occurs at the early stage of moistening. Further moistening leads to the predominance of destructive processes characterized by a decrease in the value of changes in free energy. With UV irradiation at the first stage of aging, the change in the specific free energy is caused by structure formation with an increase in volume. Subsequently, a decrease in the rate of change of free energy indicates a slowdown in the process of structure formation and competition between the process of structure formation and destruction with a decrease in the volume and weight of the coating. With further UV irradiation, the change in free energy increases, but this time due to the destruction occurring in the system.