Information on the method for assessing the crack resistance of paint and varnish coatings is given. A method is proposed, based on the ratio between the length of the crack, the Vickers indenter imprint, and the fracture toughness. Numerical values and stress intensity factor in coatings are given, depending on the type and duration of aging, porosity of the cement substrate, and the quality of the appearance of the coatings. It is established that with an increase in the roughness of the coating surface, the value of the stress intensity coefficient is increased. The increase in the moisture content of the substrate at the time of application of the paint composition leads to the appearance of a more defective structure of the contact layer “coating-substrate” and a greater propensity to cracking. It is revealed that there is a value of the optimum substrate moisture, for each particular coating in terms of its fracture toughness. It is shown that during the aging of protective and decorative coatings of the exterior walls of buildings, a mechanism of their destruction from elastic ductile to brittle changes occurs.
Part of the book: Coatings and Thin-Film Technologies