The cracking of the paint film can be divided into coarse cracking, fine cracking and double cracking from the surface phenomenon. These are all manifestations of the aging of the paint film, most of which are caused by the long-term oxidation. The paint film loses its elasticity and cracks will occur. This is not a pathological condition. If the paint film cracks soon after painting, the reasons are:
(1) The coating film of the primer is too thick, and the topcoat is applied before it is completely dry, or the primer is used as a primer with a long oiliness paint, and the topcoat with a short oiliness is covered, which will crack due to the lack of elasticity of the topcoat. Thick places shrink more, and the primer will even be exposed after the paint film cracks;
(2) The paint film is affected by external factors, resulting in cracking, such as: strong sunlight, high temperature, high humidity, the paint film is stretched and contracted by cold and heat, and the penetration of water absorption and volatilization is frequent;
(3) Indoor paint or short paint is used for outdoor painting, because of its poor resistance to ultraviolet radiation, it will crack soon after use;
(4) Adding too much volatile matter or accelerator when making paint will also cause cracking.
The prevention of paint film cracking should be corrected for the above reasons. If the paint film is wrinkled, it can be smoothed with water sandpaper and then repainted, or it should be completely removed and repainted.
