1. Outcropping
Reasons and measures:
(1) The coating has poor hiding power;
(2) Before use, the settled pigment is not stirred up, or the stirring is not sufficient, resulting in a decrease in hiding power;
(3) The paint is too thin and sprayed too thin;
(4) The thickness of the sprayed film is uneven;
(5) The color contrast of the base paint is too large. For the metallic flash paint, since the base paint is sprayed very thinly, the color of the intermediate coat should be similar to that of the top coat.
Two, bite the bottom
Bottom biting is the phenomenon that when the upper layer of the coating is sprayed, the solvent in the paint will cause serious swelling and wrinkling of the bottom layer and the phenomenon of falling off. The reasons and measures are as follows.
(1) Apply the next layer before the bottom layer is completely dry. For different paint varieties, paint strictly according to the construction interval.
(2) The primer and the topcoat are not compatible, and the primer film is easily swelled by the strong solvent in the topcoat. Such as alkyd primer / nitro finish (or thermoplastic acrylic enamel), the most prone to bottoming phenomenon. Because the oxidative crosslinking process of alkyd paint film is slow and the paint film is soft, the strong solvent in the enamel paint easily penetrates into the bottom layer to make it swell and wrinkle. During construction, you can choose a quick-drying nitro (or acrylic) paint with a high pigment-to-base ratio for thin coating and sealing.
For two-component coatings, occasional bottoming also occurs. For example, when the A/B two components are reconciled, the curing agent component is added less, so that the crosslinking density of the bottom layer is not enough, the coating film becomes soft, and it is easy to be swollen and bitten by the top coating.
(3) The surface coating is too thick once sprayed, and the strong solvent that stays for a long time has the opportunity to penetrate into the bottom layer in large quantities and swell and wrinkle. During construction, you can spray a thin layer first, and then spray again after the surface is dry.
