As the topcoat is different, the secondary paste used in conjunction with it should also be different. Reasonable selection of surfacer paint is the key to avoiding quality problems in painting.
When the old paint film is baking varnish paint or acrylic polyurethane paint, it is not a big problem to choose nitro-type surfacer, but pay attention to its quality, and the interlayer adhesion and water resistance must meet the requirements.
When the old coating film is modified acrylic or synthetic cellulose acrylic lacquer, it is advisable to use polyurethane surfacer. This kind of secondary slurry has good coating performance and good covering effect. Even if there are some problems with the old coating film, there will be no quality problems. But it should be noted that this kind of secondary slurry is not suitable for local repairs. When repairing the edge junction between putty and old coating film, it is easy to wrinkle, so this secondary slurry is only suitable for old coating film or putty. of the entire coverage.
The coating performance of thick-coated synthetic resin surfacer is not as good as that of polyurethane surfacer, but it is often used because the solvent used in it has weak solubility, will not corrode the primer, and has a faster drying speed. For this kind of secondary paste, the focus should be to check its interlayer adhesion and foam resistance.
For nitro-based and acrylic surfacers, if the foaming resistance and interlayer adhesion are good, the covering effect will be poor; otherwise, if the covering effect is good, the first two performances will be poor. Therefore, it is necessary to check its solvent evaporation performance, covering effect, water resistance, fullness, construction performance, etc.
In places where the putty coating area is wide such as full coating, and when the old coating film is wrinkled, it is better to use polyurethane surfacer. In addition, thick-coated synthetic resin surfacer is also convenient in terms of workability. The usage of these secondary pastes sometimes varies with different manufacturers, so care should be taken not to make mistakes. If it is necessary to dilute the surfacer coating, the designated special thinner should be used, otherwise the performance will be affected.
Some polyurethane secondary pastes are called non-polishing secondary pastes, but in fact, as the secondary paste layer continues to harden, the interlayer adhesion tends to decrease. In order to improve the interlayer adhesion, light sanding is still required. Leaves sanding marks on the surface to improve adhesion to the topcoat.
