For automotive sheet metal painting, primers are divided into epoxy primers, intermediate primers and plastic primers. And there are two types of intermediate primers: 2k primer surfacer and 1k primer surfacer.
At present, there are many kinds of primers, putty and topcoats used in automobiles with different performances. It is very important to choose the right intermediate primers. It is related to a series of issues such as saving topcoat, reducing spraying costs, facilitating construction and improving the decorative properties of topcoat. In addition, the construction method and construction conditions of the intermediate primer, including film thickness, drying conditions, spraying technology, diluent selection, paint viscosity, construction equipment, construction environment, and the quality of the putty scraping operation will affect the quality of intermediate primer after coating, which in turn affects the quality of the topcoat. Therefore, we must pay attention to the role and the construction quality of the intermediate primers.
1. The role of intermediate primers
In the coating combination, the primer is coated under the topcoat, which mainly plays the role of enhancing the adhesion between the coatings, and also plays the role of strengthening the sealing of the primer and filling the fine traces. Therefore, the intermediate primer needs to have certain adhesion, solvent resistance and filling properties to ensure a perfect construction surface for the topcoat. As an intermediary layer between the topcoat layer and the primer layer, the putty layer and the old coating, the intermediate primer should also have good compatibility with the primer layer, the putty layer, the old coating and the topcoat layer.
2. Characteristics of intermediate primers
A. It has good compatibility with primer, putty, old coating and topcoat, such as providing good adhesion for primer and topcoat at the same time.
B. The hardness of the coating is moderate after drying, with good grinding performance and water resistance. After wet grinding, the surface of the coating is smooth, without wrinkling and peeling.
C. It has good filling performance, and can eliminate minor scratches, sand marks and small sand holes on the substrate after grinding.
D. It can prevent the solvent of the topcoat from penetrating into the primer layer, the putty layer and the old coating.
E. It has good isolation performance, which can prevent the primer layer, the putty layer and the bad substances of the old coating from oozing out to the top coating to contaminate the surface of the paint film and destroy the decoration of the top coating.
F. It can provide the topcoat with a coating surface with consistent adsorption, and at the same time, because of its good anti-permeability, it can improve the gloss of the topcoat, thus greatly improving the decoration of the topcoat.
G. The intermediate primer should have good construction properties, including temperature adaptability, rapid drying and convenient construction.
