The ppgi coating is an empty tissue. Water and corrosive substances (sulfate, etc.) in the air invade according to the poor part of the coating, corrode under the film, and the coating bubbles out. In addition, even with the same coating thickness, the secondary coating is denser than the primary coating. According to foreign reports and the results of relevant corrosion tests, positive coatings can effectively prevent the intrusion of corrosive media. Due to the different anti-corrosion mechanisms of primers and topcoats, not only the main film thickness is required but also the primer (5m) and surface The thickness of the paint (15m) is different. Only in this way can the corrosion resistance of each part of the coated board be balanced.
PPGI requires thicker coatings because they provide a longer service life guarantee. The requirement for post-coating depends on the use of the core board, which only requires a layer of adhesive primer, and because the indoor corrosive environment is at least 10 meters thick, the shaped steel plate also requires two layers of coating.
The selection of PPGI color is mainly considered to be consistent with the surrounding environment and the user's preferences, but from a technical point of view, the selection of light-colored paint pigments is large, and inorganic pigments with good durability (such as titanium dioxide) can be selected. The heat reflection ability of the paint (the reflection coefficient of the double black paint) is lower in the summer paint itself, which is beneficial to the life of the paint. In addition, even if the color or powder of the coating is changed from the original color, the light color film has little effect on the appearance. There are many organic colors of deep colors (especially bright colors), which are easily faded when exposed to ultraviolet rays, and the color will change in just 3 months.
For PPGI, the thermal expansion rates of the coating and steel plate are different, especially the linear expansion coefficients of the metal substrate and the organic coating.
