The quality control before steel strip coating is mainly the control of the whole surface treatment process, that is, the control of degreasing section and chemical section. The quality of surface treatment (degreasing and chemical formation) determines
the quality of coating, and directly affects the physical indexes such as flexibility and impact resistance of coating, as well as the products of color coated sheet. Coating adhesion. Therefore, the quality control before coating is the first step
to ensure the whole coating process, and is also the basis to ensure the quality of color coated sheet products.
(1) Degreasing section. The degreasing section mainly controls alkalinity, temperature, spray pressure, nozzle injection, friction effect of scrubbing roll and conductivity of deionized water.
(2) Segmentation. The formation section mainly controls the roll pressure of the chemical roller coating machine, the concentration of the chemical solution, the wet film thickness of the chemical coating, the appearance color of the film, the drying temperature of the drying furnace and the hot air circulation, etc.
Checking method of chemical liquid film: The appearance of film should be from light grey to dark grey film with dense crystallization and continuous uniformity. The following defects are allowed: slight water marks, chromate marks and slight ash hanging. If there is yellowing and rusting in the film, the film is loose or there is no film on the exposed bottom, and serious ash hanging is not allowed.