From a microscopic point of view, there are many pinholes in the coating, and the size of the pinholes is enough to allow external corrosive media (water, oxygen, chloride ions, etc.) to penetrate into the substrate, and u nder a certain relative humidity, a filamentous corrosion phenomenon occurs. The thicker the coating, the fewer pinholes, and the better the corrosion resistance of the substrate. As shown in the figure, different coating thicknesses affect the corrosion resistance. The test results show that when the coating thickness is above 20μm, the corrosion resistance effect is relatively stable.
Coating quality and processing also affect the final corrosion resistance of color coating products. If the light is made of cold rolling base plate (not including plating) directly to MCL, due to the corrosion products of iron loose easy absorption of moisture, and no secondary protection, so its corrosion speed quickly, if a fairly thickness of galvanized zinc (aluminum plating zinc/aluminum magnesium) substrate, it can play the role of “firewall”, will greatly improve the corrosion resistance of products.
Post time: Jun-10-2022