Selection of coating thickness of ppgi steel roll

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The level of corrosion resistance of color coated ppgi steel roll is closely related to the thickness of the coating, which usually increases with the thickness of the coating. The appropriate coating thickness should be determined according to environmental corrosion, service life, and durability.

Color coated ppgi steel rolls are composed of a substrate and a colored web or plating. We first have to consider the thickness of the substrate and web coating, the better color-coated steel substrate is 0.02~0.05mm, and the thickness of the compound film or coating is often only 0.15mm or less. Because of the influence of color coated ppgi steel roll's use time, the thickness of the substrate is very important. And some manufacturers who produce color steel plate tend to do tricks on the substrate and color steel plate coating or compound film, they reduce the thickness of the substrate but increase the thickness of the peritoneum to reduce the production cost of color coated ppgi steel roll, which greatly reduces the service life of color steel roll.



Microscopically speaking, the coating is a multi-empty organization. Water in the air, a corrosive medium (chloride ion, etc.) will invade through the weak part of the coating, causing corrosion under the film, and then the coating blisters and peels off. In addition, even if the same coating thickness, the secondary coating is denser than the primary coating. According to foreign reports and related corrosion test results, frontal coating of more than 20μm to effectively prevent the intrusion of corrosive media, due to the primer and top coat corrosion prevention mechanism is different, not only to specify the total film thickness, there are separate requirements for the thickness of the primer (≥ 5μm) and top coat (≥ 15μm), only in this way, to ensure that the color coated ppgi steel roll different parts of the corrosion resistance is balanced.

PVDF products require a thicker coating film because of the need to provide a longer service life guarantee. The requirements for the back coating depend on the application, sandwich panels require only one layer of bondable primer, while formed steel sheets also require two layers of at least 10μm thickness due to the corrosive indoor environment.