Plating
Coating thickness is the most important guarantee condition for corrosion resistance. The larger the coating thickness, the better the corrosion resistance, which has been proven by many accelerated tests and nasal exposure tests.
As shown below:
For color steel plates based on (aluminum) zinc plated plates, the coating thickness mainly affects the notch corrosion performance of color steel plates. The thinner the substrate, the thicker the zinc layer, and the better the corrosion resistance of the cut. It is currently recognized internationally that zinc ratio ≥ 100 is an effective protection against notch corrosion of color coated steel plates
Certificate. Taking a 0.5mm substrate as an example, the plating content per square meter on one side should reach at least 50g.
How to choose the type of coating
The main role of the coating is reflected in both visual effects and protective functions. The pigments of the coating can be divided into organic pigments and inorganic pigments, with bright colors and luster; Inorganic pigments are generally light colored, but their chemical properties and UV resistance are superior to organic pigments.
The most commonly used topcoats for colored steel plates include polyester (PE), silicon modified polyester (SMP), high durability polyester (HDP), and polyvinylidene fluoride (PVDF). Each topcoat is suitable for different situations, and we recommend using HDP or PVDF products when economy permits.
For the selection of primer, epoxy resin should be selected if adhesion and corrosion resistance are emphasized; For more attention to flexibility and UV resistance, choose polyurethane primer.
For the back coating, if the color coated steel plate is used as a single plate, select a two-layer structure, that is, one layer of back primer and one layer of back finish. If the color coated steel plate is used as a composite or sandwich plate, a layer of epoxy resin is applied on the back.
Effect of coating thickness on service life
The colored steel plate coating can play a certain role in corrosion prevention, using the coating film to isolate external corrosive substances. However, due to the microscopic appearance of the coating film itself, there are still pores, and a small amount of water vapor in the air will still invade the coating, causing blistering of the coating and possibly causing the coating film to fall off. For steel plate, plating
The layer (zinc plated or aluminum zinc plated) has a greater impact on the life of the steel plate.
For the same coating thickness, the secondary coating is denser than the primary coating, with better corrosion resistance and longer service life. For coating thickness, based on the relevant corrosion test results, we recommend that the front coating be 20 um or more, as sufficient film thickness can prevent corrosion within the validity period
Prevent the occurrence of corrosion (PVDF requires a thicker coating thickness due to longer service life requirements, typically 25 μ M or more).
Post time: Mar-31-2023