Function and Role of Epoxy Mica Intermediate Paint in Protective Coating System

Function and role of epoxy mica intermediate paint in protective coating system
The chemical composition of mica is α-Fe2O3, the content of mica powder is 85%～90%, and the pH is 6.7～7.5. Its flake structure is similar to mica, and the thickness is only μm (one thousandth of a millimeter). The diameter ranges from 0-100 Lun. It has excellent acid resistance, alkali resistance, solvent resistance, high temperature resistance (500℃) and rust resistance, and is non-toxic.
1. The flake mica is evenly distributed in the coating, which can effectively block the penetration of the corrosive medium into the coating, delay the corrosion of the film-forming material and the coated substrate (steel) by the medium, and then improve the anti-corrosion performance of the coating.
2. Due to the effect of flake mica, the surface of the coating film has good roughness, which is conducive to the adhesion of the base coat and the top coat and enhances the adhesion between the layers. The interlayer adhesion of the classic steel structure protective coating system is ≥10 MPa (GB/T 5210).
3. Among synthetic resins, the shrinkage rate of epoxy resin is relatively low (0.3%). Adding flake mica can further reduce the shrinkage rate of the coating.
4. In the long-lasting heavy-duty anti-corrosion coating system, the most important function of flake mica is to resist the damage of light (ultraviolet rays) to the synthetic resin film-forming substance in the coating. Because the light is direct or reflected, once blocked by the cloud iron, it can only be reflected or absorbed. The current long-lasting protective coating system is: zinc-rich primer-epoxy mica intermediate paint-FEVE fluorocarbon topcoat/polysiloxane topcoat/aliphatic polyurethane topcoat.
During the curing process of the coating film, the fluorine atoms migrate and concentrate on the surface of the coating film, playing the role of shielding and protecting the -C-C- bond. Protect it from damage and erosion by ultraviolet light and chemical media. In addition, because the light energy of ultraviolet light is less than the covalent bond energy of fluorocarbon (FC), the ultraviolet light hits the FEVE coating. Except for a small amount of absorption, 95% of the ultraviolet light passes through the FEVE fluorocarbon topcoat (60-70μm). ) It reaches the intermediate coating of epoxy mica, through the shielding and reflection of flake mica, it protects or attenuates the damage and aging of the film-forming material (epoxy resin) by light, and prolongs the service life of the coating system. If flake mica is not used or the content of flake mica in the coating is reduced, the shielding function of the epoxy mica intermediate paint will decrease, which will inevitably accelerate the damage of ultraviolet light and chemical media to the entire coating system.