Epoxy resin has strong adhesion and good adhesion to most substrates; it has good physical and mechanical properties and excellent chemical resistance. When used with glass flake pigments, the glass flake epoxy coating produced is very suitable as a substitute for the currently commonly used mica-iron epoxy intermediate paint. Through the practical experience of bridge painting in the UK (such as ForthRailBridge, TayRail, etc.), the zinc-rich primer is not used, but the anti-corrosion properties of the glass flake epoxy coating are relied solely on, and the expected results are achieved.
Glass flake polyester coating has good chemical resistance, cathodic stripping resistance, and high wear resistance. It is widely used in ship painting, especially for deck channels, decks, icebreaker hulls, etc. Due to its chemical resistance and solvent resistance, glass flake vinyl ester coating has higher chemical resistance and better alkali resistance than polyester coating when used on the inner wall of storage tanks.
The thickness of glass flakes is generally 2~5μm. The dry film thickness of general solvent-based glass flake epoxy coatings reaches 200~400μm, and there can be dozens to hundreds of layers of flakes arranged in the coating, forming a complex and tortuous anti-penetration diffusion path in the coating.
Glass flakes divide the coating into many tiny spaces, dividing the micro-cracks and micro-bubbles in the coating. The shrinkage rate of the glass flakes is a fraction to a few tenths of that of the resin. During the curing process of the coating, it can reduce the shrinkage stress of the coating and improve the adhesion of the coating. It also suppresses defects such as cracking and peeling of the coating, allowing a thicker coating to be obtained by single-pass spraying.
The anti-corrosion mechanism of glass flake anti-corrosion coating is similar to the role of aluminum powder and cloud iron in the coating. It achieves the anti-corrosion effect by changing the diffusion and penetration route of the corrosive medium (such as air, water, acid, and alkali etc.), making it difficult for it to penetrate the substrate.
Using glass flake anti-rust pigments, the fish scale effect, composed of multiple layers of glass flake pigments arranged approximately parallel to the base material, can extend the penetration distance of corrosive media several times or even dozens of times. Generally, the larger the diameter of the glass flakes, the stronger the anti-penetration performance of the coating, but the appearance of the coating is relatively poor.
Generally, glass flakes of different diameters are mixed to achieve the effect that the larger diameter glass flakes are arranged parallel to the substrate, and the smaller diameter glass flakes are interspersed in the gaps at different angles.
When used as a topcoat, more glass flake pigments with smaller flake diameters are used to obtain a flatter coating.
Treating glass flake pigments with silane coupling agents can improve their strength and bonding with film-forming resins. For coatings, their wear resistance and penetration resistance can be improved.
