Reasons for Selecting White Fused Alumina (WA) Micropowder for Ceramic-Type Fluorocarbon Powder Coatings
1. Superior Whiteness (Distinction from Green Silicon Carbide, GC)
White Fused Alumina is a pure white powder with an Al2O3 content exceeding 99%. It contains minimal impurities and negligible iron, ensuring that it does not impart a green, black, or yellow tint to the coating. This allows for the accurate formulation of light-colored fluorocarbon coatings—such as silver, off-white, and light gray—which are commonly used in architectural applications. In contrast, Green Silicon Carbide is a green powder, limiting its use to dark-colored coatings and making it unsuitable for the light-colored fluorocarbon finishes typically applied to aluminum panels. Brown Fused Alumina, due to its high iron content, is prone to rusting and discoloration, and is therefore generally avoided in outdoor fluorocarbon coatings.
2. Enhanced Hardness, Scratch Resistance, and Wear Resistance (“Ceramic-like” Effect)
With a Mohs hardness of 9, White Fused Alumina creates a rigid internal framework within the coating. This boosts the pencil hardness of the coating to a range of 4H–7H, providing resistance against erosion from wind-blown sand and scratches from hard objects. This is the origin of the term “ceramic-type” fluorocarbon powder; conventional fillers—such as calcium carbonate, talc, or quartz powder—lack sufficient hardness and offer significantly inferior wear resistance.
3. Weather Stability and Suitability for Long-term Outdoor Fluorocarbon Applications (AAMA 2605 Standard)
White Fused Alumina is chemically inert and highly resistant to UV radiation, salt spray, acids, and alkalis. It does not chalk under prolonged outdoor exposure, nor does it react with the fluororesin, thereby preserving the inherent 20+ year durability of the fluorocarbon coating. Many other hard fillers are prone to discoloration or degradation when exposed to UV light, making them unsuitable for high-end architectural fluorocarbon systems.
4. Compatibility with High-Temperature Curing Processes
Fluorocarbon powder coatings require curing at high temperatures, typically between 180°C and 220°C. With a melting point exceeding 2050°C, White Fused Alumina remains stable during the baking process—it does not decompose, discolor, or cause blistering—demonstrating excellent thermal stability.
5. Well-suited for powder processing: offers excellent dispersion and low oil absorption.
With controllable particle size and a narrow particle size distribution, its low oil absorption prevents excessive adsorption of fluororesin. This facilitates easier formulation, ensures smooth extrusion and granulation, and promotes stable leveling during spraying—minimizing defects like pinholes and “orange peel.” Furthermore, the angular particles create a mechanical interlock with the resin, enhancing coating adhesion and density, while improving water and corrosion resistance.
Advantages of white fused alumina (white corundum) micropowder as a filler for ceramic-type fluorocarbon powder coatings, compared to other wear-resistant materials:
· White fused alumina: White in color, with excellent wear resistance and superior weatherability → Ideal for light-colored or silver-toned ceramic fluorocarbon powder coatings.
· Green silicon carbide: Green in color, with higher hardness and superior wear resistance; however, its color limits its application → Restricted to dark-colored, wear-resistant coatings.
· Quartz powder: White, but possesses low hardness, offering only limited improvement in wear resistance.
· Brown fused alumina: Brownish in color and contains iron, which can lead to rusting and discoloration; unsuitable for outdoor fluorocarbon coatings.