Fluorocarbon Sprayed Aluminum Baffles: Technical Standard Analysis of Outdoor Weather Resistance

Fluorocarbon sprayed aluminum baffles are the first choice for outdoor architectural decoration. Their core performance comes from the fluorocarbon coating on the surface. This coating based on polyvinylidene fluoride (PVDF) resin has excellent weather resistance, corrosion resistance and chemical resistance, and can maintain stable color and performance for a long time in harsh outdoor environments. It is the best surface treatment method for metal decorative materials with weather resistance at present. However, many products labeled as "fluorocarbon spraying" on the market are actually pretended by polyester spraying or powder coating. Their weather resistance differs by several times, and the price also differs by 30%-50%. Buyers need to understand the technical standards and identification methods of fluorocarbon coatings to avoid being deceived.

Real fluorocarbon sprayed aluminum baffles use fluorocarbon coatings with polyvinylidene fluoride (PVDF) content not less than 70%, and must adopt three-coat two-bake production process. The coating structure is divided into three layers: the first layer is primer, with thickness of 5-10μm, which functions to improve the adhesion between the coating and aluminum substrate and has anti-corrosion effect; the second layer is color paint layer, with thickness of 25-30μm, which is the layer that provides color and main weather resistance, and PVDF resin is mainly concentrated in this layer; the third layer is varnish layer, with thickness of 10-15μm, which functions to protect the color paint layer, improve the surface hardness, stain resistance and UV resistance of the coating. The total coating thickness is controlled between 40-55μm. Fake fluorocarbon products on the market usually adopt two-coat one-bake process, without varnish layer, the total thickness is only 20-30μm, or use fluorocarbon coatings with PVDF content less than 30%, whose weather resistance cannot be guaranteed.

There are three main technical standards for fluorocarbon coatings: American AAMA 2605 standard, Chinese GB 5237.5 standard and European Qualicoat standard. Among them, AAMA 2605 is the most stringent fluorocarbon coating standard at present, requiring the coating to pass at least 10 years of outdoor exposure test, or after 4000 hours of accelerated artificial weathering test, the gloss retention rate is not less than 80%, the color change ΔE is not more than 5 units, no chalking, cracking, blistering, falling off and other phenomena, and at the same time pass 3000 hours of salt spray test, 100 times of scrub resistance test, acid and alkali resistance test, etc. Fluorocarbon coatings meeting AAMA 2605 standard can guarantee no fading, chalking or falling off for more than 20 years of outdoor use. Chinese GB 5237.5 standard is divided into superior products and qualified products. Superior products require 2000 hours of artificial aging test to be qualified, corresponding to more than 15 years of service life; qualified products require 1000 hours of artificial aging test to be qualified, corresponding to more than 10 years of service life. When purchasing fluorocarbon aluminum baffles for outdoor use, at least meeting the GB 5237.5 superior product standard is required, and important projects require meeting AAMA 2605 standard.

The core performance indicators of fluorocarbon coatings include: adhesion, tested by cross-cut method to reach level 0, that is, the coating does not fall off at all; pencil hardness reaches above H, with good scratch resistance; impact resistance reaches 50kg·cm, the coating does not crack or fall off; salt spray resistance, after 4000 hours of salt spray test, the coating has no change, and corrosion spread at the scribed line does not exceed 2mm; accelerated artificial weathering resistance, after 4000 hours of QUV aging test, gloss retention rate ≥80%, color difference ΔE≤5; stain resistance, the surface contamination rate of the coating is not more than 5%, easy to clean; chemical resistance, resistant to 10% hydrochloric acid, 10% sodium hydroxide, detergents and other chemical substances, the coating has no change. These performance indicators require test reports issued by third-party authoritative testing institutions as proof. When purchasing, manufacturers must be required to provide test reports within the past six months, not reports from several years ago or copies.

There are several simple ways to identify true and false fluorocarbon coatings: first, look at the price. The processing fee for real three-coat two-bake fluorocarbon spraying is 60-80 yuan per square meter. Adding the cost of aluminum substrate, the price of fluorocarbon aluminum baffles cannot be more than 30% lower than polyester spraying products. If the price is significantly lower than the normal market price, it can basically be judged as a fake product; second, look at the surface. Real fluorocarbon coating has delicate and smooth surface, strong metallic texture, transparent and bright varnish layer, polyester coating has relatively dim surface and poor metallic texture, powder coating surface has slight orange peel phenomenon; third, test hardness. Draw on the coating surface with an ordinary pencil. The hardness of fluorocarbon coating reaches above H, and HB pencil will not leave traces. The hardness of polyester coating is only about B, which is easy to leave traces; fourth, look at the test report. Regular fluorocarbon coating suppliers such as PPG, AkzoNobel, Nippon will issue coating quality certificates to manufacturers using their coatings, and manufacturers can be required to provide coating purchase vouchers and manufacturer's quality guarantees.

Fluorocarbon sprayed aluminum baffles are mainly used in decoration projects such as building exterior walls, outdoor ceilings, awnings, sunshade systems, and high-corrosion environments (seaside, chemical plant areas). Seaside projects have high salt spray content in the air and strong ultraviolet rays, so high weather resistance fluorocarbon coatings meeting AAMA 2605 standard must be used, and the coating thickness is not less than 50μm; chemical plant areas have corrosive gases such as acid and alkali in the air, so high-grade fluorocarbon coatings must also be used; exterior wall projects in ordinary inland areas can use fluorocarbon coatings meeting GB 5237.5 superior product standard. It should be noted that even fluorocarbon coatings will not completely change color. Dark and bright fluorocarbon coatings will have slight color changes after long-term outdoor use, which is a normal phenomenon. As long as the color difference is within the allowable range of the standard, it is a qualified product; light color fluorocarbon coatings such as light gray, white, silver have better color stability and are more suitable for large-area exterior walls.

In terms of construction and maintenance, attention should be paid to protecting the coating when installing fluorocarbon aluminum baffles to avoid hard object scratches. After installation, the surface protective film should be torn off in time, and the surface stains should be cleaned with neutral detergent. Do not use strong acid and alkali detergent to clean to avoid damaging the coating. The maintenance cycle of fluorocarbon coating is very long, generally cleaning once every 5-10 years, no special maintenance is required, and the service life can reach more than 20 years under normal use.