Given aluminum’s impressive benefits, it’s not surprising that it’s the preferred choice for curtain walls, rainscreens, cladding, roofing systems, window frames and other building and construction applications.
Its lightweight nature—about one-third the weight of steel—combined with exceptional strength can hold its shape under pressure, allowing aluminum to support large glass expanses while maintaining structural integrity. Aluminum’s natural corrosion resistance, thanks to its oxide layer and its flexibility for extrusion into complex shapes make it highly versatile. Additionally, aluminum’s recyclability aligns perfectly with today’s sustainable construction and circular manufacturing goals.
Why Protect Aluminum with Finishes?
While aluminum performs well on its own, applying a protective finish enhances its corrosion resistance, abrasion resistance, UV protection, color options and overall durability. The two most common finishing methods are anodizing and fluoropolymer-based coatings (both liquid and powder). Each offers unique benefits depending on the application and desired aesthetic.
What is Aluminum Anodizing?
Anodizing is a well-established electrochemical process used since the 1960s to enhance aluminum’s natural oxide layer. This multi-step process includes:
- Cleaning to remove dirt, grease and oxides
- Etching, a chemical pretreatment that removes impurities and creates a uniform, matte texture on aluminum to enhance adhesion and appearance
- Immersion in an electrolyte bath with an electric current that thickens the oxide layer
- Adding color to the oxide layer if desired
- Sealing with hot water or steam to lock in color and enhance corrosion resistance
Benefits of Anodized Aluminum:
- Superior corrosion resistance and hardness.
- Embedded color that won’t peel or flake.
- Durable protection against weather, abrasion, UV rays, pollutants and chemicals.
- Sleek metallic finishes ideal for modern architectural designs.
Limitations:
- Limited color range, mostly earth tones and metallics.
- Difficulty achieving bright or custom colors with precise matching.
- Oxide layer brittleness can lead to cracking under impact or bending.
- More costly and time-consuming than some coating alternatives.
- Surface imperfections may become more visible after anodizing.
While anodizing is still widely used in high-performance applications, the process is increasingly being replaced by newer coating solutions that offer attractive advantages in terms of design, durability and application ease.
Liquid Fluoropolymers: A Game-Changer
Until the mid-1960s, anodized aluminum was the go-to standard for durability for metal building elements. That began to change when PPG introduced the first polyvinylidene fluoride (PVDF)-base resin system for architectural metal in 1967. Formulated with 70% PVDF Kynar 500® resins from Arkema and proprietary PPG pigment technologies, DURANAR® liquid coatings were a game-changer that offered a wider palette of solid, mica and metallic finishes, giving greater freedom of expression through color than ever before.
But color is only part of the Duranar value proposition. Meeting FGIA/AAMA 2605 performance standards, the industry’s most rigorous requirements for aluminum performance, Duranar offers unparalleled resistance to UV rays, chemicals, pollutants and weathering. Unlike anodized finishes, Duranar liquid coatings are chemically inert, allowing for longer lasting integrity and colorfastness.
Like the anodizing process, the application of Duranar liquid systems is a multi-step process that, at minimum, consists of a corrosion-inhibitive primer and a durable fluoropolymer color coat. Three-coat systems required for metallic colors include the addition of a clearcoat for added corrosion, weatherability and chemical resistance.
Key Advantages of DURANAR Liquid Coatings:
- Complies with FGIA/AAMA 2605 standards—the highest for aluminum performance.
- Exceptional resistance to UV rays, chemicals, pollutants, and weathering.
- Chemically inert coatings that maintain colorfastness and integrity over time.
- Multi-step application including corrosion-inhibitive primer and durable fluoropolymer topcoat.
- Advanced options like DURANAR SUNSTORM® mica-effect coatings replicate anodized metal’s look with pearlescent flakes and can include solar-reflective or color-shifting pigments.
The Emergence of Powder Fluoropolymers
Emerging in the 1980s, powder fluoropolymer coatings combine the durability of liquid PVDF with the environmental and application benefits of powder coatings. In 2021, PPG launched CORAFLON® PLATINUM, a fluoroethylene vinyl ether (FEVE) powder coating designed for architectural extrusions and sheet aluminum.
CORAFLON PLATINUM Highlights:
- Meets FGIA/AAMA 2605 standards for weathering and corrosion resistance.
- Fast film build with minimal waste and 20% higher transfer efficiency than standard FEVE powders.
- Specifically formulated without TGIC, PFOA, fluorosurfactants, VOCs, HAPs, and LBC Red List substances; REACH-compliant for Substances of Very High Concern (SVHCs).
- Expanded gloss range of 5-85, compared to 25 to 70 for rival FEVE formulations, enabling matte finishes that closely mimic anodized aluminum.
- Long-term colorfastness and corrosion protection unmatched by traditional anodizing.
To Anodize or Not to Anodize
The sleek, modern look of anodized metal remains in architecture as popular as ever. Today, architects, builders and specifiers have more options than ever to achieve that timeless aesthetic. While anodizing offers durable metallic finishes, fluoropolymer coatings provide unmatched color flexibility, design versatility and long-lasting corrosion protection—making them the preferred choice for high-performance architectural and monumental applications.
Advantages of Liquid and Powder Fluoropolymer Coatings
- Easier maintenance and touch-ups.
- Broader color and finish options.
- Outstanding resistance to UV degradation, chalking and fading.
- Enhanced durability against weather, chemicals and pollutants.
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