What is Anodizing?
Anodizing is an electrochemical conversion process in existence since the 1930’s. Several metals are capable of being anodized including aluminum, magnesium, titanium, and tantalum. Anodized aluminum is used in many applications due to its low cost, aesthetic qualities and ideal mechanical properties.
Unlike most protective coatings, anodizing permanently changes the outer structure metal. When aluminum is exposed to air it naturally develops a think aluminum oxide film that seals the aluminum from further oxidation. The anodizing process makes the oxidized surface much thicker, up to several thousandths of an inch thick. The hardness of the anodized aluminum oxide coating rivals that of a diamond, enhancing the abrasion resistance of the aluminum. The added depth of the oxide layer improves the corrosion resistance of the aluminum, while making cleaning of the surface easier. The porous nature of particular types of anodizing makes it possible to dye the aluminum a variety of colors, making it more attractive.
Sulfuric anodizing is the most common method of anodizing, utilizing sulfuric acid to yield coatings up to 1mil (25 microns) thick. 67% penetration into the substrate and 33% growth over original dimensions occurs. Due to its permeable nature, sulfuric anodizing is excellent for color dyeing and provides a base for primers, bonding agents and organic coatings. Sulfuric anodizing provides corrosion resistance and is very durable. Typical applications include architecture, aerospace, manufacturing automotive and computers.
Why Anodize?
Anodizing is a highly effective and desirable mean of finishing aluminum. Some of the primary advantages of anodizing include:
- Durability- Most anodizing parts experience no wear from handling, installation, usage and maintenance adhesion-Anodizing is part of the aluminum for total bonding and unmatched adhesion.
- Color- Anodized parts maintain good color stability when exposed to ultraviolet rays, do not have an applied coating that is subject to chipping or peeling, and have a repeatable coloring process.
- Quality of original finish- Parts are not subject to marking from the original anodizing process.
- Maintenance- Mild soap-and-water cleaning usually will restore an anodized profile to its original appearance.
- Aesthetics- Anodizing offers a large number of gloss and color alternatives, while allowing the metallic appearance of the extruded aluminum to show through.
- Cost- Anodizing is a very cost-effective value compared to other finishing methods. In addition to low processing and maintenance costs, durability minimizes replacement costs.
- Environment, health and safety- Anodizing is favorable towards current environmental regulations because it is one of the most environmentally friendly industrial processes and is typically not harmful to human health. An anodized finish is chemically stable, will not decompose, is nontoxic, and is heat-resistant to the melting point of aluminum. Since the anodizing process is a reinforcement of a naturally occurring oxide process, it is non-hazardous and produces no harmful or dangerous by-products. Chemical baths used in the anodizing process often are reclaimed, recycled, and reused.