What Is Is Hard Anodizing?

Aluminum is a $40 billion industry in the United States. From transportation to packaging to construction materials, the aluminum industry affects virtually every sector of the economy. In addition its basic applications, aluminum has the unique ability to undergo an electrochemical process called anodizing which gives it an exceptionally hard finish for industrial purposes. A specialty process called hard anodizing goes a step further giving aluminum an outer casing that is harder than any substance known to man other than diamonds.

Identification

Hard anodizing is also known in the industry as a hardcoat. Hardcoat is produced during an electrochemical process that creates a layer of aluminum oxide on exposed surfaces of the base aluminum. The thickness of this hardcoat can be manipulated to strict standards based on the application for which it is needed. Typically, hardcoat is 30 percent thicker than the original aluminum, making it extremely tough, corrosion resistant, machinable and durable.

Appearance

Even though the anodizing process results in a hardcoat that is extremely hard, it is also quite porous. This allows for the application of dyes and other treatments that can give the resulting aluminum a number of different finished appearances. Hard anodized aluminum can take on the physical look of such metals as pewter, stainless steel, silver, gold, copper, bronze or brass. Some dyes can produce hardcoat in a variety of colors, from blue to red.

Production

Standard anodizing is typically accomplished through one of two methods--batch anodizing or continuous coil anodizing. These processes involve applying a series of chemical treatments to the aluminum, which makes the material suitable for use in manufacturing everyday items such as cookware, cosmetic cases and light fixtures. Hard anodizing, however, requires a special set of circumstances. The aluminum is anodized very low temperatures, using high electrical current and specific electrolytes. The resulting hardcoat aluminum is used in industries that need a metallic surface that can stand up to extreme wear and tear such as the infrastructure of skyscrapers like the Sears Tower, automotive engine parts like pistons and hydraulic gears and components of the space shuttle.

Specialty

Hard anodizing is a process that is typically conducted only by specialty companies with the equipment and expertise required. Because the process of hard anodizing is exceptionally predictable, the thickness of the coating, electrical conductivity, wear and temperature resistance, and other factors can be closely controlled to meet the specific needs of the individual end user. Industries that operate in extreme conditions, such as the military in desert situations, or communications satellites in outer space, need the toughness provided by the hard anodizing process.

Application

Hard anodized aluminum has applications in numerous commercial and high-tech industries, including military and defense, aerospace, construction, electronics and home cookware. The ultra-hard finish allows for commercial building applications such as elevator doors, escalators and staircases that require little maintenance yet still maintain their beauty. The hard anodizing production process is also considered to be ecologically sound, with little or no impact on the environment.

Resources

• The Aluminum Association