This technical information has been contributed by
Light Metals Coloring Company Inc.

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The Many Faces of Aluminum

Aluminum Anodizing

According to ALCOA, no other metal can be finished, joined, fabricated, and worked in so many different ways. No other metal is more available in such a variety of forms and textures, and no other metal can be finished by so many methods producing the range of color, inertness, reflectance, and the variety of textures and degrees of surface finish.

Anodizing

Anodizing is an electrochemical process during which aluminum is the anode. The electric current passing through an electrolyte converts the metal surface to a durable aluminum oxide. The difference between plating and anodizing is that the oxide coating is integral with the metal substrate as opposed to being a metallic coating deposition. The resultant surface characteristics coupled with the inherent qualities of aluminum creates a metal of virtually unlimited capabilities. Anodizing services are needed in virtually any industry imaginable. From fashion jewelry and cosmetics, to aerospace; from the medical and military fields to the computer and high-tech electronic industries.

Purpose of Anodizing

There are many reasons to anodize a part. Following are a few considerations and the industries that employ them.

Appearance--Products look finished, cleaner, better and longer. Color enhances metal and promotes a solid, well-built ppearance while removing the harsh metal look. Any aluminum product can be color anodized.

Corrosion resistance--A smooth surface is retained while weathering is retarded. Useful for food handling and marine products.

Ease in cleaning--Any anodized product will stay cleaner longer and are easier to clean when they do get dirty.

Abrasion resistance--The treated metal is tough, harder than many abrasives, and is ideal for caul plates, tooling and air cylinder applications.

Non-galling--Screws and other moving parts will not seize, drag or jam while wear in these areas is diminished. Examples include gun sights, instruments and screw threads.

Heat absorption--Can provide uniform or selective heat absorption properties to aluminum for the food processing industry.

Heat Radiation--Used as a method to finish electronic heat sinks and radiators.

Further, anodizing will not rub off, is an excellent paint base, removes minor scuffs, and is sanitary and tasteless. When aluminum is desirable, but not suitable for an application, the anodizing process many impart a unique combination of properties which make a bad aluminum part good.

Hardcoat Anodizing

As the name implies, a "hardcoat" finish is tough and durable--used where abrasion and corrosion resistance, as well as surface hardness, are critical factors. Essentially, hardcoating is a sulfuric acid anodizing process, with the electrolyte concentration, temperature, and electric current parameters altered to produce the hardened surface. At Light Metals, after years of research and process modifications, hardcoated surfaces have undergone rigid and certified testing with significant results: wearing qualities have actually proven to be superior to those of case hardened steel or hard chrome plate. (The standard test for wearing quality is the Taber Abrasion Test, which measures weight loss.) Results with our hardcoat show the weight loss to be 75 percent less than the allowable standard, indicating superior wearing quality. Moreover, a continuous 1,000 hour salt spray test on anodized marine components was survived without failure, while surface hardness proved to be superior to some steels, registering up to 65 on the Rockwell C scale.

Bulk Anodizing

Bulk anodizing is a company specialty. By modifying standard procedures and creating new ones, we were able to achieve high volume production without sacrificing quality. This is an electrochemical process for anodizing small, irregularly shaped parts which are processed in perforated aluminum, plastic or titanium baskets. The tremendous quantity of parts that can be finished in relatively short time makes this technique highly economical. Another advantage in processing such large volumes at one time is the resulting consistency in color and quality. Finishing items such as rivets, ferrules, medical hubs, etc. using the bulk process make production economically feasible. As many as 2,000,000 small parts per day--with consistent quality and color--have been processed by our firm. Rack anodizing is the traditional means of processing aluminum parts. An on-site rack fabrication department gives us the flexibility needed to meet unique requirements. Rack processing quantities range from a single part to tens of thousands on a single shift.

Sulfuric Acid Anodizing

This is the most common method of anodizing: The part is subjected to a specified electric current through a sulfuric acid electrolyte, converting the surface to an aluminum oxide coating capable of absorbing dyes in a wide range of colors. Abrasion and corrosion resistance are enhanced, and the surface may also be used as a base for applied coatings, such as paint, Teflon, and adhesives. Custom coloring is available to meet any specification, and through pre-finish techniques, matte, satin or highly reflective surfaces can be furnished.

Light Metals Coloring Company has specialized in chemically finishing aluminum parts since 1945. One major corporate achievement was the breakthrough in bulk anodizing. This high-speed, high volume production method reduces finishing costs on thousands of items. It also brings the benefits of aluminum to products that otherwise would have to be made from less durable materials. Many MIL specifications and AMS standards can be met.

This technical information has been contributed by
Light Metals Coloring Company Inc.

Click on Company Name for a Detailed Profile

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