Industrial Hard Coat Anodizing
As a raw metal, aluminum has wonderful properties of ductility and malleability, but these very characteristics also means that it is very soft. Industrial hard coat anodizing deposits a thick layer of aluminum oxide both on and in the surface of the aluminum, resulting in a surface hardness approaching that of diamonds.
Industrial hard coating is a Type III anodizing process, utilizing low bath temperatures, high current density, special electrolytes, and agitation to form a very hard, thick coating of aluminum oxide that actually penetrates the surface of the base metal. In fact, in true hard coat anodizing, fully half the thickness of the protective aluminum oxide layer penetrates beneath the surface, with the other half building up above the surface.
Industrial hard coating will result in an aluminum piece that exhibits superb abrasion and wear resistance, with excellent dielectric properties. Hard coat anodized surfaces also have a high degree of lubricity, which can be further enhanced by impregnation with solid lubricants such as PTFE (Teflon®) for an even lower coefficient of friction.
It has long been known that reactive metals and alloys can be protected from corrosion and deterioration by the application of of a coating of an unreactive material. Such a protective coating can greatly extend the use of the metals and alloys. In the case of aluminum, the development over the past two decades of hard anodizing has permitted uses of the metal far beyond those envisioned by its discoverers. Because hard anodizing prevents galvanic reaction, aluminum can now be used with steel, brass, and bronze.
Industrial Hard Coat Anodizing (Type 3/Type III) is not to be confused with ordinary anodized aluminum, in which a very thin coating of aluminum oxide is developed only on the surface of the metal. Hard anodizing requires a special electrolysis process which produces a dense layer of aluminum oxide BOTH ON and IN the aluminum surface. The thickness of this hard anodizing coating ranges from 1 to 3 mils or more.
Aluminum oxide is an inert, stable compound. As a coating, it imparts this inertness to the aluminum surface. Because it distributes heat evenly and efficiently, it can be used as a coating of high temperature material for industrial furnaces.