Advantages of Hard Coating
Hardcoat anodizing (also know as Hard Anodizing, Hard Coating, and Type III Anodizing) exceeds wear characteristics of other hard coatings such as electroless nickel, hardchrome, and ceramic. The hardcoat anodizing process produces superior hardness and denseness - when a part is hardcoated, it increases the micro finish 2-5 times, depending on the alloy.
Advantages of Hardcoat anodizing include:
- Unmatched wear properties
- Coatings wear as well as or better than hardened steels (HRC values of 70) as judged by Suga and Taber Wear tests
- Can achieve salt spray resistance in excess of 1000 hours
- Good for salvage work of parts with critical dimensional specifications
- High dielectric strength to 2000 VDC
- Heat dissipation
Taber abrasion testing shows that Hard Coating exceeds wear characteristics of other hard coatings such as electroless nickel, hardchrome, and ceramic.
Some industrial applications of Hardcoat anodizing include highly intricate parts such as pistons, anti-lock brake assemblies, pump components, valves, sliding parts, insulation plates and transmission parts. Some retail applications for Hardcoat anodizing and Sulfuric anodizing include cookware, bike rims, locks and levels.
Recent developments, such as lubricity, have added a new dimension to the successfully hardcoated product without altering the tolerances of the Hardcoated part. When a customer requires a finished piece that will be subject to friction under close tolerance conditions and where a solid film lubricant would cause problems, a lubricant after the hardcoating process could be the answer.
Salvage Through Hardcoating
The use of hardcoat for salvage operations has proven very successful. Parts rejected because of bores that have been machined oversized are being hardcoated and honed to become acceptable parts. Wrought and cast alloys both lend themselves to salvage operations, but the hardcoat thickness that can be applied is governed by the alloy of the salvage part. Salvage through hardcoat pays off. A prime example is in the aircraft industry, where parts costing thousands of dollars to machine are being salvaged by hardcoating the oversized bores.
The final appearance of a hardcoated surface depends on the alloy and thickness of the coating. The color of an undyed finish can range from gray to black and various shades of bronze can be produced. If close tolerances aren't a factor, Bright Dip will improve the appearance of the finish.
Hard coat should not be sealed where the main function of the application is to obtain the maximum degree of abrasion or wear resistance. Where Hard coatings are used for exterior non-maintained applications requiring corrosion resistance but permitting reduced abrasion resistance, sealing is available. Sealing of Hard Coat can be accomplished by immersion in a medium, such as boiling deionized water, in a hot aqueous 5 percent sodium dichromate solution, in a hot aqueous solution containing nickel acetate or other suitable chemical solutions.
Hard Coat that does not require a seal should be thoroughly rinsed in cold, clean water and dried after anodizing.
Alloys and Castings:
The Effects on Hardcoat Anodizing
The final appearance of a hardcoated surface depends on the alloy and thickness of the coating. The color of an undyed finish can range from gray to black and various shades of bronze can be produced. If close tolerances aren't a factor, Bright Dip Anodizing will improve the appearance of the finish.
Over 200 aluminum alloys, each with up to eight different tempers or hardness values, are available. Each alloy and temper displays unique characteristics with respect to anodic films that can be formed.
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