Hardcoating

HARDCOAT ANODIZING

Hardcoat anodizing (sometimes called hardcoating or hard anodizing) is an electrochemical process that yields an anodic oxide, integral to the aluminum part. Hardcoat anodizing offers a variety of beneficial properties:

Thickness
Corrosion Resistance
Hardness and Wear Resistance
Electrical Resistance
Temperature Resistance
Low Friction Coefficient after Lubrication.

The specific properties of the anodic oxide will be dependent upon the specific alloy being treated and the process parameters being applied.

Like other forms of anodizing (such as Type I Chromic Acid Anodizing or Type II Sulfuric Acid Anodizing), Hard-coat Anodizing (also known as Type III) is produced by immersing the aluminum components into an electrolyte solution. Because the acid bath used for hardcoating is maintained at a cool temperature, there is no risk of thermal or physical distortion of the aluminum parts.

The coating itself is integral to the aluminum component or part. Hardcoat penetrates the base metal as much as it builds up on the surface; the term thickness includes both the buildup and the penetration.

COATING THICKNESS AND SPECIFICATION GUIDELINES

Hard coat anodizing may be provided in thicknesses ranging from a few ten-thousandths of an inch to .008" or .009", depending on the alloy and the application. Like coatings, hardcoat anodizing changes the dimensions of the basic part; although, unlike plating, only half of the hardcoat is buildup (the other half is penetration). For example, .002" hardcoat consists of .001" penetration and .001" added to the original dimension. Therefore, in machining the part, it is essential to allow for the change and to request a specific oxide thickness on blueprints and/or purchase orders.

When developing a hardcoat-anodizing specification, it is important to consult with your anodizer to ensure receipt of a satisfactory product. Consider the following:

The application of the component
Environment of use
The aluminum alloy and temper
Corrosion and hardness requirements
Thickness range of the film
Final dimensional tolerances
Optimum location for contact points (i.e., racking)
Approval requirements and/or other standards.

END-USE APPLICATIONS

Hard-coat anodizing is ideally suited for many product applications. Colors range from light tan to gray/brown, from gold to bronze, and many shades of gray. Various techniques can be employed to enhance the corrosion resistance or abrasion resistance of the treated surface.

Here are just a few examples of hardcoat anodizing applications:

Aerospace
Defense
Energy
Automotive
Marine
Medical
Electronic
Pneumatic
Hydraulic
Chemical
Textile
Bakeware

Hard coat anodizing resists abrading and other environmental degradation, making it the ideal solution for pistons, cylinders, cams, gears, splines, swivel joints, and hydraulic/pneumatic components.

Machine Inc. can help you analyze your hardcoat application possibilities and the solutions available to you.
Feel free to contact us with questions: engineering@machineinc.com

Machine Incorporated
www.machineinc.com
879 Turnpike Street
Stoughton, MA 02072 USA
PH: 781-297-3700
FAX: 781-297-3702 FAX