What Is Hard Anodizing?
Hard Anodizing or Hardcoat is an electrochemically produced grey layer of hard aluminum oxide on the surface of aluminum components.
The coating grows integrally with the base metal and is corrosion and wear resistant and machineable.
The thickness can be very closely controlled and be applied to a wide range of parts to suit applications from many industries.
How Is It Produced?
The film is built up by a process of anodic oxidation in a cooled acid electrolyte thus preventing any thermal or physical distortion of precision engineered components.
Secondary treatment such as impregnation with solid film lubricants and coloured dyes are available.
Coating Properties
These are dependant upon alloy type and the process specification will typically give details of:
- Thickness
- Corrosion Resistance
- Hardness and Wear Resistance
- Electrical Resistance
- Temperature Resistance
- Friction Coefficient after lubrication
Coating Quality
Hard Anodizng is a well established process suitable for meeting today's demanding quality requirements.
National and International standards provide a basis for the secification, production and testing of the coating.
To ensure a satisfactory product it is important that the customer works closely with the Anodizer at the specification stage on:
- The application for the component
- The aluminum alloy to be used
- Corrosion and hardness requirements
- Thickness range of the film final dimensional tolerances
- Optimum location for contact points
- Any approval requirements
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During anodizing, the aluminum oxide layer is made thicker by passing a direct current through a sulfuric acid solution, with the tube serving as the anode, the negative electrode. The current releases hydrogen at the cathode, the positive electrode, and oxygen at the surface of the aluminum anode, creating a buildup of aluminum oxide.
Hard Anodizing finishes have an established reputation in a wide variety of applications. Major user industry sectors include:
- Aerospace
- Defence
- Pneumatic
- Hydraulic
- Automotive
- Energy
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- Chemical
- Medical
- Bakewear
- Textile
- Marine
- Electronic
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Aluminum anodizing is the electrochemical process by which aluminum is converted into aluminum oxide on the surface of a part. This coating is desirable in specific applications due to the following properties:
- Increased corrosion resistance
- Increased durability / wear resistance
- Ability to be colored through dying
- Electrical insulation
- Excellent base or primer for secondary coatings
The process of anodizing is rather simple. It consists of an anodizing solution typically made up of sulfuric acid. A cathode is connected to the negative terminal of a voltage source and placed in the solution. An aluminum component is connected to the positive terminal of the voltage source and also place in the solution. When the circuit is turned on the oxygen in the anodizing solution will be liberated from the water molecules and combine with the aluminum on the part forming an aluminum oxide coating.
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