HARD ANODIZING, also known as type III anodizing, is a thicker and harder form of anodizing. This process produces a dense, hard, and wear-resistant oxide layer on the surface of the aluminum, which provides improved protection against corrosion and abrasion.
Type III hard anodizing is a specific type of hard anodizing process used to produce a hard and durable surface layer of aluminum oxide on aluminum alloys. The process typically involves the following steps:
- Cleaning: The surface of the aluminum substrate is thoroughly cleaned to remove any contaminants.
- Iridite Pretreatment: The aluminum surface is treated with Iridite, a proprietary chromate conversion coating, to improve adhesion and corrosion resistance.
- Anodizing: The aluminum substrate is immersed in a sulfuric acid electrolyte and an electrical current is applied, causing the aluminum surface to oxidize and form a layer of aluminum oxide.
- Thickness Control: The thickness of the anodized layer is controlled by adjusting the applied voltage, time of exposure to the electrolyte, and temperature of the electrolyte. The typical thickness of Iridite hard anodizing Type III is between 20-30 microns.
- Sealing: The anodized surface is then sealed to prevent further oxidation and improve corrosion resistance.
- Post-Treatment: The anodized parts may undergo additional post-treatment processes, such as coloring or surface finishing, to improve appearance and performance. Iridite hard anodizing Type III is commonly used in aerospace, defense, and industrial applications for its high wear resistance, low friction, and excellent corrosion resistance.