What is the difference between Sulfuric Type II Anodizing and Hard Coat Type III Anodizing?
Hard Anodizing or Hardcoat Anodize produces an oxide coating that is typically thicker and denser than sulfuric acid anodize. Because of the film’s density, it produces a hardness of 60 to 65 Rockwell on the C scale. The color of this film varies from light gray to dark olive gray depending on the material’s alloy, temper and coating thickness. Because of the coating density, it is not as easily dyed and not typically used in cosmetic applications. Wear resistance is the most frequent reason for specifying Hardcoat Anodizing over Sulfuric Anodizing. Hardcoat has excellent dielectric strength and is often used to insulate assembly components. Corrosion resistance is a third reason for using Hardcoat. At normal film thickness of 0.002″, the coating offers corrosion protection superior to that of other anodic coatings, especially when it is sealed.
