Chromic Acid Anodize

What is Chromic Acid Anodize?

Chromic acid anodizing or type I anodize results in the thinnest anodic coat of the principal three types; typically on the order of .00002”-.0001” (20 to 100 microinches) per surface. While thin, when properly sealed chromic anodize affords the aluminum equal corrosion protection to the thicker sulfuric and hardcoat type anodize.

How is Chromic Acid Anodize different from other types of anodize?

Chromic anodize appears much grayer in color and being thinner absorbs less color when dyed. This limits chromic acid anodize as a decorative finish, however, it can be dyed black for use as a non-reflective, protective coating on housings for optical components. Even black dyed chromic anodize is lighter in appearance (grayer), than conventional sulfuric black anodize. In order to get chromic anodize to accept black dye, the temperature of the chromic acid must be raised, therefore, it isn’t done every day and must be scheduled accordingly.

What are the attributes / characteristics of Chromic Acid Anodize?

  • Good for tight tolerance parts: will not change dimensions
  • Can be black dyed - other colors not practical
  • Good for Bonding
  • Non-Conductive
  • Good for welded parts and assemblies

What are some applications of Chromic Acid Anodize?

  • Precision Machined Components
  • Aerospace Components
  • Welded components and assemblies
  • As a paint/prime base