ABSTRACT
Chromic acid anodize produces an inert layer of aluminum oxide on the surface and is an effective means for retarding bond line corrosion. Sealed chromic acid anodize has been used successfully for a number of years in the production of adhesive-bonded assemblies. The sealed chromic acid anodize process employs solutions that contain strong acids and hexavalent chromium compounds. Sealed chromic acid anodize may be used effectively with both corrosion-inhibiting adhesive primers and non-corrosion-inhibiting primers. Sealed chromic acid anodize may be employed as a surface preparation for use with any adhesive system normally used to bond aluminium. The appearance of the chromic acid anodize coating will vary with the alloy and type of surface. Although visual inspection of an anodic coating cannot be used to determine bondability, it is an important and necessary tool for routine process control after bondability has been established. Chromic acid anodize produces a characteristic gray color on most aluminum alloys.
