Corrosion Protection Coatings for Aluminum Aircraft Alloys

The development of corrosion protection coatings for aluminum aircraft alloys is proposed. The coatings are based on polyaniline and other conducting polymers that are incorporated into anodized coatings by oxidative electropolymerization during the anodization process. The coatings will have a two-phase structure with the conducting polymer in the pore volume of the anodic coating. The anodic coating provides a mechanically robust structure that protects the conducting polymer from abrasion while providing a suitable surface for topcoating. A corrosion inhibition mechanism based on adsorption and mobility of the conductive polymers is also proposed for the protection of A1 alloys as well as electrochemial stabilization of the Al oxide surface. To enhance transport and adsorption, and thus corrosion inhibition, the development of a series of modified polyaniline-based polymers and oligomers is proposed. These polyaniline derivatives would be used in Phase I to identify the predominant corrosion inhibition mechanisms and incorporated as polymerizable monomers or oligomers into an acid-based anodization solution. The effect of anodization conditions, conductive polymer doping, and post anodization sealing will be investigated using Al 2024-T3 coupons. Corrosion resistance will be evaluated by DC polarization measurements, zero-resistance-ammeter galvanic coupling experiments, and salt spray exposure of scribed and unscribed anodized coupons.