Corrosion Protection of Aluminum and its Alloys Using Electroactive Polymers

The AFOSR funded program was designed to specifically test the ability of electroactive polymers, especially polyanilines, to provides corrosion protection for aluminums, especially the copper approximately 4 to 5 containing AA2024-T3 alloy of key interest to the Air Force. This program demonstrated the anti-corrosion capability of polyaniline coatings on aluminum alloy 2024-T3. In particular, undoped emeraldine base, fully sulfonated polyaniline NSPAN, and undoped trimer coatings on AA2024-T3 were shown to reduce pitting in argon deaerated 0.1M NaCl using potentiodynamic polarization studies. The corrosion potential was shifted to more noble, and corrosion current was reduced 100- to 1000-fold in pH - 3 environments. The anti-corrosion capability of emeraldine base polyaniline coatings of AA2024-T3 in 0.1M NaCl further was been demonstrated by X-ray photoelectron spectroscopy XPS depth profiling which showed a clear depletion of Cu for - 500 A. Visual inspections demonstrated the effectiveness of sulfonated polyaniline solutions at preventing corrosion of aluminum and iron alloys. A new mechanism of corrosion reduction in aluminum alloys different from that operative in ferrous alloys was proposed, i.e., copper depletion by an active polymer such as polyaniline at the corroding surface.