polyaniline coatings on aluminum or copper

Our approach is centered on the chemistry of metal passivation.  Passivation is the process in which particular metals, when placed in oxidizing conditions, spontaneously form metal-oxide coatings that slow the rate of oxidation and thereby protect the metals.  Stainless steels and alloys of titanium or aluminum are corrosion-resistant because of their oxide surfaces.

Electrochemically-active polymer coatings, such as those formed by polyaniline, enable certain active-passive metals to become more resistant to oxidation, apparently by enhancing their native passivity.  Polyaniline applied in the emeraldine state is reduced by substrate metal to leucoemeraldine state; reaction of leucoemeraldine with air restores the polymer's emeraldine oxidation state.

Oxidation-reduction chemistry between substrate metal and polyaniline results in a more noble, better passivated metal surface.

Literature:

H. Letheby, J. Chem. Soc. 1862, 15, 161

D. W. DeBerry, J. Electrochem. Soc. 1985, 132, 1022

B. Wessling, Advanced Materials 1994 6, 226