CORROSION PROTECTION USING POLYANILINE COATING FORMULATIONS

Growing environmental concerns regarding the use of heavy metals in co ating formulations has led to a new coating strategy employing inheren tly conducting polymers (ICP) as a key component. ICPs (such as polyan iline, polypyrrole and polythiophene) are electrically conductive owin g to a system of conjugated double bonds. Observations of metal passiv ation complement this conductive nature and offer a viable alternative to traditional corrosion protection (1-8). A key potential advantage that the ICP coating technology offers is toleration of pin holes and minor scratches. The basis for this argument is that, since the ICP co ating is conductive, the entire coating acts to passivate any areas of exposed metal. This paper describes a model for polyaniline (PANI) co rrosion protection and presents data which clearly demonstrate signifi cant corrosion protection in a salt fog environment. ESCA and electroc hemica data are presented which show that an Fe-PANI complex is formed in the process of coating steel with PANI. The Fe-PANI complex is sho wn to catalytically reduce oxygen. Preliminary electrochemical impedan ce results are also presented which show an additional time constant a t 20 kHz, which appears to correlate with the effectiveness of PANI to ward corrosion protection.