On the mechanism of corrosion protection of mild steel with polyaniline

The protective capacity of solution-cast polyaniline coating systems toward mild steel has been investigated via simple electrochemical polarization techniques. Coatings containing a polyaniline-emeraldine salt species were found to significantly reduce corrosion rates in 0.1 mol dm(-3) NaCl and 0.1 mol dm(-3) HCl. The nonconducting counterpart, polyaniline-emeraldine base, also provided some degree of protection in the latter medium. Most importantly, the data confirms that an anodic protection scheme cannot operate in such media. The results presented herein support the emerging paradigm that protection stems from the inhibitory properties of the polymer's dopant species. (C) 2004 The Electrochemical Society.