Electrochemical behavior of mild steel coated by polyaniline doped with organic sulfonic acids

A comparison of electrochemical behavior was made of coatings of pure undoped PANI cast from solution and this coating after doping as a film on the substrate. These were also compared to coatings of pure PANI/sulfonic acids adducts formed from the outset in the doped state through casting from xylene or chloroform solutions. The results obtained allowed to assume that the formation of protective iron oxide layers occurs mainly during the coating of pure undoped PANI (emeraldine base). During the doping stage a modification of these layers obviously proceeds leading to a change of the corrosion currents of the whole coating system. As a consequence, the formation of pure doped PANI coatings by casting doped PANI from solutions cannot give as good of results as does the two stage process.