A Comparison between Corrosion Protection Properties of Electrochemically and Chemically Prepared Polyaniline

Electrochemical potentiodynamic polarisation supported by SEM morphological examinations have been used to evaluate a range of chemically and electrochemically deposited polyanilines films for use in inhibiting corrosion, in particular 304L stainless steel. It was found that emeraldine salt coatings provided superior protection compared to their base counterparts. This was explained in terms of the more compact morphology and higher conductivity of the former, which allows the film to act as an electronic as well as a physical barrier. With respect to protection against pitting corrosion it appears that conductivity is the most important parameter, whereas for general uniform corrosion the morphological of the physical barrier seems to be dominant. It was also found that emeraldine salt coatings greatly reduced the rate at which active pits propagated, postulated to be due to the restricted ion mass transport through the film. Finally, it had been expected that the higher purity and compact morphology expected from electrochemical deposition would produce the best films. For general uniform corrosion this was indeed the case, however, for pitting corrosion the highly conductive chemically deposited films proved to be provide the best protection. This is an encouraging result, since chemical deposition is likely to prove the more economically viable method of application.