Corrosion resistive conducting polymeric nanocomposite-based coatings on steel: a mechanistic insight

Abstract Conducting polymers and polymer-based nanocomposites has occupied significant importance in the scientific field as well as engineering research and applications. Among all different applications, conducting polymers as a corrosion resistive coating on steel have developed a lot of research interest and success for the last four decades. This paper provides an extensive review on the corrosion resistive conducting organic polymer coating systems over steel substrates. It mainly discusses different mechanisms of corrosion provided by different conducting polymer coatings over steel. The corrosion resistance mechanisms of coatings based on polyaniline (PANI) and polypyrrole (PPy) and their nanocomposites, which are considered very promising conducting polymers in different fields, are reviewed here. PANI provides corrosion resistance via different mechanisms. PANI in oxidised form can offer effective anodic corrosion resistance to steel surface due to its higher oxidising ability than in reduced form. It can provide a good extent of barrier protection to steel as well. PPy also can provide both the barrier and anodic protection. The mechanism of intelligent release of doped corrosion inhibitive anions from the conducting polymer coating and its contribution to corrosion protection mechanism of steel is also focused in this article. The limitations of conducting polymer coating are briefly discussed.