ABSTRACT
This chapter discusses the redox properties of Polyaniline (PANI) and its interaction with various metals and alloys, such as iron, steel, copper, aluminum alloy, and magnesium alloy. It explains the importance of the interface layer formed between the PANI coating and metal surface. PANI is regarded as one of the most promising environmentally friendly corrosion-inhibiting pigments. In the past decades, PANI has been widely investigated and demonstrated efficient corrosion-inhibiting ability for various metals, leading to commercial products and industrial applications since the mid-1990s. Numerous studies show that upon immersion of PANI-coated metals, the interaction between PANI and metal occurs, where PANI acts as catalyst experiencing a reversible reduction and oxidation reaction, while metal is oxidized to form an oxide layer. The most common PANI forms are emeraldine salt (ES) and emeraldine base (EB); both are redox-active polymers with equilibrium potentials, which are more positive to the standard potential of common metals, such as iron, aluminum, and magnesium.
