Conducting polymers represent a promising application prospect in the field of metal corrosion protection as a new polymer material since its reversible redox properties. Among the conducting polymers, polyaniline has become the focus in the anticorrosion coating field and has been widely applied in many fields like metal materials, chemistry industry, navigation and spaceflight because of its unique resistance to pitting corrosion and scratch and its inhibition to adhesion of marine organisms. In this paper, through the analysis of the deficient anticorrosion properties of the single polyaniline coatings, the research progress of modified polyaniline coatings in the field of metal corrosion protection in recent years are summarized, including a single ring substituted polyaniline coatings and N-substituted polyaniline coatings, modified polyaniline composite coatings and modified polyaniline composite materials/resin blending hybrid coatings. The anticorrosion properties of the modified polyaniline coatings and the unmodified polyaniline coatings are compared by various corrosion test methods, further proving that the electron-donating substituents (e.g., alkyl, alkoxy, amino, etc.) can improve the anticorrosion properties of polyaniline coatings, composite modification or blended with resin can also improve the anticorrosion properties of polyaniline and its derivatives. Meanwhile, the future study and development trend of polyaniline and its derivatives are prospected.

Contents
1 Introduction
2 Anticorrosion properties of substituted polyaniline derivatives
2.1 Ring substituted polyaniline derivatives
2.2 N-substituted polyaniline derivatives
3 Anticorrosion properties of polyaniline and its derivatives' composites
3.1 Polyaniline/inorganic composites
3.2 Polyaniline/polymer composites
3.3 Substituted polyaniline composites
3.4 Polyaniline and its derivatives composites/resin hybrid composites
4 Conclusion and outlook