Corrosion resistant hydrophobic coating using modified conducting polyaniline

Almost all metals and their alloys are vulnerable to corrosion. To avoid structural damage and to avoid loss of its functionality, the most common protection method used is the application of a coating. In the present work, hydrophobic coatings using modified conducting polyaniline (PAni) were prepared and their corrosion-resistant properties were investigated. Modified PAni was prepared via two different techniques, conventional and rapid mixing method, in the presence of phenyl phosphonic acid (PPA) as dopant. The different PAni-PPA powders thus prepared were dispersed in an epoxy resin and coated on mild steel samples by drawing method. Tremendous improvement in hydrophobicity of the PAni-PPA (rapid)/epoxy was observed as compared to epoxy resin containing PAni-PPA (conventional method). The anticorrosion properties of these coatings on mild steel in 3 wt% NaCl were investigated using different electrochemical methods. Initial redox reactions and changes in conductivity of coating were reflected in the variations of open circuit potential (OCP). Both the coatings displayed stable high OCP, maintained their oxidative state, and provided corrosion protection for mild steel for more than 30 days. PAni-PPA (rapid)/epoxy gave better corrosion protection and showed higher ennoblement which may be due to the small particle size of PAni-PPA (rapid) leading to homogeneous mixing and better dispersion in the epoxy resin. Moreover, this coating is more hydrophobic in nature which is added advantage in case of corrosion-resistant coatings. The present investigation deals with preparation of highly (near super) hydrophobic coating containing conducting polymers for anticorrosion applications.