Electrochemical synthesis and corrosion behaviour of polyaniline on stainless steel in sodium hydroxide solutions

Polyaniline (PAni) has been electropolymerized on stainless steel surface (SS321) by cyclic voltammetry technique from aqueous solutions of 0.1 M aniline in 0.1 M acetic acid, oxalic acid, hydrochloric acid and sulfuric acid solutions. The anticorrosion performance of PAni coating electropolymerized in sulfuric acid solution was investigated in 0.1 M NaOH solutions using potentiodynamic polarization curves technique. The influence of scan rate, cycle number, formation temperature, as well as supporting electrolytes on the anticorrosion performance of PAni film were investigated. The polymer film formation in presence of acetic or hydrochloric acid is attributed to the oxidative mechanism in contrary to the reductive mechanism proposed in presence of oxalic or sulfuric acid. The best protection efficiency of PAni coatings was obtained when prepared in acetic acid solution. The morphology of PAni coatings before and after polarizing SS 321 in 0.1 M NaOH solutions was examined using scanning electron microscope (SEM) and Energy dispersive x-ray (EDX). It was noted that PAni coating morphology was highly influenced by the nature of acid anion present.