The effect of electrolytes on the coating of polyaniline on mild steel by electrochemical methods and its corrosion behavior.

• PANI coating on mildsteel is reported in sodium-potassium tartrate (Na-K Tartrate) and benzoic acid in alcohol-water (BAW) system. • A new composition of the BAW system is optimized and used for aniline polymerization for the first time. • The PANI coating formed in Na-K Tartrate and BAW electrolyte is a pore-free, compact, and fine-grained nanostructured. • The new electrolyte systems do not show an anodic peak during the cathodic scan indicates superior cyclic stability. Polyaniline (PANI) is extensively researched as a corrosion protection coating for mild steel (MS) against acidic and neutral media. Corrosion inhibition performance of PANI coating on MS depends on the electrolytic solution employed for polymerization. In this study, the electropolymerization of aniline onto MS using sodium potassium tartrate (Na-K tartrate) and benzoic acid in the alcohol-water (BAW) medium is reported. The composition of BAW system was optimized and used for electropolymerization of aniline for the first time. The results showed the formation of a passive yet electro-conductive layer before the polymerization initiated. A compact layer with a fine structured PANI coating in both media was obtained. Cyclic voltammetry (CV) produced a stable PANI coating without showing anodic current in the cathodic scan. The concentration of aniline and electrolytes were optimized for better coating conditions. The prepared PANI coating was characterized by Fourier-transform infrared (FTIR) spectroscopy, Ultraviolet-visible (UV–vis) spectroscopy, Scanning electron microscope (SEM) in combination with energy dispersion spectrometer (EDX) and X-ray diffractometer (XRD). The results of PANI coating in Na-K tartrate and BAW medium are compared with a standard PANI coating prepared in oxalic acid medium. The inhibition efficiencies of PANI coating obtained in Na-K tartrate and BAW were estimated to be 82.5 % and 99.99 %, respectively in 0.1 M NaCl solution. [ABSTRACT FROM AUTHOR]