Investigation of protective effect of poly(N-ethylaniline) coatings on iron in various corrosive solutions

Poly(N-ethylaniline) (PNEA) coatings were deposited by potentiodynamic synthesis technique on the Fe and Pt-disc electrode. Coating conducted using oxalic acid aqueous solution containing N-ethylaniline monomer. PNEA polymer growth was found much less on Pt surface than that on Fe surface. The PNEA coatings were characterized both electrochemically and spectroscopically. Corrosion protection of the PNEA coating was investigated in 0.5 M H2SO4, 0.1 M HCl and 0.5 M NaCl solutions by linear anodic potentiodynamic polarization, Tafel test and electrochemical impedance spectroscopy techniques. For comparison, PAni was also deposited by potentiodynamic synthesis technique on the Fe surface. The presence of the PNEA and PAni coatings on Fe electrode restricts dissolution potential interval according to linear anodic potentiodynamic polarization curves obtained in 0.5 M H2SO4. The maximum dissolution current density values for the PNEA and PAni coated Fe electrode were found 10.7 mA cm− 2 and 11.6 mA cm− 2 respectively. These current density values were significantly low as compared to the bare electrode (41.8 mA cm− 2). Tafel test results showed that PNEA coating exhibited significant corrosion protection properties in NaCl medium than that of HCl medium. Long term impedance measurements of PNEA coated and uncoated electrodes in NaCl and HCl solutions shown that corrosion protection properties of the PNEA coating exhibited significantly high in NaCl medium (Rct value of 135.02 Ω cm2 after 196 h) as compared to the HCl medium (Rct value of 20.30 Ω cm2 after 48 h). The corrosion results obtained with three different independent electrochemical methods in three different corrosive media are in full agreement with each other.