Corrosion protection of new composite polymer coating for carbon steel in sulfuric acid medium by electrochemical methods

In this paper, electropolymerization technique has been used for the obtained of new composite: polypyrrole – dioctyl sulfosuccinate sodium/poly N-ethylaniline (PPY-AOT/PNEA) coatings over carbon steel of type OLC 45 electrode for anticorrosion protection. The PPY-AOT/PNEA coatings were successfully synthesized onto OLC 45 electrode by galvanostatic deposition from aqueous solutions 0.1 M NEA, 0.1 M PY, 0.01 M AOT and 0.3 M H₂C₂O₄ solution at different current densities (5, 3 and 1 mA/cm²) in different molar ratio. The anionic surfactant (AOT) as a dopant ion used during electropolymerization can have a significant result on the anticorrosion protection of the composite film by hindering the penetration of aggressive ions. The polymeric composite coatings have been analyzed by cyclic voltammetry (CV), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) methods. The corrosion resistance of PPY-AOT/PNEA coated carbon steel has been examined by potentiodynamic polarization techniques and electrochemical impedance spectroscopy (EIS) methods in 0.5 M H₂SO₄ solutions. The data of the corrosion samples demonstrated that PPY-AOT/PNEA coatings assure a great anticorrosion protection of OLC 45 electrode in corrosive media. The corrosion rate of PPY-AOT/PNEA coated OLC 45 has been indicated to be ~9 times lower than of uncoated electrode. The corrosion protection effectiveness of the composite coating is more than 89%. The best efficiency is accomplished of PPY-AOT/PNEA obtained by electrodeposition at 5 mA/cm² current densities applied in molar ratio 5:1.