Corrosion protection efficiency of the electrochemically synthesized polypyrrole-azo dye composite coating on stainless steel

The polypyrrole-azo dye (Lanaset-Red-2B) composite coatings were electrochemically deposited on stainless steel 430 by means of repetitive cyclic voltammetry. The composite coatings were synthesized by addition of the dye in 10−6–10−3 M range to 0.1 M oxalic acid solution containing 0.1 M pyrrole monomer. All polypyrrole/Lanaset-Red-2B composite coatings are more protective with respect to the pristine polypyrrole in NaCl (3.5%) medium. The best protective coating synthesized in the presence of 10−5 M dye using optimized potential range, scan-rate and cycle number were characterized by infrared-reflection-absorption-spectroscopy, scanning-electron-microscopy and energy-dispersive-spectroscopy analyses. The electrochemical characterizations were performed by using potentiodynamic polarization and electrochemical-impedance-spectroscopy techniques. The steel coated with the polypyrrole/Lanaset-Red-2B composite is more resistant in 0.1 M H2SO4 solution comparing to NaCl (3.5%) during long-term immersion until 432 h. The corrosion protection efficiency of the coating is higher than that of its initial value at the end of 432 h immersion in both media due to controlled release of the Lanaset-Red-2B deposited as inhibitor in the polypyrrole structure.