Effect of ortho-phosphoric acid doping concentration on electrochemical properties of polyaniline coated low carbon steel

Abstract

Conducting polyaniline-based paint formulation is prepared and coated on the low carbon steel samples. Characterization of conducting polyaniline showed the characteristic peak at 327 nm and a weak broad peak at 608 nm under UV–Vis’s spectrometry. The effect of doping level on electrochemical performance of conducting polyaniline painted low carbon steel was studied using ortho-phosphoric acid as a dopant. All polyaniline-based painted steel samples exhibited a shift in corrosion potential positively and a reduction in corrosion rate. However, the corrosion rate of 0.3 M ortho- phosphoric doped conducting polyaniline coated low carbon steel sample is found to be 0.01 mpy, significantly lower than that of painted and unpainted samples. Higher impedance modulus, coating resistance, and lower coating capacitance confirm the corrosion resistance of 0.3 M ortho-phosphoric doped conducting polyaniline coated low carbon steel sample in a neutral medium. It reveals that doping plays an essential role in the electrochemical performance of the painted steel samples and protects the steel by a barrier and anodic protection.