Electrosynthesis of molybdate-doped P(ANI-co-PY) copolymer coating in ionic liquid for corrosion protection of 304 stainless steel

P(ANI-co-PY) and P(ANI-co-PY)-MoO₄²⁻ copolymer coatings with different molar ratios of aniline (ANI) and pyrrole (PY) monomers are electrosynthesized on the surface of a 304 stainless steel (304SS) in 1-butylsulfonic acid-3-methylimidazolium hydrogensulfate (BAMH) ionic liquid solution using cyclic voltammetry (CV) technique. P(ANI-co-PY) and P(ANI-co-PY)-MoO₄²⁻ copolymer coatings possess better surface compactness and thermostability than the pure PANI and PPY coatings. ¹H NMR studies and UV–vis tests confirm the successful copolymerization of the P(ANI-co-PY) polymer. The corrosion behaviors of the bare 304SS and PANI, PPY, P(ANI-co-PY), and P(ANI-co-PY)-MoO₄²⁻ coated 304SS are evaluated in a 0.1 M HCl solution via electrochemical methods. The charge transfer resistance (R_ct) is obtained by performing equivalent circuit fitting, and it is shown that the R_ct of P(50ANI-co-50PY)-MoO₄²⁻ copolymer coating is 10 times larger than that of the pure PANI and PPY coatings after being immersed in 0.1 M HCl for 240 h. A maximum corrosion protection efficiency of 99.3% is attained for P(50ANI-co-50PY)-MoO₄²⁻ copolymer coating, which indicates its superior corrosion protection ability. The excellent anti-corrosion performance can be attributed to (1) the physical barrier of the copolymer coatings, (2) anodic protection of the conductive polymers, and (3) the effective adsorption of BAMH onto the surface of 304SS.