Self-doped poly(aniline-co-metanilic acid) copolymer coatings for enhancing the corrosion resistance of 304 stainless steel

Self-doped conducting poly(aniline-co-metanilic acid) (SPANI) copolymer coatings are electropolymerized for corrosion protection of 304 stainless steel (304SS) in a 0.3 M HCl solution. The synthesized SPANI coating is more compact and uniform, which exhibits improved barrier resistance to aggressive ions. The potentiodynamic polarization curve and electrochemical impedance spectroscopy results show that the SPANI copolymer coatings significantly suppress the corrosion current density, increase the charge transfer resistance, and effectively inhibit corrosion of the 304SS substrate. In addition, the SPANI copolymer coating exhibits a nondestructive topography after 120 h of immersion in a corrosive environment, which further confirms its superior protection performance. Owing to their enhanced physical barrier effect (compact coating surface with low porosity) and superior anodic protection, SPANI copolymer coatings are more corrosion resistant. Furthermore, the outcomes of the quantum chemical calculation and molecular dynamic simulation indicate that the SPANI copolymer chains are more stabilized and display favorable compatibility with the Fe (1 1 0) surface via electrostatic force. The better surface coverage and higher adsorption activity ensure an excellent chemical-anchor effect on the Fe (1 1 0) plane and thus achieve higher corrosion inhibition efficiency of the SPANI copolymer coatings.