Experimental and theoretical investigations on the corrosion inhibition performance of acrylamide-allyltriphenylphosphonium bromide copolymer for mild steel in 1 M HCl aqueous solution

• A novel modified polyacrylamide corrosion inhibitor (PAA) was synthesized. • 10 mg/L PAA exhibits 85.56 % inhibition efficiency on mild steel in HCl solution. • The inhibition performance of 10 mg/L PAA is greater than that of 500 mg/L PAM. • The benzene rings greatly enhance the compactness of the protective adsorption film. Polyacrylamide (PAM) is widely considered as an ideal candidate for metal corrosion inhibitors due to its cost-effectiveness. Numerous studies improved its corrosion inhibition performance through functional group modification. This study synthesized a novel high-performance modified polyacrylamide corrosion inhibitor (P(AM-co-ATPB), abbreviated as “PAA”) by copolymerizing acrylamide (AM) and allyltriphenylphosphonium bromide (ATPB) monomers. The corrosion inhibition performance of PAM and PAA was evaluated through weight loss tests, surface characterization and electrochemical experiments. PAA can inhibit the mild steel (MS) corrosion in 1 M HCl solution more effectively at the ultralow concentration of 10 mg/L ( η M =85.56 %) than polyacrylamide (PAM) at 500 mg/L ( η M =83.17 %). Then the inhibition mechanism was further investigated using Langmuir adsorption isotherm fitting, quantum chemical (QC) calculations and molecular dynamics (MD) simulations. The unique benzene ring, P and Br atom in PAA enhanced both physical and chemical interactions between the corrosion inhibitor molecules and MS surface Fe atoms. And the π-π stacking among PAA molecules further strengthened the adsorption layer compactness, which should be responsible for its superior corrosion inhibition performance than PAM. This study proved that the additional monomer ATPB markedly improved PAM-based corrosion inhibition efficiency, providing a novel perspective for the molecular structure design of PAM-based corrosion inhibitors.