Comprehensive investigation of modified polyethyleneimine as an efficient polymeric corrosion inhibitor in neutral medium: Synthesis, experimental and theoretical assessments

Polymeric corrosion inhibitors have superiorities compared with small organic molecules, such as containing multiple adsorption sites and being easier to form multilayer films on metal surface. Polyethyleneimine (PEI) with polar group and hydrophobic group is a kind of water-soluble polymer which is prone to be modified and used as corrosion inhibitor in neutral medium, and polyethyleneimine phosphorous acid (PEPA) was synthesized by facile method. The anti-corrosion performance of PEPA for mild steel in neutral medium was evaluated by weight-loss tests, electrochemical measurements concerning Tafel polarization plots and electrochemical impendence spectroscopy (EIS), surface morphology analysis and theoretical calculation. Results of gravimetric and electrochemical tests indicate that PEPA as polymeric corrosion inhibitor present excellent inhibition efficiency in neutral corrosive medium, The adsorption model of PEPA conformed to Langmuir adsorption isotherm involving both physisorption and chemisorption, and morphology observations manifest the extent of corrosion of mild steel with the addition of PEPA is obviously reduced. Theoretical calculations including quantum chemical calculation and molecular dynamics simulation (MD) further reveal the adsorption mechanism of inhibitor PEAP at molecular or atomic level.