Effect of molecular weight on inhibition performance of modified polyethyleneimine as polymer corrosion inhibitor for carbon steel in neutral medium

Compared with small organic molecular, polymer corrosion inhibitors exhibit better anti-corrosion performance in neutral medium because of multiple adsorption sites and temperature toleration, which are becoming the focus of scholars in the field of water treatment. However, the effect of molecular weight of polymer inhibitors is rarely studied, which has a significant impact on its performance. Polyethyleneimine (PEI) containing polar groups and numerous N atoms is a kind of water-soluble polymer which is prone to being modified, and three kinds of modified polyethyleneimine (PEPA) inhibitors are synthesized by PEI with different molecular weights (600, 1800, 10,000) in this work. The anti-corrosion performance of PEPA for Q235 carbon steel in neutral medium was evaluated by electrochemical measurements (Tafel polarization plots and electrochemical impendence spectroscopy [EIS]), weight-loss tests, and surface morphology analysis. Results of weight loss method and other measurements confirm that PEPA is an excellent polymer inhibitor, and the inhibition performance of PEPA synthesized by PEI with molecular weight of 1800 is the best with an inhibition efficiency of 94.6% at a dosage of 200 mg/L at 298 K in neutral medium.