Multi-scale theoretical calculation-based screening and synthesis of a green corrosion inhibitor for Q235 steel in 1 M HCl

• Rapid screening by combinations of QM, MD and MC. • Intramolecular synergy of NA and Met is stronger than intermolecular coordination. • SEM,AMF and CCI show the steel surface inhibited by MPA is nearly uncorroded and very smooth. • Revealing the reasons for differences in inhibition efficiency at the atomic level. Corrosion inhibitors are toward the development of environmentally friendly direction. Nicotinic acid (NA) and amino acids could be used as green corrosion inhibitors to protect metal materials. However, its inhibition performance is not stable, so the use of nicotinic acid modified amino acids to improve its corrosion inhibition performance. In this work, firstly, the performance of the nicotinoyl-methionine (MPA) and nicotinoyl-cysteine (SPA) was compared by theoretical calculation. Then, the corrosion inhibition performance of MPA and the raw materials, NA, methionine (Met), and their combination (NM) were investigated by weight loss, electrochemical tests, surface characterization and theoretical calculation. Through the combination of quantum chemical calculations, molecular dynamics and Monte Carlo simulations, the green and highly efficient inhibitor was quickly screened out, MPA exhibited superior corrosion inhibition behavior. Meanwhile, the results of weight loss and electrochemical tests showed that MPA exhibited excellent corrosion inhibition performance (96.31 %) compared with NA (56.45 %), Met (68.42 %), and NM (88.45 %). Combined with surface characterization and theoretical calculations, the enhanced corrosion inhibition performance of MPA was attributed to the synthesis of amide groups to tightly connect NA and Met as well as to have more active adsorption sites with stronger adsorption capacity.