Derivatives Of L-cysteine ​​and Its Inhibition Properties With The Qsar Study

Corrosion inhibitors hold the important status in the metal protection project as an economical and effective anticorrosion method. Especially recent years, novel effective and environment-friendly corrosion inhibitors are more and more popular in the view of environment protection and sustainable development strategy. Amino acid compands were much more widely used in corrosion inhibitors research because of their extensive sources, nontoxicity and easy degradation.Three kinds of L-cysteine derivatives including ten novel compounds were involved in this paper, which were non-toxicity and environmentally friendly. The inhibiting performance of eight compands of all and L-cysteine were evaluated by weight loss, electrochemical test, quantum chemical calculations and molecular dynamics modeling. This paper discussed the corrosion inhibiting mechanism of these derivatives and the relationship between the molecular structure and their inhibiting efficiency. Main achievements were listed as follows:By referring to literatures, we established and improved the synthesis methods of L-cysteine derivatives,which enhanced products yield compared to literatures methods. According to these methods, we sythesised S-alkyl-L-cysteine, N-acetyl-L-cysteine, N-acetyl-S-alkyl-L-cysteine and L-cysteine ethyl ester hydrochloride. The target products were confirmed by FT-IR and 1H-NMR.Weight loss test and electrochemical measurement results indicated that L-cysteine and its derivatives were effective corrosion inhibitors for carbon steel in HC1 solutions. Compared to L-cysteine, the inhibition efficiency of its derivatives increased in various degrees, wherein the inhibition efficiency of compound S-benzyl-L-cysteine arrived at 82% at 10-2mol/L. The inhibition mechanism was that L-cysteine and its derivatives moleculars absorbed on carbon steel surface forming a layer of dense protective film and inhibited its electrochemical cathode and anode processes to reduce the corrosion current density. As the concentration of the inhibitors increased, the inhibition efficiency enhanced. It was preliminarily concluded that L-cysteine and its derivaives were mixed type inhibitors.Quantum chemical calculation acquired the molecular optimized geometries, and was theoretically provided the absorption sites of these L-cysteine and its derivatives molecules. Based on the research of the quantitative structure-activity relationship(QSAR) of these inhibitors, the possible mode of inhibition equations were presumed. It is useful to provide some valuable information to synthetic new corrosion inhibitors.We constructed a model of inhibitor-water-metal interface using Materials Studio 4.0 Through molecular dynamics modeling, we investigated absorbtion and film-forming behaviors of L-cysteine and its derivatives on Fe(110) surface in aqueous environments。...