Synthesis of natural glucomannan derivative as a highly-efficient green inhibitor for mild steel in the simulated seawater

Herein, we report a rational design and synthesis of a highly-efficient and eco-friendly glucomannan derivative (GA-2) by the introduction of the thiazole and Schiff base groups into glucomannan (GA). After confirmation of GA-2 by the spectroscopic methods, it was introduced as corrosion inhibitor with excellent anti-corrosion action for mild steel (MS) in the simulated seawater. As-obtained results reveal that GA-2 has a significantly enhanced anticorrosion performance, and its inhibitive efficiency reaches 98.8% at the 0.5 mmol L−1 inhibitor concentration, much higher than that of GA (69.8%) and the intermediate derivative GA-1 (81.2%). The significantly enhanced protection performance could be attributed to the rich S heteroatoms, aromatic rings, and Schiff base groups in the GA-2, which strongly promotes the chemisorption as well as physisorption between GAD and MS. X-ray photoelectron spectroscopy (XPS) results, show that the appearance of N-Fe and S-Fe bonds confirms the strongly anchoring interaction between GA and MS. Furthermore, according to the quantum chemical calculations, the results from the lowe energy gap and radical distribution function (RDF) analyses further confirm the strong chemisorption of GA-2 at the surface of steel, which illustrates the excellent inhibition performance at the molecule and atom level.