Dramatic improvement in corrosion inhibition effect of carboxymethyl cellulose by modified with levodopa: Experimental study and first-principles calculations

Cellulose , as a kind of renewable natural polymer , has great potential as green corrosion inhibitor . However, the low inhibition effect is the obstacle to its practical application. Herein we developed a high efficiency green cellulose derivative corrosion inhibitor , levodopa-carboxymethyl cellulose (LDCMC), by modifying carboxymethyl cellulose (CMC) with levodopa (LD) through a simple amidation reaction. The inhibition effect of CMC for mild steel in HCl medium is dramatically improved with an increase in inhibition efficiency from 56.98% of CMC to 97.27% of LDCMC. The intrinsic nature of the dramatically improved inhibition effect is in-depth unraveled by first-principles calculations based on density functional theory (DFT). CMC and LDCMC can adsorb on the mild steel surface through -OH, -COOH and LD fragment by forming the covalent bonds with steel surface. Benefiting from the additional strong adsorption of the benzene ring in LD fragment, the introduction of LD can significantly enhance the adsorption capacity of LDCMC, which is the intrinsic nature of the dramatical improvement in the inhibition effect of LDCMC.