Banana leaves water extracts as inhibitor for X70 steel corrosion in HCl medium

Abstract

In this work, we used experimental and theoretical calculation methods to investigate the corrosion inhibition nature of banana leaves water extract (BLWE) for X70 steel at 1 mol/L hydrochloric acid environment. The data of electrochemical tests manifest that the hydrochloric acid medium will accelerate the corrosion of X70 steel with increasing temperature. The charge transfer resistance dropped sharply from 55 Ω cm2 at 298 K to 18.4 Ω cm2 at 313 K. After adding BLWE in hydrochloric acid solution, the anti-corrosion efficiency of banana leaves extract for X70 steel can be maintained at about 90%. BLWE can simultaneously inhibit the anodic and cathodic reactions of X70 steel in hydrochloric acid solution, so it is mixed-type inhibitor. Surface morphology analysis strongly shows that BLWE can effectually restrain the corrosion of X70 steel. BLWE adsorption at the X70 steel surface is accord with Langmuir single-deck adsorption. Quantum chemical (QC) calculation and molecular dynamics simulations (MDS) have shown that (S)-2-amino-3-(4-hydroxyphenyl)propanoic acid (AHP), 3-(2-aminoethyl)-1H-indol-5-ol (ATI), and 3,4-Dihydroxycinnamic Acid (DDA) in BLWE can show excellent anti-corrosion character. QC calculation results show that AHP, ATI and DDA have small dipole moment values. The small dipole moment value is favorable the accumulation of inhibitor molecule on the X70 steel surface, thereby forming a denser barrier film. MDS results show that AHP, ATI and DDA can be adsorbed on the Fe (110) surface in parallel to obtain the maximum coverage.