Combining experimental and theoretical researches to insight into the anti-corrosion property of Morinda citrifolia Linn leaves extracts

Abstract With the establishment of the concept of a community with a shared future for mankind, more and more eco-friendly corrosion inhibitors have attracted the attention of corrosion scientists. In this study, Morinda citrifolia Linn leaves extracts (MCLLE) were obtained using pure water extraction method. The extraction solvent, extraction method and the obtained product MCLLE will not cause damage to the ecological environment. The surface topography test vividly further proves that MCLLE can exhibit good anti-corrosion nature. Quantum chemistry calculation data show that (S)-2-amino-3(1H-imidazol-4-yl)propanoic acid (APA), 2-(6-Amino-purin-9-yl)-5-hydroxymethyl-tetrahydro-furan −3,4-diol (AHT), (S)-2-amino-4-(methylthio)butanoic acid (ABA), (S)-2-amino-3-(1H-indol-3-yl)propanoic acid (AIA), (S)-2-amino-5-guanidinopentanoic acid (AGA), (S)-2-amino-3-phenylpropanoic acid (APA) of MCLLE can exhibit brilliant corrosion inhibition property. In addition, molecular dynamics simulations show that APA, AHT, ABA, AIA, AGA, and APA have large binding energy on the copper surface, indicating that the obstacle film formed onto the copper surface is comparatively dense. Electrochemical experimental data indicate that the MCLLE anti-corrosion efficiency of 800 ppm can reach more than 95% for copper in 0.5 M H2SO4 environment. MCLLE can suppress the cathodic reaction and anodic reaction of the copper electrode. The adsorption of MCLLE onto the copper surface accords with Langmuir adsorption.