Electrochemical and surface characterizations of morus alba pendula leaves extract (MAPLE) as a green corrosion inhibitor for steel in 1 M HCl

Recently the researchers' attention has been directed toward using environmentally friendly corrosion inhibitors extracted from plant leaves for corrosion protection of steel structures against acidic environments. The objective of this study is using morus alba pendula leaves extract (MAPLE) as a new green corrosion inhibitor for carbon steel in 1 M HCl solution at different concentrations(0.1-0.4 g/L) and temperatures (25-60 degrees C). In addition, the effect of addition of potassium iodide (KI) to the MAPLE was studied. Electrochemical investigations were performed by electrochemical impedance spectroscopy (EIS) and polarization test. Also, surface characterizations were done on the steel panels exposed to 1 M HCl solutions containing MAPLE by atomic force microscope (AFM) and Fourier transform infrared spectroscopy (FT-IR). The inhibitor adsorption/desorption behaviors in the 1 M solution was studied by UV-visible analysis. Results obtained from electrochemical measurements revealed that a high inhibition efficiency value of 93% was achieved in the presence of 0.4 MAPLE at room temperature (25 degrees C). A synergistic effect was observed between KI and MAPLE with optimum concentration of 0.4g/L MAPLE+ 10 mM KI. Adsorption of extract on the steel surface in the presence of KI resulted in an inhibition efficiency of 96%. The presence of flavonoids such as morusin, kuwanonC and kuwanonG, phenolic acids and pyrrole alkaloids in the MAPLE is responsible for its high inhibition efficiency in 1 M HCl solution on the steel surface. It was found that MAPLE acted as a mixed type corrosion inhibitor and the inhibition efficiency was increased by increasing the inhibitor concentration obeying a Langmuir adsorption isotherm. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.