Ziziphus joazeiro Stem Bark Extract as a Green Corrosion Inhibitor for Mild Steel in Acid Medium

The aqueous extract of Joazeiro stem bark (EJSB) and its high molecular weight fraction (HMWF) were examined as potential corrosion inhibitors mild steel in 1 mol L?1 hydrochloric acid media, using weight-loss measurements, potentiodynamic polarization curves an electrochemical impedance spectroscopy (EIS).Varying the concentration from 100 to 800 mg L?1, results show increase anticorrosive efficiency 85.4 89.8 93.0% for EJSB HMWF, respectively, data gravimetric essay, 84.5 94.5 89.9 94.7% data. composition crude was chemically characterized by liquid chromatography-high resolution mass spectrometry. Additionally, scanning electron microscopy (SEM) X-ray photoelectron (XPS) used, morphologically characterize surface. Considering that saponin molecules, main constituent juá, are responsible inhibitory action, quantum chemical calculations showed C67, C69 O144 atoms likely have important role process electron-donation metal, due higher values ƒk+ %HOMO observed on these atoms.