Inhibition Effect of Orange Peel Extract on Aluminum in Hydrochloric Acid Solution

Orange peel extract(OPE) was prepared by reflux extraction method with ethanol aqueous solution, and its functional groups were characterized by infrared spectrum(FTIR). The inhibition effect of OPE on aluminum in 1.0 mol/L HCl solution was studied in detail for the first time by weight-loss, electrochemical technique, and surface analysis methods. The results showed that inhibitive performance increased continuously with the increase of OPE concentration, but turned to be lower with at higher temperature. When the OPE concentration is in the range of 300 mg/L–900 mg/L at 20 ℃, its inhibitive action is in stable state, and the maximum inhibition efficiency is as high as 98%. The adsorption of OPE was in accordance with Langmuir adsorption isotherm, and its adsorption mode was the mixed adsorption while mainly the physisorption. Polarization curves indicated that the presence of OPE significantly retarded the cathodic reaction of aluminum electrode in HCl solution, while slightly inhibited the anodic reaction, and then leaded to lower corrosion current. Electrochemical impedance spectroscopy(EIS) contained 2 time constants, and Nyquist appears a capacitive loop at high frequencies followed by an inductive one at low frequency values, and the charge transfer resistance increases with the addition of OPE. Scanning electron microscope(SEM) and atomic force microscope(AFM) revealed the corrosion degree and surface roughness of aluminium surface was sharply dropped to more extent after adding OPE to the media.