Investigating corrosion inhibition of aluminum alloy by green inhibitor propolis in 3.5% NaCl solution

Abstract

Propolis, which has an antioxidant characteristic, is proposed as a green corrosion inhibitor for aluminum alloy (AA). The inhibition effect of propolis was studied on AA7075. Propolis concentration was varied for 0, 200, 400, 800, and 1200 mg/L, added to 3.5 wt.% NaCl solution. Corrosion behavior was investigated using electrochemical and mass loss tests. The potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) analysis revealed the significant corrosion inhibition effect obtained for propolis concentrations of 400 and 800 mg/L. From the electrochemical tests, propolis was considered a cathodic inhibitor as it caused a depression in the cathodic current densities approximately ten times. The gain of remarkable film resistance suggested that the inhibition mechanism was due to thickening of the surface film through adsorption of the propolis molecules. The adsorption behavior followed the Langmuir adsorption isotherm. The optimum inhibition efficiency measured from PDP, EIS, and mass loss data was obtained at 400 mg/L propolis. Propolis shows promise as corrosion inhibitor for Al alloys.