Abstract
This study investigates the performance of myrrh plant extract as a corrosion inhibitor for a copper–zinc alloy in 3.5 wt% NaCl solution polluted by 16 ppm sulfide. The inhibition behavior was determined through a gravimetric method, electrochemical measurements, AFM, UV spectroscopy and FTIR. The results demonstrated that the efficiency of inhibition increases with increasing concentration of the myrrh extract and decreases with temperature. The corrosion rate of a copper –zinc alloy was decreased in the presence of myrrh extract. The corrosion inhibition efficiency was found to increase with myrrh concentration to a value of 67% at 300 ppm and 25 °C. The thermodynamic activation parameters that govern the process were deduced from the temperature dependence. Potentiodynamic polarization curves indicated that the myrrh extract behaves as a mixed-type inhibitor. This extract was adsorbed on a copper alloy surface following the Langmuir adsorption isotherm and a kinetic model adsorption isotherm. The adsorption free energy of the myrrh extract on the copper zinc alloy reveals a physical adsorption of myrrh on the alloy surface. The results of atomic force microscopy, and Fourier transform infrared and UV-visible spectrophotometric methods support the electrochemical measurements and gravimetric method.