The electrochemical study of the garlic extract as a corrosion inhibitor for brass in the nitric acid solution

The aim of this study was to investigate the corrosion behavior of the brass alloy in the 1 M HNO3 solution with the different concentrations of the green inhibitor (Garlic extract). In the first step, the fourier transform infrared spectroscopy was used to identify the chemical composition of the inhibitor. The inhibition effect of the garlic extract on the corrosion behavior of the brass alloy was investigated by the polarization and electrochemical impedance spectroscopy test. The results of the polarization test showed that the garlic extract in the acidic environment acted as a mixed-type inhibitor, and with increasing the inhibitor concentration, the inhibitor efficiency increased from 60 % to 93.74 %. In addition, the results of the electrochemical impedance test revealed that by increasing the inhibitor concentration, the capacitance of the capacitor of electric double layer decreased, while the solution resistance increased. In follow, the effect of temperature on the corrosion behavior of the brass alloy with the presence of the garlic extract in the acidic solution was investigated using the electrochemical techniques as well. The results showed that by increasing the temperature, the inhibitor efficiency decreased from 93.74 % to 83.47 % at 3 g/L of inhibitor. Furthermore, the surface of the sample after dipping in the nitric acid solution containing garlic extract was examined using a scanning electron microscopy and an atomic force microscopy. The adsorption of the inhibitor molecules on the surface of the brass alloy at all temperatures was studied using the Langmuir adsorption isotherm and then both chemical and physical mechanisms were observed due to the adsorption of the garlic extract on the surface of the brass alloy in the 1 M HNO3 solution.