Anticorrosive properties of Eucalyptus (Nilgiris) leaves extract on 2S grade aluminium in acid solutions

The study is on the application of Eucalyptus leaves extract (ELE) as anticorrosive properties for aluminium alloy in 0.5 M HCl by using potentiodynamic polarization (PDP), gravimetric weight loss, and Electrochemical impedance spectroscopic (EIS) methods. The corrosion inhibition characteristics of ELE on aluminium in HCl solution have been examined. This investigation showed the finest inhibition efficiencies of 95.0%, 92.0% and 89.3% that were obtained from weight loss, PDP and EIS at concentration of 0.5% ELE at 303 K respectively. As per Langmuir adsorption isotherm models, an extract of Eucalyptus leaves was adsorbed on the metal surface. The effect of the temperature on the corrosion behaviour with adding of the best concentration of ELE was studied in the temperature range 313–333 K. It was found that inhibition efficiency is independent of temperature. The negative Gibb's free energy and activation parameters of the ELE were recorded and the results indicated that the adsorption rates were spontaneous. The results obtained from PDP and EIS shows that the corrosion inhibition procedure is charge transfer controlled, and the ELE works as a mixed-type inhibitor. The findings of SEM (Scanning electron microscopy) and AFM (Atomic force microscopy) studies support the adsorption inhibition mechanism. The results of all the experiments conduct are consistent. The functional groups of the ELE were identified using Fourier transform infrared (FTIR) spectroscopy.