Carbon Steel Experiments

The material used throughout the experiments was a carbon steel with a chemical composition (in wt%) of 0.370 % C, 0.230 % Si, 0.680 % Mn, Ti, 0.054 %, 0.016 % S, 0.077 % Cr, 0.015 % Ni, 0.009 % Co, 0.160 % Cu and the remainder iron (Fe). The aggressive solution 1.0 M hydrochloric acid was prepared by dilution of an Analytical Grade 37% HCl with double distilled water. All experiments were carried out in molar hydrochloric acid solution in the absence and presence of various concentrations of Mahogany Extract.

The leaves of Mahogany were collected and dried in shade so as to enrich the active principles in them, by reducing their moisture content. 10.0 g of powdered dry leaves were refluxed in 500 mL of 1.0 M HCl for 4 h and kept overnight.

The carbon steel specimens of 2.0 cm x 1.0 cm x 0.5 cm sizes pre-treated weighed accurately using an analytical balance (precision ± 0.1 mg) before each immersion; the specimens were immersed in 100 ml of 1.0 M HCl with and without addition of different concentrations of LKS. After immersion period (6h), the steel specimens were withdrawn, carefully rinsed with double distilled water, ultrasonic cleaning in acetone, dried at room temperature and then weighted. Triplicate experiments were performed in each case and the mean value of the weight loss was

This potentiostat is connected to a cell with three electrode thermostats. A saturated calomel electrode (SCE) and platinum electrode were used as reference and auxiliary electrodes, respectively. The material used for constructing the working electrode was the same used for gravimetric measurements. The surface area exposed to the electrolyte is 0.32 cm2. Potentiodynamic polarization curves were plotted at a polarization scan rate of 1.0 mV/s. Before all experiments, the potential was stabilized at free potential during 30 min. The polarization curves are obtained from −800 mV to −200 mV/SCE at 293K. In order to investigate the effects of temperature and immersion time on the inhibitor performance, some test were carried out in a temperature range 293–313K. The inhibition efficiencies (%) for potentiodynamic polarisation measurements were calculated as