A Thermodynamic Study of Inhibition of Copper Alloy Corrosion in Nitric Acid Using Laurel Leaf Extract

The corrosion inhibition efficiency of copper alloy in HNO₃ solution at different concentrations (0.5, 1, 1.5, and 2 mol/L) was studied by adding bay leaf extract at different concentrations (1000, 2000, 3000, and 4000 ppm). The effect of concentration on the corrosion rate was studied in both the absence and presence of the inhibitor, in addition to choosing the acid concentration (1 mol/L) and varying inhibitor concentrations. The research also included studying the effect of temperature on the corrosion rate in both the absence and presence of the inhibitor. The weight loss method was used to calculate the corrosion rate. A negative heat of adsorption indicates that the reaction is exothermic. The adsorption free energy of the bay leaf extract ranged from 4.6 to 6.1 kJ/mol, and the results indicated that Langmuir adsorption was best. The results of this study showed that the inhibitor reduces corrosion in acidic media and that the inhibition efficiency increases with increasing inhibitor concentration and decreases with increasing temperature. The inhibition rate of the extract reached (92.31%) at an acid concentration of 0.5 mol/L, an inhibitor concentration of 4000 ppm, and a temperature of 298 K. This study showed that the inhibitor has a high corrosion resistance. The results also showed that the bay extract exhibits inhibitory activity, likely due to its high viscosity and high levels of phenolic compounds and flavonoids, as indicated by the HPLC test.