Corrosion Inhibition Effect of Neem Leaf Oil Distillates on Low Carbon Steel in Dilute HСl and NH4Cl Acid Media

Neem leaf oil distillates (NLD) was evaluated for its corrosion inhibition properties on low carbon steel in 0.5 M HCl, 1 M HCl, 3.74 M NH4Cl and 5.61 M NH4Cl solutions. Weight loss analysis shows NLD performed effectively at all concentrations studied in HCl media with optimal inhibition efficiencies of 97.54% and 97.56% at 5% NLD concentrations. NLD performed poorly at 1-4% NLD concentration in 3.74 M and 5.61 M NH4Cl solutions with protection performance values below 50%. At 5% NLD concentration the protection performance values increased sharply to 78.53% and 79.0% at 312 h of exposure. Standard deviation values for NLD protection performance output in 0.5 M HCl solution were significantly high indicating highly unstable inhibition behavior and thermodynamic tendency to corrode with respect to exposure time. At 5% NLD concentration the standard deviation value decreased significantly. In 1 M HCl, 3.74 M NH4Cl and 5.61 M NH4Cl solutions the standard deviation values were relatively low due to improved stability of protonated NLD molecules in interaction with the steel surface. Experimental data showed 92.44%, 100%, 30.77% and 20% of NLD protection performance data from 0.5 M HCl, 1 M HCl, 3.74 M NH4Cl and 5.61 M NH4Cl solutions are above 70% inhibition value with margin of error of +7.99, +0, +11.22 and +9.72. Statistical data from analysis of variance showed exposure time dominates the performance output of NLD distillate on low carbon steel from 0.5 M HCl and 1 M HCl at values of 81.76% and 82.03% compared to the effect of NLD concentration which were negligible. In NH4Cl solution, NLD concentration dominates the protection performance output of NLD on the carbon steel compared to exposure time with values of 96.42% and 96.95%.