Study on the Effects of Vitex negundo and Catharanthus roseus Leaves Extract as a Green Inhibitor for Corrosion Control of Mild Steel in Bioethanol and its Blend

Abstract

The study of the effect of Nepal origin Vitex negundo and Catharanthus roseus plant extracts on the corrosion behavior of mild steel in pure bioethanol (E100) and its 15 % blend (E15) with 85 % commercially available Euro-4 grade petrol (E0) was carried out using corrosion tests, corrosion inhibition efficiency and mechanism at 25 ± 2 °C in airtight condition. Fourier transform infrared (FTIR) spectra were used to characterize the used E100, E15 blend, and commercially available Euro-4 grade petrol (E0). Among E100, E15, and E0 fuels, the E100 has the highest corrosion susceptibility to the mild steel; mostly due to the water-absorbing ability of E100 and E15. However, the corrosion resistance property of the mild steel was found to be increased with increasing concentrations from 500 to 2000 ppm of both Vitex negundo and Catharanthus roseus methanol extracts as greenbased

corrosion inhibitors in both the E100 and E15 blend. Additions of Vitex negundo extract seem to be more effective than that of Catharanthus roseus extract to increase the corrosion-resistant properties of the mild steel both in pure E100 and E15 blend. The % corrosion inhibition efficiency was steeply increased with the additions of 500-1000 ppm of both plants extract and it attained an almost steady-state with the additions between 1000 and 2000 ppm of both plants. Maximum inhibition efficiencies of about 89 % and 75 % were obtained at 2000 ppm V. negundo and C. roseus extract, respectively, for the mild steel in E100, and it was about 86 % and 72 % in the E15 blend at 25 ± 2 °C in airtight condition. Especially, the corrosion-resistant properties of the mild steel in E100 and E15 blend with 1500 ppm and 2000 ppm V. negundo plant extract were found to be higher even than the corrosion-resistant properties in E0 after 1008-1344 hrs or more exposure times. Such high corrosion inhibition mechanism on the surface of the mild steel sheet by greenbased

corrosion inhibitors of V. negundo and C. roseus plant extracts in E100 and E15 biofuels was obeyed both the Langmuir and Temkin adsorption isotherms. Consequently, it can be said summarized that leaf extract of both plants act as good green-based inhibitors to minimize/control the electrochemical corrosion of the mild steel in E100 and E15 at room temperature.