Corrosion Inhibition Data and Statistical Analysis of the Performance of Rosemary Oil Extract on High Carbon Steel in Dilute Electrolyte Solutions

Abstract

Application of plant extracts for the corrosion protection of engineering materials is an ongoing research to replace the conventional toxic, costly and unsustainable chemical derivatives. Data on the corrosion inhibition performance of rosemary oil extracts on high carbon steel in 0.5 M C6H8O7, 0.5 M H2SO4 and 3.5 wt.% NaCl solution was studied and the inhibition efficiency data statistically analysed. The oil extract performed poorly in C6H8O7 solution with optimal inhibition efficiency of 49.21% at 1.5% extract concentration. However, the extract performed effectively in H2SO4 and NaCl solution with optimal inhibition efficiency of 78.45% at 2.5% extract concentration and 97.87% at 1.5% extract concentration. Inhibition efficiency varied significantly with exposure time and concentration. The oil extract exhibited chemisorption type adsorption mechanism in all the solutions in consonance with Langmuir, Frumkin and Freundlich adsorption isotherms. Statistical data on standard deviation showed the variation of extract inhibition efficiency with respect to mean inhibition value and exposure time was relatively significant in C6H8O7 solution due to instability of inhibitor molecules, compared to the relatively low values obtained in H2SO4 and NaCl solution. Data from numerical variation showed extract concentration is the dominant statistically relevant inducing inhibition performance of rosemary oil extract in C6H8O7 and NaCl solution with statistical relevance factor of 63.40% and 70.36% compared to the corresponding values obtained in H2SO4 solution were extract concentration and exposure time were statistically relevant. Data showed 30%, 19% and 90% of inhibition efficiency data in C6H8O7, H2SO4 and NaCl solution are above 70% inhibition value at margin of error of +0.09, +0.077 and +0.059.