Optimization of Blended Fig and Gmelina (Ficus Polita and Gmelina Arborea) Leaves Extract as Corrosion Inhibitor of Steel in Hydrochloric Acid

The world is currently exploring alternatives that are environmentally friendly in different fields and corrosion engineering has notbeen left out. Numerous plant extracts have been investigated as alternatives to inorganic inhibitors for their potential use as corrosion inhibitors in various industries. Research in this area is receiving a lot of interest in developing inhibitors with promising results as reported by several researchers. This work focused on optimization of combined Ficus polita and Gmelina arborea leaf extracts as corrosion inhibitor for low-carbon steel in 1M%HCI using gravimetric techniques. The leaves extracts were subjected to phytochemical screening and Fourier Transform Infrared Spectroscopy analysis (FTIR). Scanning Electron Microscopy (SEM) was performed on protective layer. Stat-Ease Design Expert was used for design of the experiment and the analysis of the results. Immersion time, Temperature and Inhibitor Quantity were considered as design factors, while the HCI was constant throughout the experiments. Inhibition efficiencies were measured using the IE formula. The results showed that the extracts contained alkaloids, flavonoids, tannins, steroids, saponins, terpenoids, phenols, and functional groups, which were responsible for the corrosion-inhibitory action of the extracts. Scanning Electron Microscopy (SEM) revealed that the surface of low-carbon steel was significantly less corroded in the presence of the blended extracts compared to the control sample. This confirmed the formation of a protective layer on the steel surface. The weight loss results indicated that the blended extract reduced the corrosion rate. The optimal conditions were an immersion time 24h, temperature of 30 ℃, inhibitor ratio of 30:70, inhibitor quantity of 0.6g and Inhibitor Efficiency of 95.08%. These results showed that the blended extract could serve as a good substitute for industrial inhibitors.