Evaluating the Potential of Carica Papaya Leaves Extract as a Green Corrosion Inhibitor for Mild Steel in HCl Medium

Abstract Corrosion poses significant economic, environmental, and safety challenges in the oil and gas industry, particularly affecting pipeline integrity and longevity. Traditional synthetic corrosion inhibitors, while effective, often incur high costs and environmental drawbacks. Traditional synthetic inhibitors, such as sodium silicate have been used traditionally to manage corrosion but are risky to the environment and health. This study is aimed at evaluating the effectiveness and potential of Carica papaya leaves extract as a natural/green corrosion inhibitor for mild steel in Hydrochloric acid (HCl) medium and compares it to a synthetic inhibitor Sodium silicate (Na2SiO3) in simulated corrosive environments. The Carica papaya leaf extract (CPLE) was obtained using a Soxhlet apparatus with ethanol as the solvent for efficient extraction of bioactive compounds. Corrosion inhibition efficiency was determined through the weight loss method for a period of 15 days by exposing mild steel specimens to the corrosive medium that mimicked the environment and conditions of oil pipelines. Inhibition efficiency of the pawpaw leaf extract was compared to that of sodium silicate, which is a synthetic inhibitor. Some important parameters that were determined included corrosion rate, inhibition efficiency, and the effect of varying inhibitor concentrations (i.e., 0.3 g/L, 0.6 g/L, and 0.9 g/L). It was found that Carica papaya leaf extract (CPLE) demonstrates an improvement in inhibition efficiency with increasing concentrations but diminishes with prolonged immersion time. A maximal inhibition efficiency of 63.64%, 50.00%, 45.45%, 77.27% and 63.64% was observed for Carica papaya leaf extract (CPLE) at the concentrations of 0.3g/L, 0.6g/L, 0.9g/L, 1.2g/L, and 1.5g/L respectively, contrasting with sodium silicate's (Na2SiO3) peak efficiency of 45.45%, 40.00%, 27.27%, 63.64%, and 54.55% at 0.3g/L, 0.6g/L, 0.9g/L, 1.2g/L, and 1.5g/L concentrations respectively. Over time, for Carica papaya leaf extract (CPLE) demonstrated impressive durability; even after two weeks, it inhibited with a notable 55.00%, 50.00%, 46.97%, 74.48%, and 56.82% efficiency at the concentrations of 0.3g/L, 0.6g/L, 0.9g/L, 1.2g/L, and 1.5g/L respectively. In sharp contrast, sodium silicate (Na2SiO3) dwindled to 42.86%, 42.42%, 36.36%, 53.23%, and 57.14% efficiency at the concentrations of 0.3g/L, 0.6g/L, 0.9g/L, 1.2g/L, and 1.5g/L respectively by the end of the experiment. Results showed that the Carica papaya leaf extract (CPLE) successfully reduced the corrosion rate with maximum inhibition efficiency at high concentrations. Conversely, sodium silicate was found to be somewhat less efficient under the same testing conditions. The research also noted that inhibition efficiency reduced with longer immersion time, indicating the necessity for regular reapplication or more advanced inhibitor chemicals. Findings indicate that Carica papaya leaves extract exhibit significant inhibition efficiencies, offering environmentally friendly and cost-effective alternatives to synthetic inhibitors. This research emphasizes the potential for the application of Carica papaya leaf extract (CPLE) as a green and sustainable alternative for corrosion control in oil pipelines. By harnessing bio-based inhibitors, industries can reduce the application of toxic chemicals without affecting the anti-corrosive activity. This study underscores the potential of utilizing plant-based extracts in sustainable corrosion management strategies within the oil and gas sector. Future studies should involve the isolation of active constituents of the extract, optimizing the dosage, and assessing its performance and activity in different corrosive media.