Inhibitive action of Carica papaya extracts on the corrosion of mild steel in acidic media and their adsorption characteristics

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Abstract
Purpose: To evaluate the effect of different parts of Carica papaya (leaves (LV), seeds (SD), heart wood (HW) and bark (BK)) as eco‐friendly and non‐toxic mild‐steel corrosion inhibitors in H2SO4 at 30 to 60 oC.Design/methodology/approach: Acid extracts of the different parts of Carica papaya were used as inhibitors in various corrosion tests. Gravimetric and gasometric techniques were used to characterise the mechanism of inhibition.Findings: The LV, SD, HW and BK extracts were found to inhibit mild steel corrosion in H2SO4. The inhibition efficiencies of the plant's part extracts follow the trend: LV > SD > HW > BK. Inhibition efficiency increased with extracts concentration but decreased with temperature. Physical adsorption of the phytochemical components of the plant on the metal surface is proposed as the mechanism of inhibition. The experimental data fits well into the Langmuir and Temkin adsorption isotherms.Practical implications: The plant extracts can be used in chemical cleaning and picking processes.Originality/value: The research provides information on the possible use of the different parts of Carica papaya as sources of cheap eco‐friendly and non‐toxic corrosion inhibitors.