Corrosion Inhibition Efficiency of Steel by Mango Peel Extract in Hydrochloric Acid at Different Temperature

Nowadays, researchers are interested in exploring the possibility of replacing harmful inorganic chemicals with green organic substances derived from natural sources. This study focuses on accessing the potential of a green corrosion inhibitor for mild steel, using plant extracts from local mango peel. The Harumanis mango peel leftover was extracted using solvent extraction techniques and the chemical compounds were characterized through Fourier Transform Infra-Red (FTIR) and UV-visible spectroscopy. The analysis showed that the crude extract of Harumanis mango peel (HMPE) contained active functional groups for corrosion inhibitory properties such as -OH, -COOH, -C=O and aromatic ring structure. The presence of mangiferin and other flavonols, likely acid gallic, was also detected. The efficiency of HMPE as a corrosion inhibitor for mild steel was investigated through a conventional corrosion test. The immersion test was carried out in different temperatures at 30, 40, 50 and 60 ⁰C with and without the addition of the 50 to 350 ppm HMPE inhibitor in 1 M hydrochloric acid, HCl. The result showed that the corrosion inhibition efficiency for mild steel in acidic medium increased as the concentration of the Harumanis mango peel increased. The maximum inhibition efficiency of 85 % was obtained at 30 ⁰C for 300 ppm. The adsorption of the Harumanis mango peel corrosion inhibitor obeys Langmuir isotherm model. The adsorption of HMPE on mild steel showed comprehensive (mixed) types as revealed by thermodynamic studies. Favourable adsorption was more dominant for 30 and 40 ºC inhibitors system, whereas at high temperatures the adsorption showed weak and unfavourable interaction between HMPE and the mild steel surface. Surface analysis showed the mild steel surface was free from pits and uniform corrosion as it was inhibited by the HMPE in low temperature solution.