Thesis (B.S.) -- Cagayan State University, 2025.

Corrosion is a natural process that deteriorates the metal's surface by chemical or electrochemical reaction with its environment. Traditional corrosion inhibitors pose significant environmental and health risks due to their toxicity. On the other hand, the utilization of green corrosion inhibitors as efficient, economical, and environmentally friendly has accumulated interest in the field of corrosion protection. The study aimed to determine the corrosion inhibition of Kamias (Averrhoa bilimbi L.) fruit ethanolic extract on mild steels in IM HCl solution. The phytochemical components of Kamias fruit responsible for preventing corrosion were extracted using ethanol by maceration method. The effectiveness of the extract was examined using weight loss method and surface morphology of the corroded metal surface. The findings demonstrated that Kamias fruits' ethanolic extract effectively inhibits corrosion of mild steel in HCI. The addition of extract reduced the corrosion rate, with the optimum inhibition efficiency at 76.39% observed at 0.3g/mL concentration. However, lower concentration and longer immersion time decreased its effectiveness. SEM images show the protective layer formed by the extract which reduced the surface roughness of mild steels. Additionally, the extract's corrosion inhibition at 0.3g/mL concentration was comparable to that of primer. Therefore, the ethanolic extract of Kamias (Averrhoa Bilimbi L.) fruit serves as an effective corrosion inhibitor of mild steel in hydrochloric acid media.

Keywords: Kamias fruit, corrosion, inhibition efficiency, mild steel, SEM