Umudike Journal of Engineering and Technology

Corrosion of mild steel in acidic environments remains a major challenge in many industrial applications, increasing the demand for sustainable and environmentally friendly corrosion inhibitors. This study investigated the corrosion inhibition performance of Annona muricata leaf extract (SSOP), Citrus sinensis peel extract (ORG), and their hybrid formulations in hydrochloric acid using the gravimetric weight-loss method. Corrosion rate, inhibition efficiency, and surface coverage were evaluated over an immersion period of 24–144 h. The results showed that all inhibitor systems significantly reduced the corrosion rate compared with the uninhibited solution. Among the tested formulations, the 20:80 (ORG/SSOP) hybrid exhibited the best performance, reducing the corrosion rate by approximately 41% and 8.1% relative to SSOP and ORG, respectively. The individual ORG and SSOP extracts recorded inhibition efficiencies of approximately 96.2% and 94.2%, respectively and achieving the highest inhibition efficiency of about 96.5%. Surface coverage measurements indicated that this formulation formed the most stable protective film on the mild steel surface throughout the exposure period. The superior performance of the 20:80 (ORG/SSOP) blend suggests a synergistic interaction between the plant extracts, resulting in enhanced adsorption and corrosion protection. These findings demonstrate the potential of the hybrid extract as an effective and eco-friendly corrosion inhibitor for mild steel in acidic environments.