Solanum melongena Peel Waste (Garden Egg Husk) as a Biogenic Inhibitor for Acid-Induced Corrosion of Carbon Steel

The development of green corrosion inhibitors from agro-waste materials presents a sustainable approach to mitigating acid-induced degradation of industrial metals. In this study, the inhibition efficiency of aqueous extract from Solanum melongena (garden egg) peel waste was systematically evaluated for carbon steel in 1.0 M hydrochloric acid using the weight loss (gravimetric) method for corrosion mitigation. Mild steel coupons were immersed in acidic solutions containing varying concentrations (100–400 ppm) of the extract for 24, 48, and 72 hours. The corrosion rate was calculated, and inhibition efficiency (%IE) determined as a function of extract concentration and exposure time. Results showed that the extract significantly reduced the corrosion rate of mild steel, with the highest inhibition efficiency of 47.89% recorded at 400 ppm after 24 hours. The inhibition efficiency increased consistently with both concentration and immersion duration, indicating a dose- and time-dependent protective effect. Adsorption studies revealed that the extract adhered strongly to the metal surface, following the Langmuir adsorption isotherm, which suggests monolayer physical adsorption of phytoconstituents such as polyphenols and flavonoids. These findings establish S. melongena peel extract as a potent, low-cost, and environmentally friendly corrosion inhibitor with promising applicability in industrial acid treatment processes.