Evaluation of the corrosion inhibition of Senna occidentalis and Polyalthia longifolia leaves extracts on reinforced steel in 2m HCl solution

Abstract

Corrosion of reinforced steel in acidic environments poses significant challenges in industrial and construction applications. This study evaluates the corrosion inhibition performance of Senna occidentalis and Polyalthia longifolia leaf extracts on reinforced steel in 2 M HCl at 303 K over an immersion period of 24 hours. Extracts were prepared via maceration and tested individually and in combination. Corrosion rates and inhibition efficiencies were determined using the weight loss method, while FTIR and SEM analyses were used to characterize functional groups and surface morphology. Results show that Senna occidentalis and Polyalthia longifolia extracts achieved
inhibition efficiencies of 71% and 81%, corresponding to corrosion rates of 3.8 mm/year and 3.3 mm/year, respectively. In contrast, the combined extract exhibited a significantly higher inhibition efficiency of 98% and a markedly reduced corrosion rate of 0.36 mm/year. This represents a ~17– 27% improvement in efficiency and over 10-fold reduction in corrosion rate compared to individual extracts. The enhanced performance of the combined extract is attributed to synergistic interactions among phytochemical constituents, leading to improved adsorption and protective film formation on the steel surface. These findings highlight the potential of these plant extracts as effective, eco-friendly, and sustainable corrosion inhibitors.