Moringa oleifera Extract as a Green Corrosion Inhibitor for API 5L in Seawater Medium: Electrochemistry and Surface Study
摘要
Corrosion inhibitors for API 5L steel pipes in marine environments must be effective, thermally stable, and environmentally friendly. Based on these concerns, this study aimed to comprehensively evaluate M. oleifera extract based on concentration, temperature, and time on API 5L steel in marine environments. Potentiodynamic polarisation results indicate that the corrosion current density (Icorr) decreases from 61.14 µA cm−2 to 13.38, 11.18, and 5.35 µA cm−2 at inhibitor concentrations of 100, 200, and 300 mg L−1, respectively. The corrosion rate (CR) dropped from 27.94 mpy to 2.45 mpy (~ 91% IE), while the charge transfer resistance (Rct) increased from 11.03 Ω cm2 to 118 Ω cm2 with 300 mg L−1 of M. oleifera. The inhibitor performed effectively at elevated temperatures, with efficiencies of 89.16% at 308 K and 87.72% at 318 K. The data indicate that the adsorbed protective film exhibited stability at elevated temperatures, with ΔGads = –29.5 kJ mol−1 and Ea = 19.47 kJ mol−1 in the presence of 300 mg L−1 of M. oleifera. The present study on immersion time revealed that the film was produced rapidly, with inhibition efficiencies > 91% at initial exposure and > 88% after 60 min. SEM-EDX and 3D optical profilometry results also confirmed that the addition of M. oleifera showed a reduction in damage and surface roughness. XPS analysis revealed the presence of Fe–O and Fe–C bonds, confirming the formation of a stable iron-organic protective layer. GC-MS and FT-IR spectra results indicated that fatty acids and phenolic compounds containing heteroatoms were suspected to be responsible for adsorption and corrosion inhibition. The findings indicate that M. oleifera leaf extract inhibited corrosion by ~ 91% at low concentrations (≤ 300 mg L−1) and maintained performance over a temperature range of 298–318 K, highlighting its potential for marine and offshore pipeline applications.
Graphical Abstract