Anti-corrosion Properties of Ethanol Extract of Acacia senegalensis stem on Al–Si–Fe/SiC Composite in Sulfuric Acid Medium

Abstract

The potential of Acacia senegalensis stem extract for corrosion inhibition of aluminum alloy (Al–Si–Fe) reinforced with 15% SiC in 0.5 M H2SO4 was investigated using gravimetric and potentiostatic polarization techniques. The plant stems were characterized by both FT-IR and GC–MS with the aims of knowing the active components. The concentration of inhibitor, temperature and time were varied in the range of 0–10% v/v at 2% v/v interval, 30–70 °C at 20 °C interval and 12–72 h at 12 h interval, respectively. The surface morphology of the coupons before and after corrosion tests were characterized by scanning electron microscopy (SEM) techniques. The results of both weight loss and potentiostatic polarization indicated that the corrosion inhibition efficiency increased with an increase in inhibitor concentration at optimum of 8% v/v (92.66% at 30 °C) and decreased with an increase in temperature at 50 °C (89.61%) and at 70 °C (79.98%). Both the adsorption and physisorption followed Langmuir adsorption isotherm. SEM shows a smooth morphology for the specimens after immersion in 0.5 M H2SO4 solutions containing 8% v/v optimum of Acacia senegalensis. The FT-IR and GC–MS results revealed some elements (−N=C=S, C≡N), chemical bonds/functional groups (NH2) which were responsible for the protection of aluminum alloy (Al–Si–Fe) reinforced with 15% SiC in acid environment. High inhibition efficiency was obtained, which suggests that the extract could serve as an effective inhibitor of the composite in 0.5 M sulfuric acid.