Anti-corrosion Properties of Ethanol Extract of Cardiospermum halicacabum Leaf on Steel Pipelines in Acidic Environment

Abstract

In the continuation of the possibility of using green corrosion inhibitor, Cardiospermum halicacabum (CH) leaf extract as corrosion inhibitor for steel pipeline in 0.5 M hydrochloric acid using both gravimetric and potentiodynamic polarization techniques was investigated. The leaves were characterized by both quantitative and qualitative analyses and Fourier Transform Infrared Spectroscopy. Characterization of the substrates before and after corrosion tests were investigated by scanning electron microscope equipped with energy dispersive X-ray spectroscopy. The inhibitor concentration, time and temperature were varied in the range of 5–25% v/v, 1–12 days and 30–60 °C at 5% v/v, 2 days, and 10 °C interval,, respectively. Linear regression equation and analysis of variance (ANOVA) were employed to investigate the influence of process parameters (temperature, inhibitor concentration and time). Corrosion rate increased with the increasing temperature and decreased with increases in both inhibitor concentrations and time,, respectively. Maximum inhibition efficiency of 98.56% occurred at the optimal value of 20% v/v of the inhibitor concentration. The CH results revealed phytoconstituents such as tannins, alkaloids, saponins, flavonoids with their contents and azoddicarbonnamide, trphenyl phosphine oxide, etc. which were responsible for the protection of steel pipelines in acidic environment. The coupons without green inhibitor were rough, and severe pits and cracks occurred, while the surface of steel pipeline with green inhibitor was smooth. The adsorption of the molecules of the green inhibitor on adsorbate’s surface obeyed Langmuir adsorption isotherm. The potentiodynamic polarization results showed that the green inhibitor acted as mixed-type inhibitor. The ANOVA results also showed that inhibitor concentration was the most important and followed over time for the anti-corrosion of the steel pipeline by the green inhibitor.