The adsorption behavior and inhibitive action of hydrocotyle umbellata leaf extract on corrosion of API5L L360 carbon steel in 0.5 M H2SO4 solution
摘要
In the present work, Hydrocotyle umbellata leaf extract (HUL) was used as a potential corrosion inhibitor for API 5L L360 carbon steel (L360CS) in a 0.5 M sulfuric acid medium. The study employed various techniques, including chemical and electrochemical measurements, surface morphological analyses, and computational methods such as Density Functional Theory (DFT), to investigate the adsorption behavior and corrosion inhibition efficiency of HUL on the L360CS surface in an acidic environment. Using the Weight Loss (WL) method, increasing the temperature from 25 to 45 °C at the same 180 ppm concentration resulted in efficiencies of 93.5% and 88.2%, respectively. Activation energy (E*a) calculation using the Arrhenius equation shows an increase in activation energy upon adding the HUL extract: 0.5 M H2SO4 (E*a = 27.2 kJ mol-1), and the maximum activation energy (E*a = 58.9 kJ mol-1) was observed for the 180 ppm HUL extract in the acid medium. The adsorption behavior has been analyzed, revealing a predominantly physical interaction, with Gibbs free energy calculations (ΔG°) of – 24.6 kJ mol−1 at 25 °C. The inhibitory action is attributed to the spontaneous physicochemical adsorption of the HUL onto the L360CS surface, a process that conforms to the Langmuir adsorption isotherm. Using EIS measurements, a maximum percent inhibitory effectiveness of 95.9% was achieved for 180 mg/L solutions. The polarization curves showed that the HUL extract acts as a mixed-type inhibitor. The study employed various techniques, including chemical and electrochemical measurements and computational methods such as Density Functional Theory (DFT), to investigate the adsorption behavior and corrosion inhibition efficiency of HUL on the L360CS surface in an acidic environment. A probable inhibitive mechanism is proposed from the viewpoint of adsorption theory.