Acacia Mollissima Tannins: Insights into Corrosion Resistance and Thermal Pyrolysis Kinetics
摘要
To mitigate the environmental impacts of harmful chemical substances, tannin has emerged as an eco-friendly corrosion inhibitor in acidic media. The condensed tannin was extracted from Acacia Mollissima and characterized using IR, XRD, and SEM. This paper explores the corrosion inhibition effect of tannin on mild steel in 1 M HCl using corrosion potential (Ecorr), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) across temperatures ranging from 303 to 343 K. Results demonstrate that tannin effectively inhibits corrosion in HCl, with its efficiency increasing with concentration but decreasing with temperature. Additionally, this research aims to extract thermal and kinetic data from tannin sourced from Acacia Mollissima, employing thermogravimetric analysis across four heating rates. Thus, the mass loss' second derivative DDTG was used to determine the characteristic decomposition temperatures precisely and to compare the thermal stability. The kinetic parameters, including activation energy and pre-exponential factor, were obtained using four isoconversional model-free methods proposed by Kissinger, Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Friedman. The energy required for degradation is higher at the final stages, indicating the presence of stable oxides at high temperatures. Using the Kissinger technique, the activation energy and pre-exponential factor were determined to be 301 kJ/mol and 6.9537 × 1025 min−1, respectively. In contrast, the average activation energy for free model approaches is 87.48, 82.66, and 82.97 kJ/mol when utilizing the FWO, KAS, and Friedman methods. Then, the most probable reaction functions were determined using the Coats-Redfern method, resulting in significantly improved calculation performance across the entire conversion range.