Eco-friendly 2-Thiobarbituric acid as a corrosion inhibitor for API 5L X60 steel in simulated sweet oilfield environment: Electrochemical and surface analysis studies

The corrosion inhibition efficiency of 2-Thiobarbituric acid (TBA) for metal substrate (API X60 steel) in 3.5% NaCl solution saturated with CO₂ gas was probed using various techniques namely, LPR (linear polarization resistance), EIS (electrochemical impedance spectroscopy), and PDP (potentiodynamic polarization). The effects of TBA concentration (25–100 ppm), solution pH (4 and 6), temperature (25–80 °C), and immersion time (2–72 h) on the inhibition efficiency were examined. SEM (scanning electron microscopy) and XPS (X–ray photoelectron spectroscopy) were deployed to explore the corrosion retardation mechanism. TBA exhibited protection efficiencies exceeding 90% for all experimental conditions considered. The excellent anticorrosion performance by TBA was retained up to 72 hours of immersion time. PDP results exhibited that TBA behaved as a mixed type inhibitor. Results from kinetics and thermodynamics analyses indicate that TBA chemically adsorbed on the steel surface following Langmuir isotherm model. The composition of the adsorbed TBA film has been analyzed by XPS.