Corrosion inhibition of API 5L X-52 pipeline steel in oilfield acidizing solution by gentamicin and sulfamethoxazole: experimental, plane-wave density functional theory (PWDFT) and the generalized-gradient approximation (GGA) simulations

We present the use of gentamicin (GENTA) and sulfamethoxazole (SULFA) for carbon steel corrosion protection in HCl solutions using weight loss, electrochemical impedance spectroscopy, potentiodynamic polarization techniques, molecular dynamic simulations plane-wave density functional theory (PWDFT) and the generalized gradient approximation, (GGA). The surface morphologies were examined using scanning electron microscopy (SEM). The potentiodynamic polarization test showed that GENTA and SULFA are mixed-type inhibitors with maximum achievable inhibition efficiency of 90% and 80%, respectively at 500ppm. SEM analysis further confirmed the inhibitory action of GENTA and SULFA on carbon steel. Molecular simulations reveal two stable adsorption configurations on the Fe (110) surface for GENTA and SULFA which were identified after geometry optimization using PWDFT and the GGA. The presence of the delocalized g-electrons of the aromatic rings provided extra stability to the configurations with flat adsorption orientations on the Fe (100) surface. The inhibitor adsorption energies and electronic properties correlate well with the experimental results.