Surface interaction of expired Brilcure (Ticagrelor) drug on soft-cast steel in 0.5 M H2SO4 medium: Corrosion protection, surface characterizations and computational studies

•Expired Ticagrelor was investigated as a corrosion inhibitor for soft cast steel in acidic media.•Ticagrelor demonstrated a maximum inhibition efficiency of 98.99 % at 250 ppm in 0.5 M H2SO4.•The adsorption of Ticagrelor on the mild steel surface followed the Langmuir isotherm model.•Advanced microscopy techniques confirmed a protective layer formation on the steel.•Theoretical studies and molecular simulations elucidated the inhibitor's efficiency and stability. Soft-cast steel (SCS) is extensively used in industry but is prone to corrosion in acidic solutions, necessitating effective protection methods. Corrosion inhibitors offer a rapid, easy, and economical solution. However, expired ticagrelor (Brilcure) poses environmental risks when discarded due to its active components. Therefore, this study explores the use of expired ticagrelor (TCGL) to prevent SCS corrosion in sulfuric acid, utilizing its active components, such as N and O atoms and conjugated bonds, as adsorption centers while being environmentally friendly. The corrosion inhibition and adsorption properties of TCGL on SCS in 0.5 M H2SO4 were investigated using weight loss, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) techniques. Surface characterization of SCS was performed using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), atomic force microscopy (AFM), and water contact angle (WCA) measurements. The adsorption behavior of TCGL followed the Langmuir isotherm model. Additionally, density functional theory (DFT) and molecular dynamics (MD) simulations were employed to elucidate the bonding interactions between TCGL and the metal surface. Ticagrelor achieved 98.99 % inhibition efficiency at 250 ppm by adsorbing on the steel surface, forming a protective film. PDP studies showed decreased corrosion current density and a potential shift from -0.53 V to -0.49 V. SEM and AFM confirmed significant protection. DFT and MD simulations identified active sites and molecular mechanisms, highlighting Ticagrelor's potential as an effective, eco-friendly corrosion inhibitor for SCS. [Display omitted]