Custard apple leaves extract as sustainable corrosion inhibitor for mild steel in 5% HCl.

AbstractA water-soluble extract of custard apple leaves (CALEX) was obtained and characterized using detailed spectral analytical techniques. A comprehensive corrosion mitigation performance study was undertaken to examine the CALEX as efficacious inhibitor for mild steel (MS) in a 5% HCl solution employing weight loss (WL), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Weight loss study was conducted over the temperature range of 298–328 K at the CALEX concentration range of 10–100 ppm. With the increase in CALEX concentration in the HCl solution the inhibition efficiency (%I.E.) increased but declined with increase in temperature. EIS revealed that the <italic>Rct</italic> value increases and PDP showed the mixed-type inhibition mechanism. Surface analysis presented amelioration in the surface morphology of CALEX treated MS, revealing establishment of absorptive protective film by the different organic compounds present in CALEX. XPS technique was used to understand the chemical makeup and bonding state of the CALEX molecules with the MS surface. The contact angle measurement suggested improved hydrophobicity for the CALEX inhibited MS sample compared to uninhibited sample. The adsorption of compounds present in CALEX was observed to be in line with the Langmuir adsorption isotherm. [ABSTRACT FROM AUTHOR]