Calotropis procera Latex Extract as an Effective Green Corrosion Inhibitor for Mild Steel in Acidic Medium: Experimental and Quantum Chemical Approaches

In this work, Calotropis procera latex extract (CPLE) was evaluated as an environmentally benign corrosion inhibition on mild steel in 1-M HCl using gravimetric, electrochemical, surface, and computational approaches. The results revealed that CPLE exhibited an efficient corrosion inhibitor with the efficiency of 94.26% and 93.10% at 200-ppm concentration from electrochemical and weight loss studies, respectively, and the deviation between these results is within the accepted uncertainty due to the methods used as well as experimental error. A weight loss study revealed that the effectiveness of plant extracts increases as their concentration increases. The effect of temperature on corrosion behavior was studied using the optimal concentration of CPLE in the temperature range of 303–333 K. As the temperature rises, the inhibitory efficiency decreases. Potentiodynamic polarization results disclose that CPLE acts as a mixed-type inhibitor. CPLE inhibits metal corrosion via an adsorption mechanism and followed by the Langmuir adsorption isotherm. Molecular dynamics (MD) simulations confirm that all four molecules—3,7,10-trimethyl pentadecane-ol, hydroxy hexanone, decene, and triisopropyl benzene—adsorb partially parallel on Fe(110) with interaction energies aligning with DFT trends, identifying 3,7,10-trimethyl pentadecane-ol as the strongest inhibitor. Surface studies such as AFM, SEM, FTIR spectroscopy, and UV-visible confirmed the adsorption-mediated corrosion inhibition. DFT study reveals that 3,7,10 trimethyl pentadecane-ol is the most effective component of CPLE extraction to interact with metal surface.