Novel Pyrimidine‐5‐Carbonitriles as Potential Green and Sustainable Corrosion Inhibitor for Mild Steel in Acidic Medium: Experimental and Theoretical Approaches

ABSTRACT In this study, three pyrimidine‐5‐carbonitrile derivatives (PNs) were synthesized using a one‐pot multicomponent reaction involving malononitrile, aromatic aldehydes, and an amidine derivative in an aqueous glucose solution as a fully green medium are 2,4‐diamino‐6‐phenylpyrimidine‐5‐carbonitrile (PN‐1), 2,4‐diamino‐6‐(4‐methoxyphenyl) pyrimidine‐5‐carbonitrile (PN‐2), and 2,4‐diamino‐6‐(4‐nitrophenyl) pyrimidine‐5‐carbonitrile (PN‐3). The simulated LD50 values of 430, 1300, and 900 mg kg −1 for PN‐1, PN‐2, and PN‐3, respectively illustrate their nontoxic and environmentally benign properties. The corrosion protection effectiveness of all three PNs over mild steel in 1 molar hydrochloric acid was evaluated using gravimetric, electrochemical, potentiodynamic polarization, surface analysis, density functional theory (DFT), and molecular dynamics simulations (MDS). PN‐3 has a maximal inhibitory efficiency of 97.6% at 308K at a concentration of 50 mg L −1 . PNs adsorption follows the Langmuir adsorption isotherm, with ΔG 0 ads values of −37.75, −39.46, and −39.94 kJ mol −1 for PN‐1, PN‐2, and PN‐3, respectively, indicating spontaneous chemisorption and physisorption at the metal surface. Surface examination revealed the presence of a preventative barrier on the mild steel surface. Furthermore, DFT and MDS were used to validate the experimental results. MDS shows that all three PNs adsorb partially parallel to the Fe (110) surface. Their interaction energies are consistent with DFT studies, identifying PN‐3 as the most potent inhibitor.