Synthesis and Investigations of Corrosion Inhibition Performance of an Ester and Acid α-Hydroxyphosphonates Combining Experimental, Density Functional, and Monte Carlo Methods

[Hydroxy(4-methoxyphenyl) methyl]-phosphonate acid (H4MPMPA) and diethyl-[hydroxy(4-methoxyphenyl) methyl] phosphonate (DH4MPMP) were synthetized. Chemical and electrochemical techniques were used to examine their effectiveness at preventing XC48 corrosion when exposed to HCl. The weight loss method demonstrate the production of a protector film that obey to Langmuir isotherm, the polarization measurements prove that the inhibition process are mixt, and EIS shows that the efficiencies rise in parallel with the inhibitors’ concentration. According to AFM, the corroded XC48’s average roughness (360.5 nm) was higher than that obtained in the presence of DH4MPMP or H4MPMPA 169.78 and 60.70 nm, respectively. DFT calculates several thermodynamic and electronic parameters and investigates whether electron transfer affects inhibition. It also reveals that the nucleophile and electrophile zones are situated around oxygen and hydrogen atoms respectively. MDS simulates the interface configuration, demonstrating interfacial distances of 2.84/3.67 and 3.02/3.08 Å for Fe–O/Fe-π of H4MPMPA and DH4MPMP respectively, supporting mixt process at these distances.