Hydroquinone Decorated with Alkyne, Quaternary Ammonium, and Hydrophobic Motifs to Mitigate Corrosion of X-60 Mild Steel in 15 wt.% HCl

1-(6-Bromohexyloxy)-4-propargyloxybenzene upon quaternization with 3-dimethylamino-1-propanol and N,N-dimethyldodecylamine produced two new inhibitor molecules: N-[6-(4-Propargyloxyphenoxy)hexyl]-N,N-dimethyl-N-(3-hydroxypropyl)ammonium bromide (PHAB) and N-[6-(4-Propargyloxyphenoxy)hexyl]-N,N-dimethyl-N-dodecylammonium bromide (PDAB), respectively, in excellent yields. The inhibitor molecules were characterized by elemental analysis, Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR spectroscopy. The inhibitors were evaluated for X-60 mild steel corrosion in 15 wt.% HCl using different electrochemical and gravimetric techniques. The potentiodynamic polarization confirms both the inhibitors as mixed-type corrosion inhibitors. A low concentration (15 ppm) of PDAB has demonstrated excellent corrosion inhibition efficiencies of 97%, 98%, and 86% at 25 °C, 50 °C, and 70 °C, respectively, for 24 h exposure time. SEM and EDX spectra reveal that the adsorptions of corrosion inhibitors on X-60 mild steel create a protective film that serves as a barrier to mitigate the corrosion process. The X-ray photoelectron spectroscopy confirmed the chemical interaction between the corrosion inhibitors and mild steel, which was predicted by the Langmuir adsorption model. Assembly of inhibitive motifs of the alkyne, π-electron-rich aromatic, quaternary ammonium and C₁₂ alkyl chain hydrophobe in PDAB has augmented its inhibiting action.