Weight loss, potentiodynamic polarization (PDP), linear resistant polarization (LPR) and electrochemical impedance spectroscopy (EIS) methods were used to investigate the inhibition potentials of various concentrations of 4-hydroxylbenzoic acid for mild steel corrosion in 0.1 M H₂SO₄. The surface morphology of the metal was studied using scanning electron microscope (SEM) while the Fourier transformed infra-red spectrophotometer was used to identified the functional groups participating in the inhibition process. Experimental results indicated that the inhibition efficiencies of 4-hydroxylbenzoic acid obtained from weight loss, PDP, LPR and EIS measurements at 303 K ranged from 56.21 to 69.35%, 81.03 to 91.03%, 68.17 to 94.64% and from 97.42 to 99.44% respectively. The inhibition efficiency exhibited a progressive increase with increase in concentration and a corresponding decrease with temperature. The SEM micrographs of the metals’ surface, in the presence of the inhibitor revealed smoothness of the metal’s surface through inhibition. Some functional groups of the inhibitor were missing; some were re-characterized by shifts in frequency of absorption while few new bonds were formed. The adsorption of 4-hydroxyl benzoic acid supported physical adsorption mechanism because the inhibition efficiency increases with temperature and the range of values obtained for the activation energy (41.40 to 66.22 J/mol) and the standard free energy of adsorption (-10.87 to -11.67 J/mol) were within the expected range for physiosorption. Calculated values of some electronic parameters were within the range of values expected for some known and efficient corrosion inhibitors while Results obtained from computational chemistry modeling are in strong agreement with experimental results.

Keywords: Corrosion; Mild Steel; Inhibition; 4-Hydrobenzoic Acid;