BaNb0.5In0.5(PO4)2 as an Efficient Inorganic Inhibitor for Mild Steel Corrosion in Acidic Media: Insights from Electrochemical Techniques and Surface Analyses
Ahmed Griech, Marouane El-Alouani, Sami M. Alharbi, Zaidi Abderazzak, Issam Saber, Khattabi Mohamed, Khadija Dahmani, Mouhsine Galai, Helal S. Alharbi, Rachid Fakhreddine, Rida Allah Belakhmima, Mohamed Ebn TouhamiA novel orthophosphate compound, BaNb0.5In0.5(PO4)2 (FA31), was investigated as a corrosion inhibitor for mild steel in 1.0 M HCl using electrochemical techniques, adsorption studies, and surface characterization. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) measurements demonstrated that the inhibition efficiency increased with inhibitor concentration, reaching a maximum value of 94.8% at the optimal concentration. The charge-transfer resistance (Rct) increased significantly from that of the uninhibited solution to 427.2 Ω·cm2 in the presence of FA31, indicating the formation of a protective interfacial layer that effectively suppressed the corrosion process. The adsorption of FA31 on the mild steel surface followed the Langmuir adsorption isotherm, while the calculated standard Gibbs free energy of adsorption (ΔG°ads) indicated that the inhibition process was predominantly governed by physisorption. SEM/EDS analyses further confirmed the formation of a compact and homogeneous protective film on the steel surface. The combined electrochemical and surface analyses demonstrate that FA31 is an effective and environmentally promising corrosion inhibitor for mild steel in acidic media.