Interfacial adsorption behavior of quaternary phosphonium based ionic liquids on metal-electrolyte interface: Electrochemical, surface characterization and computational approaches

Abstract

In present study two quaternary phosphonium salts namely (1-NapthylMethyl)-triphenylphosphonium Chloride (1-NpMe-TPC) and (4-Methoxybenzyl)-triphenylphosphonium Bromide (4-MeOBz-TPB) are reported as inhibitors for mild steel (MS) corrosion in 0.5MH2SO4 using various electrochemical, theoretical and surface morphological techniques. Inhibitors 1-NpMe-TPC and 4-MeOBz-TPB were prepared by diluting the solution of concentration 10−2 to 10−5M and results are showed maximum efficiencies of 99.72% and 97.76%, respectively at 10−3M concentration (298K). Polarization measurements revealed that both 1-NpMe-TPC and 4-MeOBz-TPB acted as mixed corrosion inhibitors. EIS study revealed that 1-NpMe-TPC and 4-MeOBz-TPB adsorbed at the mild steel/0.5M H2SO4 interfaces and enhanced the magnitude of charge transfer resistances. Adsorption of the 1-NpMe-TPC and 4-MeOBz-TPB at the metallic surface was further supported by SEM and AFM studies. Several thermodynamic parameters (ΔGads0, ΔHads0 and ΔSads0 ), Semi-empirical AM1 and MD parameters were derived in order to describe the adsorption behavior of 1-NpMe-TPC and 4-MeOBz-TPB on metallic surface. The reasonable consistence was found between experimental and theoretical results.