Influence of ring size on corrosion inhibition potential of environmental sustainable cycloalkyltriphenylphosphonium based ionic liquids: Computational and experimental demonstrations

Background: Corrosion mitigation potential of environmental sustainable cycloalkyltriphenylphosphonium based ionic liquids, namely, cyclopentyltriphenylphosphonium bromide (CPTPB), cyclohexyl triphenylphosphonium Bromide (CHTPB), differing in the size of cycloalkyl rings was demonstrated for mild steel corrosion in 0.5 M H2SO4. Methods: Electrochemical (EIS and PDP), surface (SEM and AFM) and computational modelings (DFT and MDS). Findings: Results suggest that CHTPB containing cyclohexyl ring exhibits superior inhibition potential as compared to the CPTPB containing cyclopentyl ring. CPTPB and CHTPB exhibit highest protection potential of 99.36% and 99.52%, respectively at 10−2 M. Both the inhibitors are mixed type of inhibitors. Potentiostatic polarization (PP) study showed that passivation was observed only at lower concentrations due to a synergistic effect. Adsorption mechanism of CPTPB and CHTPB was best explained using the Langmuir adsorption isotherm. Surface morphologies of protected metallic specimens were greatly enhanced due to the formation of protective film by CPTPB and CHTPB. MDS and DFT based computational analyses were support the experimental outcomes.