**3. Conclusion**

On the basis of the above discussion of the alkylation effect on ionic liquids in various analyses, it can be concluded that structural effect is a considerable key factor in enhancing corrosion protection performance of metal in acid medium. Alkylation of the heterocyclic cation in the ionic liquid, particularly on N1/N2 of imidazolium, benzimidazolium, or N1 of pyridinium or P1 phosphonium, facilitates the physical/chemical properties of the ionic liquids compared to unalkylated ionic liquid. Not only had the physical/chemical properties changed but also electrochemical properties. This effect has been discussed with respect to various studies, such as electrochemical behavior, surface protection, electronic properties quantum chemical analysis (QCA), and hydrogen gas evolution. Adsorption of ionic liquid is favored mostly when it is being structurally modified as a result of passive film adsorption on the metal surface, which keeps the environment corrosion free. The reason for the extraordinary maturity of the alkylated ionic liquid could be described using theoretical study. This will support the alkylated or structurally modified ionic liquid electronic properties. The electron-donating nature of ionic liquid is being increased by alkylation. As a result, the resonance effect also increased, which contributes to the stability of the ionic liquid compared to the unalkylated form. The use of ionic liquid as a corrosion inhibitor is predominant and more efficient for structural modification.
