Dimeric imidazolium ionic liquids connected by bipyridiyl as a corrosion inhibitor for N80 carbon steel in HCl

Abstract

A new type of the dimeric imidazolium-type amphiphile, BDBCmIB (m = 1, 4 and 8), was synthesized using the bipyridiyl as the spacer, and its inhibition performance and mechanism for the corrosion of N80 carbon steel in 1.0 mol·L−1 HCl were evaluated using chemical and electrochemical measurements, surface analyses and density functional theory (DFT) calculations. Results show that the inhibition efficiency of BDBCmIBs increases with their concentrations and the length of tail chains. BDBC8IB exhibits the best inhibition performance among them and its inhibition efficiency almost exceeds 90% in a wide concentration range from 1.0 × 10−6 to 5.0 × 10−4 mol·L−1 mol·L−1 at 25.0 °C, which attains the maximum over 95% at 5.0 × 10−4 mol·L−1. Moreover, three BDBCmIBs all display the high inhibition efficiency at 5.0 × 10−4 mol·L−1, nearly exceeding 90%, in the temperature range from 25.0 to 55.0 °C. As a mixed-type inhibitor, BDBCmIBs can retard both cathodic hydrogen evolution and anodic metal dissolution processes, since BDBCmIB molecules bear the imidazolium-based heterocycle with the electron-donating ability and the bipyridine with the electron-accepting ability, thereby facilitating the formation of a protective film on the surface of N80 carbon steel via electrostatic interactions, coordinated and back-donating bonds. The adsorption of BDBCmIBs obeys the Langmuir isothermal model. Our finding demonstrates that the introduction of the bipyridiyl at the spacer does favor improving the inhibition efficiency of such dimeric imidazolium-type amphiphiles, and meanwhile, the proper increase in the number of carbon atoms in the substituents on the imidazole rings can also enhance the inhibition efficiency.