Dimeric imidazolium ionic liquids connected by bipyridiyl as a corrosion inhibitor for N80 carbon steel in HCl
A new type of the dimeric imidazolium-type amphiphile, BDBC m IB (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 BDBC m IBs increases with their concentrations and the length of tail chains. BDBC 8 IB 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 BDBC m IBs 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, BDBC m IBs can retard both cathodic hydrogen evolution and anodic metal dissolution processes, since BDBC m IB 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 BDBC m IBs 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.
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