Study Of Mercaptobenzimidazoles As Inhibitors For Copper Corrosion: Down to the Molecular Scale

Abstract

The initiation of a corrosion process can be triggered by defects in the spatial distribution and molecular organization in the adsorbed layer of surfactant inhibitors. A detailed knowledge of the intermolecular forces between the inhibitor molecules and the interfacial bonding between the molecules and metal (oxide) surface will be decisive to unravel the mechanisms driving the initiation of corrosion and surface protection. In this work, adsorbed organic layers of two mercapto-based benzimidazole molecules, 5-methoxy-2-mercapto-benzimidazole (SH-BimH-5OMe) and 5-amino-2mercapto-benzimidazole (SH-BimH-5NH2) were studied regarding their inhibition performance of copper corrosion. Atomic force microscopy was used to address the stability and intermolecular forces of the self-assembled monolayers, using imaging and force measurement modes. For a film formed by amino derivative molecules, molecular fishing by a gold coated AFM tip frequently occurred. For molecular layers of the methoxy derivative, no fishing events were observed, indicating the formation of a constant functional performance layers. X-ray photoelectron spectroscopy revealed that SH-BimH-5OMe molecules form a stronger surface bond strength/interfacial bonding SAM layers on Cu surfaces as compared to SH-BimH-5NH2 molecules. Results of computational DFT modelling and electrochemical corrosion tests are in line with the AFM and XPS results.

Evolution and stability of 2-mercaptobenzimidazole inhibitor film upon Al alloy 6061

“…Moreover, instead of a mono layer, multiple layers of a complex inhibitor system have formed. The EDS results are consistent with the findings of EIS results regarding the presence of a thick protective/barrier layer that has delayed the ionic diffusion process and protected IMPs from corrosion attack [43].…”

“…Based on previous articles, the tentative mechanism revealed from the XPS etching results could be expected. It was reported that S could be firmly adsorbed to the substrate surface (S-Al) and masked the bulk from corrosion [43]. It has been reported that 2-MBI in thione form could be adsorbed on Au surface in a solution having pH > 2 with an upward geometry [28].…”

“…Heterocyclic organic compounds have been numerously reported for corrosion mitigation of Cu, Au, and Fe alloys. The adsorption mechanisms have been explained by the interaction of electron-rich ligands with bulk metal [39,[42][43][44]. Azole-based heterocyclics, especially 2-MBI, have attracted corrosion researchers' interest due to their rapid film-forming behaviour over Cu-rich IMPs of aerospacegrade AA2024 alloy [45][46][47][48].…”

Layered Inorganic–Organic 3,5-Dimethylpyrazole-4-Sulfonate Films for Protection of Copper Surfaces against Corrosion

“…2.12(2) 2.965( 7) 164 (7) x, y − 1, z O12B−H12D 2). Within the organic layer (Figure 5), the pyrazole moieties form a double layer.…”

“…Corrosion is further promoted by oxygen and chloride ions, commonly present in water. , Corrosion of metals in general is a considerable problem: in the U.S. alone, the annual direct cost of metallic corrosion is $276 billion, which represents over 3% of the gross domestic product (GDP) . Therefore, the improved protection of metallic copper surfaces against corrosion in aqueous media (e.g., heat exchanger components in cooling water systems, post chemical–mechanical polishing cleaning) is an important area of both fundamental and applied research. − …”