2-Mercaptobenzothiazole corrosion inhibitor deposited at ultra-low pressure on model copper surfaces

Abstract

Adsorption of 2-mercaptobenzothiazole (2-MBT) at ultra-low pressure and room temperature on metallic and pre-oxidized Cu(111) surfaces and its thermal stability were investigated using X-ray photoelectron spectroscopy in order to better understand the interfacial corrosion inhibiting properties. 2-MBT is lying flat in the monolayer with two sulphur atoms bonded to Cu and decomposes partially yielding atomic sulphur when interacting with metallic copper prior to forming molecular multilayers. Decomposition is prevented by surface pre-oxidation with 2D oxide dissociation accelerating the 2-MBT initial adsorption kinetics. 2-MBT further decomposes and partially desorbs above 100 • C. A pre-adsorbed 2-MBT monolayer on metallic copper inhibits surface corrosion. sulphur in the organic molecule could improve its capacity as corrosion inhibitor by forming coordinative bonds with copper [1]. It has been shown that 2-MBT dissolved in solution can react with copper to form a complex which acts as a protective layer at the copper surface [21]. However, controversy exists on the chemical nature of the complex formed, as well as on the fundamental mechanisms of the inhibiting interaction. The resulting structures of the protective layer formed on copper are also still not clear. Most notably, the exact role of the surface oxide in the inhibiting function remains to be studied. With few exceptions [12], experimental research concerning corrosion inhibitors have been done by immersion into solutions containing the organic compounds [7-24]. However, in order to elucidate the interaction mechanisms, deposition of the molecule evaporated in vacuum could be more insightful, since it allows controlling each step of the deposition process in a well-defined environment and on a well-defined surface. Data have been reported for vacuum evaporation [25, 26] of 1,4-benzenedimethanethiol (BDMT) on Au(111), Au(110), Cu(100) and Cu(111) single crystal surfaces. The authors found that on Cu (100) and Cu(111) surfaces, which are more reactive, BDMT dissociates in the initial stage of adsorption, resulting in atomic S adsorbed on the Cu surface. This phenomenon was not observed for the adsorption of benzotriazole on Cu(100) [27].In this work, the adsorption of 2-MBT at ultra-low pressure (ULP) and room temperature on clean and pre-oxidized Cu(111) surfaces and its effect on the oxidation of copper were investigated using ultra-high vacuum (UHV) spectroscopic techniques. The results were compared to those obtained for ULP deposition on the oxide-covered Cu(111) surface prepared in air. The thermal stability of the adsorbed molecular layer under UHV was also studied. This work brings new insight into the interaction of 2-MBT with copper, which allow us to better understand its corrosion inhibition mechanisms. Material and methodsA high purity (99.999%) Cu(111) single-crystal was used in this work. The surface was mechanically polished to 1/4 µm (diamond paste), successively rinsed with acetone, ethanol, and ultra pure (UP) water (resistivity > 18...

Moiré Structure of the 2-Mercaptobenzothiazole Corrosion Inhibitor Adsorbed on a (111)-Oriented Copper Surface

“…The S 2p spectrum shows that the growth of 2-MBT on the Moiré structure at room temperature gives rise to two other components, S 1 and S 2 , with 2p 3/2 peaks at 164.2 and 162.8 eV corresponding to the endocyclic and exocyclic S atoms in the 2-MBT molecule not bonded to copper, respectively. 22 , 24 This confirms the adsorption of molecules on the Moiré structure. The comparison of the intensity of the XPS spectra with those obtained from Cu(111) with the pre-adsorbed 2-MBT monolayer 22 confirmed the formation of one equivalent 2-MBT monolayer on the Moiré structure at room temperature.…”

“… 22 A N 1s component at 399.0 eV was observed, corresponding to N in the non-bonded molecule. 22 XPS spectra obtained from the 2-MBT monolayer formed on Cu(111) at room temperature are also shown for comparison. The intensity of the S 2p spectrum was found to be 0.6 times that obtained from the Moiré structure, and the intensity of the N 1s spectrum was found to be 1.3 times that obtained from the Moiré structure, suggesting that the Moiré structure is richer in S than the 2-MBT monolayer formed at room temperature.…”

“…The C 2 and C 3 components at binding energies of 285.8 ± 0.2 and 284.7 ± 0.1 eV correspond to C–N bond and the remaining C atoms in the benzene ring, respectively. 22 The intensity of C 3 is 5–6 times that of C 2 . This confirms the decomposition of 2-MBT by the cleavage of the C=S and C–S bonds.…”

“… XPS spectra of the S 2p, N 1s, and C 1s core levels for Cu(111) that was exposed to 45 L of 2-MBT at 150 °C (Moiré structure) and 15 L of 2-MBT at RT (2-MBT monolayer 22 ) for comparison. The S 2p spectrum for a R19.1° S/Cu(111) surface is also shown for comparison.…”

DFT-Based Cu(111)||Cu2O(111) Model for Copper Metal Covered by Ultrathin Copper Oxide: Structure, Electronic Properties, and Reactivity

“…Recently, the pre-adsorption of 2-mercaptobenzothiazole (MBT) and 2-mercaptobenzimidazole (MBI) corrosion inhibitors at ultra low pressure on Cu(111) has been shown to markedly retard the oxidation kinetics. [35][36][37] Preprint accepted for publication in J. Phys. Chem.…”