Passivation of Copper: Benzotriazole Films on Cu(111)

Abstract

Benzotriazole (BTAH) has been used as a copper corrosion inhibitor since the 1950s. However, the molecular level detail of how adsorption and surface passivation occur remains a matter of debate. BTAH adsorption on a Cu(111) single crystal has been investigated from medium coverage to multilayer using scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), high resolution electron energy loss (HREEL) spectroscopy and supporting density functional theory (DFT) calculations. Both physisorbed and chemisorbed phases are observed. One extended and highly ordered self-assembled metal−organic phase is seen at saturation coverage and above. A metastable phase is also observed. Complete desorption occurs at ca. 600 K. Those structures are critically discussed in the light of some of the various adsorption models reported in the literature and an alternative adsorption model is proposed. These results allow a further understanding of the interaction between benzotriazole and copper and, in turn, may help understanding the mechanism for protection of copper and copper alloys from corrosion, substantially contributing to a long-standing debate.

The roles of mercapto, benzene, and methyl groups in the corrosion inhibition of imidazoles on copper: II. Inhibitor–copper bonding

“…Such scenario was recently demonstrated for benzotriazole on copper surfaces [12]; the respective activation barrier for the N-H bond cleavage was calculated to be 1.14 eV on Cu(111) [12], which is significantly larger than the current E * values of thiones, and yet the dissociation was found plausible on more open surfaces and low-coordinated defects [12]. It was also observed experimentally that the H1 atom of benzotriazole is removed upon chemisorption on copper surfaces, including the Cu(111), even under ultra-high-vacuum conditions [23,46,[79][80][81]. On this basis, we can reasonably conclude that the current-mercapto molecules should exist in dehydrogenated (deprotonated) thiolate form on Cu(111).…”

“…(ii) The interaction of corrosion inhibitor molecules with the adatom defects can be regarded as a first step toward the formation of organometallic complexes. A well known example is the benzotriazole-copper complex [9,11,20,23,[38][39][40][41][42][43][44][45][46]. Another prominent example is the alkanethiol self-assembled-monolayers on gold, where two alkylthiolate molecules bond with the Au adatom [47][48][49].…”

Structure and Reactivity of Cu-doped Au(111) Surfaces

“…6(e), black spectrum] [63]. On Cu(111) [64,65] BTAH forms essentially densely packed layers comprised of BTA-Cu-BTA dimeric and CuBTA monomeric species, as shown by STM [ Fig. 6(b); a model of the motif's basic unit is shown in the inset], chemisorbing in an almost upright configuration, with the triazole end toward the surface, as revealed by the decrease in intensity of the δ(C-H) mode, the presence of extra vibrations in the 100-200 meV range and the appearance of a strong ν(C-H) mode at ca.…”

“…400 K, whereas the chemisorbed dimer desorbs at ca. 595 K [65]. On Cu(110) flat-lying molecules in a (4×4) configuration [66,67] are seen to coexist with the upright dimer [67].…”

Ab initio modeling of the bonding of benzotriazole corrosion inhibitor to reduced and oxidized copper surfaces

“…[5][6][7][8]23,[25][26][27][28] The main findings of these studies are briefly explained below (section 3.1 and, in part, also 3.2) as to make a proper context for the current discussion paper.…”