Time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy study of 2-phenylimidazole on brass

Abstract

Rationale: This work presents the first surface analysis investigation of 2-phenylimidazole (PhI) as a corrosion inhibitor for brass in a 3 wt.% NaCl solution using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS).

Methods: A time-of-flight secondary ion mass spectrometer was used to describe the elemental and molecular specific signals on the brass surface. Gas cluster/monoatomic ion beam depth profiling and two-dimensional (2D) imaging showed the surface properties of the PhI surface layer. In addition, detailed XPS was used to describe the element-specific signals on the brass surface. Furthermore, principal component analysis demonstrated the distribution of the different phases of the surface. Finally, the applicability of PhI in hot corrosion studies was suggested by a thermal stability experiment.

Results: TOF-SIMS measurements showed an intense positive-ion TOF-SIMS signal for protonated PhI, i.e. C₉ H₉ N₂ ⁺ at m/z 145.07. Moreover, there was an intense negative-ion TOF-SIMS signal for deprotonated PhI, i.e. C₉ H₇ N₂ ¯ at m/z 143.06. Gas cluster ion beam sputtering associated with the analysis of the XPS-excited Cu L₃ M_4,5 M_4,5 revealed a connection between Cu(I) and PhI to form organometallic complexes.

Conclusions: The formation of the organometallic complexes with Cu and Zn metal atoms/ions was identified using TOF-SIMS in positive and negative polarity mode: PhI-Cu, PhI-Cu₂ , PhI-Zn, and PhI-Zn₂ complexes were present on the brass surface. The TOF-SIMS measurements were supported by XPS measurements.