Investigating the effect of zinc on the behaviour of the copper corrosion inhibitor benzotriazole at a molecular scale

The interactions of the corrosion inhibitor benzotriazole (BTAH) with copper have been extensively studied, however consideration of the other elements in copper-based alloys is much sparser. With a view towards corrosion inhibition on brass, the interactions of BTAH with zinc containing surfaces under ultra-high vacuum conditions have been investigated in this paper, using scanning tunnelling microscopy and high-resolution electron energy loss spectroscopy. Density functional theory calculations were used to complement the experimental findings. Zinc-doped Au(1 1 1) surfaces were used to study Zn-BTAH species on a relatively inert substrate, and zinc-doped Cu(1 1 1) surfaces were used to study BTAH in an environment where both copper and zinc atoms are available. In the case of Zn/Au(1 1 1), several well-defined structures – including a kagome lattice – are formed, which are unlike any structures previously reported on copper and/or gold single crystal surfaces. The structures observed are dependent on both zinc surface coverage and annealing temperature. It is proposed that BTAH is deprotonated on the surface, and the observed structures are arrangements of Zn_x(BTA)_y species. In the case of Zn/Cu(1 1 1), a similar kagome lattice was observed, indicating that in the presence of both zinc and copper species, BTAH preferentially coordinates with zinc atoms.