In Situ STM Study of Cu(111) Surface Structure and Corrosion in Pure and Benzotriazole-Containing Sulfuric Acid Solution

Abstract

We present results of an in situ STM study on the surface structure and anodic dissolution of Cu(111) electrodes in pure 0.01 M H2SO4 solution and in solution containing the corrosion inhibitor benzotriazole (BTAH), which is aimed at an atomistic understanding of the dissolution process and the inhibitior effects. The initial stages of Cu dissolution as well as the adsorption of BTAH are pronouncedly influenced by the presence of the ordered sulfate adlayer, which forms in the double layer potential regime and induces a reconstruction of the underlying Cu surface layer, together with a reorientation of the steps along the close-packed lattice directions. Cu dissolution in pure H2SO4 solution proceeds by a step flow mechanism. The onset of dissolution is critically affected by the relative orientation of the sulfate adlayer on the lower terrace side, with the stability being highest for steps running perpendicular to the close-packed sulfate rows. The retracting steps often expose apparently disordered areas, which are attributed to a disordered sulfate adlayer on a Cu surface where, because of kinetic limitations, a well-ordered reconstruction has not yet reformed. BTAH adsorption is only observed in the potential regime of the ordered sulfate adlayer. The BTAH adlayer is highly defective, which is attributed to the removal of the reconstruction due to sulfate adlayer displacement. Islands with poorly ordered 1D chain structures are surrounded by areas with no resolved structure. Cu dissolution inhibition is manifested by an anodic shift in the onset of dissolution as well as by the blocking of the step flow etch mechanism, reflecting a stabilization of the Cu steps by adsorbed BTAH. Dissolution at higher potentials proceeds predominantly via formation of monolayer etch pits. When the potential is reversed back into the double layer regime, smoothening of the surface is observed with a rate that increases strongly with decreasing potential.

A quartz crystal microbalance study of the kinetics of interaction of benzotriazole with copper

“…1, 2). There is strong evidence that the corrosion rate of copper in the presence of BTAH is negligibly small compared to that in its absence [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Had BTAH merely stopped the corrosion reaction, one would have observed a constant mass and constant frequency after addition of BTAH.…”

“…Benzotriazole (C 6 H 5 N 3 , BTAH) has been extensively studied as an inhibitor for the corrosion of copper and many of its alloys [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16], for dezincification of brass [17,18] and as additive in the etching [19], electrodeposition [20][21][22] and in the chemical mechanical polishing of copper [23][24][25]. It has also been reported to inhibit the corrosion of iron [26][27][28], cobalt [29], zinc [30], and nickel [28] and to enhance the resistance of tin bronze to oxidation in air [31].…”

In-situ Characterization of Metal/Electrolyte Interfaces: Sulfate Adsorption on Cu(111)

“…Such STM studies have e.g. led to the insight, that specifically adsorbed anions may strongly influence many dynamic processes like surface diffusion, step reorientation [5], initial stages of corrosion [6,7] or surface reconstruction [8] and, thereby, the surface morphology as a whole. In turn, the intensities and frequencies of in-situ Fourier Transform Infrared (FTIR) spectra provide additional information about total coverages as well as the vibrational and, hence, interaction properties of adsorbed, infrared active molecules.…”

Corrosion inhibition of copper in tetra‐n‐butylammonium bromide aqueous solution by benzotriazole

“…The remarkable efficiency of benzotriazole (BTA) as the corrosion inhibitor of copper has been well established for over 40 years in various solutions such as NaCl [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], NH 4 Cl [9,24], KCl [25,26], Na 2 B 4 O 7 [27], NaAc [28], K 2 SO 4 [29,30], HCl [9,31,32], H 2 SO 4 [9,[32][33][34][35][36][37], citric acid [38], and water [39]. The protective action of BTA has been attributed to the formation of a protective film of Cu(I) BTA or an adsorbed layer of BTA on the copper surface .…”