Inhibition of Copper Corrosion

Between 1985 and 1987, Fleischmann et al. [21-23] continued to perform SERS experiments that led to corrosion rates which could be compared with conventional electrochemical corrosion rate (4oi.) measurements. The results of these studies provided a dynamic description of the Cu/electrolyte interface, as a function of potential. 

Fleischmann et al [22] compared benzotriazole and 2-mercaptobenzoxazole as inhibitors of copper corrosion in KCl solutions containing low concentrations of cyanide. Benzotriazole proved to be an ineffective inhibitor in cyanide media, while 2-mercaptobenzoxazole remained effective. SERS showed that cyanide, revealed by a broad band centred at 2090 cm displaced benzotriazole from the Cu surface, whereas 2-mercaptobenzoxazole displaced adsorbed cyanide. A synergetic inhibition of Cu corrosion by benzotriazole and benzylamine, both in chloride and chloride/cyanide media, was also shown [22]. As SERS showed that benzylamine had not been adsorbed, its beneficial effect was ascribed to an improved film formation. Subsequent 4or measurements showed that benzotriazole, MBO, 2-mercaptobenzothiazole and 2-mercaptobenzimidazole were all effective inhibitors of copper corrosion in neutral chloride solutions, but the inhibition efficiency of benzotriazole was decreased at pH 1-2 [23]. SERS spectra showed that, at pH 7, benzotriazole and its anionic form were coadsorbed and Cl was excluded from the interface. However, at pH 2 undissociated benzotriazole and CH were coadsorbed, such that Cu underwent corrosion. In contrast, the anion from 2-mercaptobenzothiazole was the only adsorbed species at pH between 7 and 2 only at pH 1 was the neutral 2-mercaptobenzothiazole molecule detected. Competitive adsorption experiments showed that the inhibitive action of benzotriazole and 2-mercaptobenzothiazole in neutral/acid media could be explained in terms of adsorption strength. 

In 1990, Fleischmann et al. used NIR Fourier transform SERS (NIR FT-SERS) [71] to study the Cu corrosion inhibitors, benzotriazole and tolyltriazole. Diagnostic bands were identified for each compound, whereby benzotriazole and tolyltriazole were coadsorbed and found to displace each other, depending on their relative concentrations. The NIR FT-SERS investigations were extended to an antifreeze (ethylene glycol) mixture [24], in which both benzotriazole and tolyltriazole were identified by SERS as being adsorbed 

The Cu/ benzotriazole system was revisited by Chan and Weaver [72], who explored a wide pH range (2 to 13) using both HjO and DjO as solvent. It was shown that, at pH 2 and E -0.3 V (vs SCE), benzotriazole in both H and D forms were adsorbed through then-azole ring, with two N atoms interacting with Cu. At about E = -0.2 V, the spectra of both forms became identical due to formation of the copper(I) complexes with the deprotonated benzotriazole, [Cu(I)BTA] . It was also shown that adsorbed benzotriazole was converted to [Cu(I)BTA] upon exposure to air. 

During recent years, SERS spectra have been used to acquire basic information on new inhibitors [74-77], and also on the adsorption mode of benzotriazole in new solvent environments such as ionic liquids [78]. Thus, three decades after the pioneering studies [19-21], SERS spectroscopy is becoming a standard technique in studies of Cu corrosion inhibition. 

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Inhibitors form a film on the surface that blocks the dissolution of the substrate. Adsorption of an alkyl-thiol to the surface of the CU3AU alloy resulted in an inaeased surface tension of the gold film this is observed as an increase in the value of <., which depresses dissolution of copper. This behavior resembles inhibition of copper corrosion on a pure copper surface where benzotriazole increases the potential to start significant copper dissolution this was demonstrated by Cruickshank et using in situ AFM. However, when the critical potential for benzotriazole film... 

Inhibition of Copper Corrosion by Azole Compounds in Acidic Aqueous Solutions... 

Aramaki K, Kiuchi T, Sumiyoshi T, Nishihara H. Surface enhanced Raman scattering and impedance studies on the inhibition of copper corrosion in sulphate solutions by 5-substituted benzotriazoles. Corr Sci 1991 32(5-6) 593. 

Zhang D-Q, Gao L-X, Cai Q-R, Lee KY (2010) Inhibition of copper corrosion by modifying cysteine self-assembled film with alkylamine/alkylacid compounds. Mat Corros 61 16-21... 

N. Souissi, E. Triki, A chemiometric approach for phosphate inhibition of copper corrosion in aqueous media, J. Mater. Sci. 42 (2007) 3259—3265. 

M.M. Singh, R.B. Rastogi, B.N. Upadhyay, Inhibition of copper corrosion in aqueous sodium chloride solution by various forms of the piperidine moiety. Corrosion 50 (1994) 620-625. 

Milosev et al. performed a series of experimental and theoretical studies on the azoles inhibition properties for Cu [27, 34, 74, 75, 89-92]. The inhibition of copper corrosion in 3% NaCl solution was studied by using a well-known inhibitor, benzotriazole (BTAH) and its derivative 1-hydroxybenzotriazole (BTAOH) [74]. Corrosion parameters and inhibition effeetiveness were determined experimentally. It was shown that benzotriazole is a more effective inhibitor of the corrosion of copper in chloride media than is 1-hydroxybenzotriazole. 

Blajiev, O. and A. Hubin, Inhibition of copper corrosion in chloride solutions by amino-mercapto-thiadiazol and methyl-mercapto-thiadiazol An impedance spectroscopy and a quantum-chemical investigation. Electrochimica Acta, 2004. 49(17-18) p. 2761-2770. 

Finsgar, M., I. Milosev, and B. Pihlar, Inhibition of copper corrosion studied by electrochemical and EQCN techniques. Acta Chimica Slovenica, 2007. 54(3) p. 591—597. 

Liao, Q.Q-. Yue, Z.W., Yang, D. et al. (2011) Inhibition of copper corrosion in sodium chloride solution by the self-assembled monolayer of sodium diethyldithiocarbamate. Corrosion Science, 53,1999-2005. 

Little work has been carried out on the mechanism of inhibition of the corrosion. of copper in neutral solutions by anions. Inhibition occurs in solutions containing chromate , benzoate or nitrite ions. Chloride ions and sulphide ions act aggressively. There is evidence that chloride ions can be taken up into the cuprous oxide film on copper to replace oxide ions and create cuprous ion vacancies which permit easier diffusion of cuprous ions through the film, thus increasing the corrosion rate. 

Corrosion inhibitor - corrosion inhibitors are chemicals which are added to the electrolyte or a gas phase (gas phase inhibitors) which slow down the - kinetics of the corrosion process. Both partial reactions of the corrosion process may be inhibited, the anodic metal dissolution and/or the cathodic reduction of a redox-system [i]. In many cases organic chemicals or compounds after their reaction in solution are adsorbed at the metal surface and block the reactive centers. They may also form layers with metal cations, thus growing a protective film at the surface like anodic oxide films in case of passivity. Benzo-triazole is an example for the inhibition of copper cor-... 

Fox PG, Lewis G, Boden PJ. Some chemical aspects of the corrosion inhibition of copper by benztriazole. Corrosion Sci 1979 19 457. 

Szocs E, Vastag GY, Shaban A, Konczos G, Kalman E. Investigation of copper corrosion inhibition by STM and EQCM techniques. J App ElectroChem 1999 29 1339. 

Fleischmann M, Mengoli G, Musiani MM, Pagura C (1985) An electrochemical and Raman spectroscopic investigation of synergetic effects in the corrosion inhibition of copper. Electrochim Acta 30 1591-1602... 

Inhibition of general corrosion by biofilms has been reported for mild steel, copper, aluminum and stainless steels, and brass. The mechanisms most frequently cited for the inhibition are formation of a diffusion barrier to corrosion products that stifles metal dissolution, consumption of oxygen by respiring aerobic microorganisms within the biofilm causing a diminution of that reactant at the metal surface, production of metabolic products that act as corrosion inhibitors (e.g., siderophores) or specific antibiotics that prevent proliferation... 

K.H. Gob, T.T. Lim, P.C. Chui, Evaluation of the effect of dosage, pH and contact time on high-dose phosphate inhibition for copper corrosion control using response surface methodology (RSM), Corros. Sci. 50 (2008) 918-927. 

Some of the types of compounds that function through electrostatic adsorption may also function by chemisorption. Chemisorption is most evident with nitrogen or sulfur heterocyclics. Benzotriazole and polytriazole, both effective inhibitors of copper corrosion, are believed to operate through chemisorption, as does 0. IM butylamine, which is effective in inhibiting the corrosion of iron in concentrated perchloric acid. However, the effectiveness of a given compound depends on the mechanism and operating conditions. 

Three corrosion inhibitors for copper, 3-amino-l,2,4-triazole (ATA), benzotriazole (BTAH), and 1-hydroxybenzotiiazole (BTAOH), were investigated by corrosion experiments and atomistic computer simulations [75]. The trend of copper corrosion inhibition effectiveness of the three inhibitors in near-neutral chloride solution was determined experimentally as BTAH > ATA > BTAOH. An exhaustive analysis of the possible interactions between the molecules (in their neutral or deprotonated form) and the surface was done with PBE-D [75]. Physisorption, chemisorption, self-assembly as well as organome-tallic polymer formation attheCu(lll) surface were considered. The results are reported in Table 5.4. 

Scendo M, Uznanska J (2011) The effect of ionic liquids on the corrosion inhibition of copper in acidic chloride solutions. Int J Corros. doi I0.II55/20II/7I8626... 

Fleischmann, M., Hill, I.R., Mengoli, G. and Musiani, M.M. (1983) The synergetic effect of benzylamine on the corrosion inhibition of copper by benzotriazole. Electrochimica Acta, 28, 1325. 

Fleisehmann, M., MengoU, G., Musiani, M.M. and Pagura, C. (1985) An eleetrochemical and Raman speetroseopie investigation of synergetie effeets in the corrosion inhibition of copper. Electrochimica Acta, 30,1591. 

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