Adsorbed corrosion inhibitors studied by electron spectroscopy: Benzotriazole on copper and copper alloys

Surface films formed by adsorption of benzotriazole (BTA), on copper and copper alloys have been studied by X-ray photo-electron spectroscopy (XPS). It is found that on both copper and copper-nickel alloys, benzotriazole forms a Cu(I)BTA surface complex. For the copper-nickel alloys the time taken to form the Cu(I)BTA film is dependent on the alloy composition. The Cu(I)BTA films were found to oxidize rapidly to a Cu(II) species on removal from the liquid phase. Surface films formed by BTA on 70 Cu : 30 Zn alloy were found to contain both copper and zinc, the copper again being in the Cu(I) state.A study of the adsorption of BTA on cathodically reduced copper surfaces strongly supports previous suggestions that the presence of Cu₃O facilitates formation of the surface film.     

The effect of various halide ions on the passivity of Cu, Zn and Cu-xZn alloys in borate buffer

Cu and Zn metals and four of their alloys, Cu-10Zn, Cu-20Zn, Cu-30Zn and Cu-40Zn, were studied in borate buffer, pH = 9.2, in the presence of the halides, NaF, NaCl, NaBr and NaI. Electrochemical polarization and SEM/EDS methods were used in the study. The mechanism of corrosion of copper and copper alloys induced by iodide ions differed fundamentally from that induced by other halide ions. Iodide ions promote the general type of corrosion during which very slowly soluble CuI is formed. F⁻, Cl⁻ and Br⁻ ions promote localized corrosion attack. All halide ions induce localized corrosion on the passive layer on zinc. The breakdown potentials of Cu, Zn and four Cu-xZn alloys were measured as a function of concentration and type of halide ions.     

Kinetics of corrosion inhibition of benzotriazole to copper in 3.5% NaCl

The kinetics of interaction of benzotriazole (BTAH) with the surface of copper were studied using an electrochemical quartz crystal microbalance (EQMB) and electrochemical impedance spectroscopy (EIS). Upon injecting BTAH into the electrolyte, three regions appear in the time response of the microbalance. Region I (at short time scale of few minutes) exhibits rapid linear growth of mass with time. This is attributed to the formation of a Cu(I)BTA film that is several hundred layers thick. Region II reveals adsorption of BTAH at a slower rate, on the inner Cu(I)BTA complex. Region III is a plateau indicating that the BTAH film attains an equilibrium thickness, which increases with the concentration of BTAH. The polarization resistance of the interface changes with time in a similar fashion while the double layer capacitance decreases. The results suggest that the thickness of the physically adsorbed film of BTAH increases with time and BTAH concentration while the thickness of the inner Cu(I)BTA remains constant. Two semicircles were obtained in the impedance spectra corresponding to the complex Cu(I)BTA and the physically adsorbed BTAH.     

The characterisation of the protective film formed by benzotriazole on the 90/10 copper-nickel alloy surface in H2SO4 media

The nature of the protective film formed by benzotriazole (BTAH) on the surface of the 90/10 CuNi alloy in deaerated 0.5 mol L⁻¹ H₂SO₄ solution containing Fe(III) ions as oxidant was investigated by weight-loss, calorimetric measurements, and by surface-enhanced Raman spectroscopy (SERS). The SERS measurements show that the protective film is composed by the [Cu(I)BTA]_n polymeric complex and that the BTAH molecules are also adsorbed on the electrode surface. A modification of the BET isotherm for adsorption of gases in solids is proposed to describe the experimental results obtained from weight-loss experiments that suggest an adsorption in multilayers. Electrochemical studies of copper and nickel in 0.5 mol L⁻¹ H₂SO₄ in presence and absence of BTAH have also been made as an aid to interpret the results. The calculated adsorption free energy of the cuprous benzotriazolate on the surface of the alloy is in accordance with the value for pure copper.     

The air oxidation of two-phase Cu-Ag alloys at 650–750°C

The corrosion of three two phase Cu-Ag alloys containing 25, 50, and 75 wt% Ag has been studied at 650 and 750°C. In all cases the alloys formed external scales of copper oxides. At the same time, an internal precipitation of Cu₂O within a silver matrix was also produced, with an oxide volume fraction larger for the alloys richer in Cu. Beneath this mixed layer a region of single-phase solid solution of Cu in silver formed for Cu-50Ag and especially for Cu-75Ag. Silver metal remained in the metal-consumption zone, acting essentially as an inert marker, except for a few particles with were incorporated into the growing scales. Both pure Cu and the alloys corroded parabolically, but the rate constants for the alloys decreased with increased Ag content under constant temperature. The various aspects of the corrosion of these alloys are examined by taking into account the possible effects associated with the presence of two metal phases.     

Some chemical aspects of the corrosion inhibition of copper by benztriazole

Measurements of the adsorption isotherm of benztriazole (BTA) on copper reveal that the inhibitor molecule is weakly held on the oxide covered surface until a critical solution concentration of BTA is reached above which good corrosion inhibition results. Consideration of the chemical equilibria between the oxides of copper and the dissociation of the BTA molecule in solution, show that this concentration corresponds closely to that at which the Cu(I)BTA complex is precipitated. The chemical nature of the complexes formed has been found by X-ray photo-electron spectroscopy to correspond closely to Cu(I)BTA for cuprous oxide-covered surfaces but is of a more complicated nature for cupric oxide-covered surfaces, although both seem to be equally effective in preventing the corrosion of copper. No tendency for the Cu(I) complex to oxidize to the Cu(II) state over short times was found. Polarization studies of the inhibition process suggest that the surface is largely covered by the complex; impedance measurements imply a double layer at the surface which forms sequentially with time.     

Cu-Ni合金BTA复配体系钝化处理工艺研究

采用苯并三氮唑(BTA)复配钝化体系对B10 Cu-Ni合金进行钝化处理,以提高其在含硫化物环境介质中的耐腐蚀性能,并研究工艺参数对钝化膜耐蚀性的影响规律.利用动电位极化曲线和电化学阻抗谱研究钝化膜的耐腐蚀性能,采用X射线光电子能谱分析钝化膜的化学成分.实验结果表明,在BTA与磺基水杨酸组成的复配体系中形成的钝化膜比BTA单一体系中形成的钝化膜具有更高的耐蚀性,这是磺基水杨酸与基体合金反应形成的络合物膜与Cu(I)BTA膜协同作用的结果;钝化处理的时间和温度是影响钝化膜耐蚀性的重要工艺参数,延长钝化时间和提高钝化温度均可以提高钝化膜的耐蚀性,60℃高温条件下5 min的钝化处理即能够达到常温条件下3 h的钝化处理效果.     

BTA系列Cu缓蚀剂的电化学行为

采用交流阻抗法和恒电位阶跃法研究了在硼砂缓冲溶 液（pH9.2）中BTA及其系列衍生物CBTME,CBTBE对Cu电极的缓蚀行为.结果表明：BTA对Cu 的缓蚀作用是由于在Cu表面上生成了Cu/Cu2O/Cu(I)BTA膜,阻滞了Cu的腐蚀,而且缓蚀剂 的浓度越高,生成的Cu/Cu2O/Cu(I)BTA膜越致密,抑制作用越强.含CBTME缓蚀剂的溶液 中,缓蚀效果随缓蚀剂浓度的升高而增强,但同浓度比较时,BTA的缓蚀效果优于CBTME.当 溶液中含有较低浓度CBTBE时,缓蚀剂促进Cu的腐蚀;而当溶液中含有较高浓度CBTBE时,缓 蚀剂才抑制Cu的腐蚀.一定比例的BTA和CBTME复配后对Cu的缓蚀作用有协同效应.以5 mg/L 为缓蚀剂总量,其最佳复配方案为2 mg/L BTA+3 mg/L CBTME.恒电位阶跃法测得的结果与 交流阻抗方法测得的结果相符.     

Copper corrosion mitigation by binary inhibitor compositions of potassium sorbate and benzotriazole

This work presents the combined effect of two inhibitors, potassium sorbate (2,4-hexadienoic acid potassium salt) and 1,2,3-benzotriazole, on the corrosion behavior of copper in sulfate based solutions. Individual and combined characteristics of copper corrosion inhibition in sulfate solution in the presence of potassium sorbate (K-sorbate) and benzotriazole (BTAH) were studied with the use of electrochemical, microscopic and spectroscopic methods. Whereas, BTAH alone protects copper from corrosion attack in sulfate solutions only in a limited potential range below 0.4 V vs. saturated calomel electrode (SCE), the presence of K-sorbate combined with BTAH in such solutions enables the protection of the copper surface at potentials above 0.4 V_SCE. The mixture of both inhibitors provides supplementary and robust corrosion protection of Cu over a wide potential range.     

Free-Cyanide Synthesis and Characterization of Cu–Zn Alloy by an Electrodeposition-Annealing Route

Substitution of cyanide in electroplating is a current challenge. We present an alternative method aiming to reduce the toxicity and the cost of electroplating of Cu–Zn alloy (usually prepared from cyanide baths) while maintaining the decorative qualities and anticorrosive properties of the coating. For this purpose, Cu–Zn alloys were obtained in two steps from non-cyanide electrolytes. First, a copper layer electrodeposited onto a nickel under-layer, followed by a thin layer of zinc from three different simple non-cyanide zinc baths. The Zn/Cu/Ni sandwich system was then subjected to heat treatment at a temperature of 400°C, to ensure the diffusion of zinc into the copper layer to give the desired Cu–Zn alloy structure. The synthesized films were characterized by using X-ray diffraction XRD, scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS). XRD demonstrated that the electrodeposited films are crystalline and present the Cu_0.7Zn_0.3 phase with preferential (111) orientation. An analysis of XRD patterns revealed that after heat treatment, the Cu–Zn alloys were composed of a predominating α-phase structure. The morphology and composition of the coatings depends on the zinc plating bath type. After annealing, well defined pseudospherical Cu–Zn grains were formed covering the entire substrate surface. The EDS analysis indicated the formation of Cu_0.7Zn_0.3 brass alloys. The results showed the feasibility of this low-cost new route for the preparation of good quality Cu–Zn alloys from cyanide-free electrolytes.     

Corrosion inhibition of copper–phosphorus brazing alloys in tetra‐n‐butylammonium bromide aerated aqueous solution by benzotriazole

The corrosion inhibition behavior of benzotriazole (BTA) on a brazing alloy, CuP in the non‐welded and welded conditions in 17 wt% (0.534 mol/L) tetra‐n‐butylammonium bromide (TBAB) aerated aqueous solution was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy/energy dispersive X‐ray spectroscopy techniques. The experimental results showed that BTA could protect effectively copper alloys in aqueous TBAB solution. The inhibition efficiency of BTA increased with increasing inhibitor concentration from 0.1 to 6 g/L, attaining efficiencies of up to 96% calculated according to different methodologies. Corrosion current densities were lower after the melting process. Galvanic studies showed that copper behaved as the anode when coupled to its alloys. The addition of BTA caused an increase in charge transfer resistance and a decrease in the capacitance of the double layer. Adsorption of BTA in 17 wt% TBAB solution on the copper alloys' surface was found to obey the Langmuir adsorption isotherm.     

苯并三唑对碳钢/铜合金电偶腐蚀行为的影响

目的 研究NaCl溶液中苯并三唑(BTA)对碳钢/铜合金电偶腐蚀行为的影响.方法 使用丝束电极(WBE)技术和电化学阻抗谱(EIS)技术研究在未添加和添加BTA的NaCl溶液中,丝束电极表面的电位分布、电流密度分布和电化学阻抗谱演化,同时对比分析碳钢区域与铜合金区域的阻抗谱特征.结果 在未添加BTA的条件下浸泡72 h...     

Effects of Niobium Ammonium Oxalate and Benzotriazole on the Corrosion Resistance of Zinc Phosphate Layer

In this study, the viability of nickel replacement in zinc phosphate baths by niobium ammonium oxalate (Ox) and benzotriazole (BTAH) was studied. Samples of carbon steel (SAE 1010) were phosphated in two zinc phosphate baths, one containing nickel (PZn+Ni) and another containing Ox and BTAH (PZn+Ox+BTAH). The corrosion resistance of the phosphated samples was analyzed in a NaCl 0.5 mol/L solution using open circuit potential measurements, anodic and cathodic polarization curves, and electrochemical impedance spectroscopy. Surface analysis was carried out by scanning electron microscopy and energy dispersive spectroscopy. The results showed that the PZn+Ni layer presented a needle-like morphology and that the crystals of PZn+Ox+BTAH showed granular morphology. The electrochemical results showed that the highest corrosion resistance was associated to the PZn+Ox+BTAH layer.     

Development of novel brasses to resist dezincification

The effect of alloying Sn, Pb, As, Sb and P on the dezincification of commercial brass 60Cu-39Zn-1Pb has been investigated in 1% CuCl₂ solution by immersion studies and electrochemical measurements. Specimens with a smooth surface finish exhibited more resistance to dezincification. Appreciable inhibitive effect on dezincification was observed for the 55Cu-40Zn-3Pb-2Sn brass composition. The galvanic coupling of lead phase with the matrix accelerated corrosion. To improve the dezincification resistance of the Sn containing brass, As, Sb and P were added at two different levels (0.05% and 0.1%). Brass of composition 48.95Cu-45Zn-5Pb-1Sn-0.05As was more resistant indicating the synergistic effect of Sn and As. The effect of 0.05 and 0.1% of arsenic addition with various concentrations of zinc was also studied. The alloy of composition 57.90Cu-40Zn-2Pb-0.1As showed better corrosion resistance than the alloy containing 1% Sn and 0.05% As (48.95Cu-45Zn-5Pb-1Sn-0.05As). To understand the influence of Sn and As on the dezincification of commercial brass, linear polarization and cyclic voltammetry experiments were conducted for the alloys 60Cu-39Zn-1Pb, 55Cu-40Zn-3Pb-2Sn and 57.90Cu-40Zn-2Pb-0.1As. Linear polarization measurements indicated that the alloys 55Cu-40Zn-3Pb-2Sn and 57.90Cu-40Zn-2Pb-0.1As possessed higher resistance to corrosion than commercial brass. Inspection of cyclic voltammograms revealed that the peak current densities as well as the passive current density were lower for the alloys 55Cu-40Zn-3Pb-2Sn and 57.90Cu-40Zn-2Pb-0.1As than the alloy 60Cu-39Zn-1Pb. The surface layer on the alloys 60Cu-39Zn-1Pb, 55Cu-40Zn-3Pb-2Sn and 57.90Cu-40Zn-2Pb-0.1As after immersion of 72 h in 1% CuCl₂ solution were analyzed by X-ray diffraction and scanning electron microscopy. Higher enrichment of Sn and As at the interface of surface layer and metal was indicated for the alloys 55Cu-40Zn-3Pb-2Sn and 57.90Cu-40Zn-2Pb-0.1As, respectively.     

Inhibition of copper corrosion by 1,2,3-benzotriazole: A review

Benzotriazole (BTAH) has been known for more than sixty years to be a very effective inhibitor of corrosion for copper and its alloys. In spite of numerous studies devoted to the investigation of BTAH action, the mechanism of its action is still not completely understood. The aim of this review is to summarize important work in the field of BTAH as a copper corrosion inhibitor, from the early discoveries to the present time. Special attention is given to the BTAH surface structure. The disagreement between findings and mechanisms is discussed.     

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

The corrosion inhibition behavior of benzotriazole (BTA) on copper in 17 wt% tetra‐n‐butylammonium bromide (TBAB) aerated aqueous solution was investigated by weight‐loss tests, potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscopy/energy dispersive X‐ray spectroscopy. BTA is a good inhibitor in 17 wt% TBAB solution. The inhibition efficiency of BTA increases with increasing inhibitor concentration, attaining efficiencies of up to 90% calculated according to different methodologies. Adsorption of BTA in 17 wt% TBAB solution on the copper surface was found to obey the Langmuir adsorption isotherm.     

Synergistic effect of CeCl3 and benzotriazole on corrosion resistance of naturally aged and artificially aged AA2024 aluminium alloy

The corrosion behaviours of naturally aged and artificially aged AA2024 aluminium alloys in 0.5 mol/dm³ NaCl solution in the presence of environmentally friendly corrosion inhibitors of 10 mmol/dm³ CeCl₃, 10 mmol/dm³ BTA and the inhibitor mixture (5 mmol/dm³ CeCl₃ + 5 mmol/dm³ BTA) were analyzed. The goal of this work was to determine the level of the synergistic effect of the inhibitor mixture and to explain the nature of this effect. Corrosion properties of the inhibitor layer were studied using the electrochemical impedance spectroscopy (EIS), while the resistance to pit formation and pit growth was studied by applying potentiodynamic polarisation tests. The results of scanning electron microscopy (SEM/EDS) showed that the size of pits formed in naturally aged aluminium alloy was smaller than that formed in artificially aged alloy. The synergistic effect of the inhibitor mixture on corrosion properties of naturally aged alloy was observed throughout 96 h, and in later phases of testing of artificially aged alloy. The synergistic effect of the inhibitor mixture was not noticed on pit formation and pit growth.     

低压冷喷涂Cu-Zn复合涂层耐蚀性能的研究

本文使用低压冷喷涂技术,分别在45#钢基体与45#钢加镀铬层基体上制备铜锌涂层试样。通过静态浸泡与铜加速醋酸盐雾腐蚀试验（CASS）对涂层和涂层加镀铬层试样的腐蚀性能进行研究;采用SEM、XPS对腐蚀前后涂层与镀铬层的微观形貌与元素进行表征。结果表明：静态腐蚀过程中,铜锌涂层的耐腐蚀性优于铜锌涂层加镀铬层;CASS实验中,随着原始粉体中锌含量的增加,涂层试样与涂层加镀铬层试样的耐腐蚀性能提高,当铜锌比为6:4时,对应涂层试样、涂层加镀铬层试样与纯镀铬层的耐腐性能达到六级。铜锌涂层在腐蚀液中由于电化学腐蚀及氯化作用,导致铜锌均发生了腐蚀,其腐蚀产物主要为Zn(OH)2、Cu2O与CuCl2。铜锌涂层加镀铬层试样在腐蚀过程中,锌的腐蚀在一定成上可以起到减缓镀铬层腐蚀的作用,这种减缓的作用与镀铬层上析出的铜膜共同保护镀铬层,增强其耐腐蚀性能。     

Die Abhängigkeit der Spannungskorrosionsanfälligkeit vom Werkstoffzustand bei homogenen Kupfer-Zink-Legierungen

Interdependence of stress corrosion susceptibility and structural state of homogeneous copper-zinc alloys Experimental investigations in ammoniacal solution of copper and ammonium sulfates have shown, that — with equal load ratio (σ/σ_0,2 = 0,9) — CuZn alloys are less sensitive to stress corrosion cracking after recrystallizing annealing than after cold working. The sensitivity increases with increasing Zn content and appears to depend primarily from the dislocation structure: parallel structures are highly sensitive while increasing transition to cellular dislocation structure reduces stress corrosion susceptibility. In the cold worked alloy the crack geometry is predominantly transcrystalline, in the recrystallized state intercrystalline. Similar relations between dislocation structure and susceptibility seem to exist in the case of austenitic stainless steels.     

Corrosion study of copper in the presence of benzotriazole and its hydroxy derivative

The inhibitory properties of benzotriazole (BTAH) and its hydroxy derivative, 1‐hydroxy‐benzotriazole (BTAOH) on copper corrosion, were compared in 3% NaCl solution using cyclic voltammetry (CV), immersion tests, profilometry and scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDX). CV experiments showed rapid interaction of both inhibitors with a Cu surface, but only at high concentrations. Immersion tests under stationary conditions showed that BTAOH offered corrosion protection only at concentration of 10 mM. Moreover, it was not effective under stirring conditions at any of the concentrations investigated. In contrast, BTAH exhibited good corrosion inhibition ability in all immersion tests. BTAOH, at up to 1 mM, increased the surface roughness of Cu more than 3% NaCl solution alone, but a significant reduction of surface roughening was observed when BTAH was present. Porous cross‐linked acicular structures and star‐like structures were observed using SEM/EDX in the case of BTAOH treatment. When Cu was treated with BTAH, roundish surface structures composed of bent plates with toothed‐like edges, acicular structures and non‐porous few hundred nm thick plates were observed.