Synthesis of New Benzotriazole Derivatives Containing Carbon

Article pubs.acs.org/IECR

Synthesis of New Benzotriazole Derivatives Containing Carbon Chains as the Corrosion Inhibitors for Copper in Sodium Chloride Solution Yulong Gong, Zhenqiang Wang, Fang Gao,* Shengtao Zhang,* and Hongru Li* College of Chemistry and Chemical Engineering, Chongqing University, Chongqing, 400044, China S Supporting Information *

ABSTRACT: In this study, a series of benzotriazole derivatives with various carbon chains (n = 1, 3, 4, 6, 7, 9, 10, 12, 16) were synthesized for the corrosion inhibition of copper in 3.5 wt % (wt %) NaCl solution. The corrosion inhibition efficiencies of these inhibitors in 3.5 wt % NaCl solution for copper were measured by various measurements including the polarization curves, the electrochemical impendence spectroscopy as well as the weight loss method. The inhibition mechanism of these new target molecules were analyzed by the plots of Tafel, Nyquist, and Bode. The corrosion inhibition effect was also evaluated by scanning the copper surface with an electron microscope. The results show that the corrosion of copper in chloride aqueous solution is efficiently inhibited by these new organic inhibitors. Furthermore, the corrosion inhibition efficiencies of the target inhibitors are shown to have much dependence on the carbon chain length attached to the molecular backbone. The inhibitor carrying a 7carbon chain displays the greatest inhibition efficiency as large as ∼98% at 0.15 mM, while even the poorest inhibitor containing a 2-carbon chain shows ∼60% inhibition efficiency. The adsorption of these new inhibitors on copper was further revealed by analysis of Langmuir isotherms and quantum chemical calculations.

1. INTRODUCTION Copper is widely used in the production of wire, sheets, pipes, and computers and in the microelectronic industry as well as in the production of a wide range of alloys. In addition, copper is utilized as a construction metal in the cooling systems of nuclear installations, automobile industry, and marine environments. Such extensive use of copper is due to its superior mechanical and electric properties as well as the behavior of its passivation layer. However, copper is very susceptible to corrosion in chloride solutions, especially in marine environments. It is well accepted that the chloride ion has a serious influence on copper corrosion.1,2 Therefore, the corrosion of copper has been widely studied in chloride media and a great number of scientists have investigated the copper dissolution mechanism in chloride solutions.3−7 In recent years, the possibility of copper corrosion inhibition by some organic molecules in aqueous chloride solution has attracted numerous interests because the corrosion inhibition efficiencies could be increased by the appropriate alteration of chemical structures of the organic inhibitors.8−14 It was found that the presence of heteroatoms or heterocycles in the organic molecules could greatly improve the corrosion inhibition efficiency of copper.9−12 It is considered that the presence of the unfilled orbitals in the copper atom yields the coordinated bonds with the heteroatoms. Many efforts were made to utilize hetero-organic molecules as the copper corrosion inhibitors such as azole, amines, and amino acids.15−19 Meanwhile, it is still a great challenge to obtain the highly efficient organic inhibitors to copper in chloride solution through molecular preconstruction. Schweinsberg and co-worker investigated the inhibition efficiencies of alkyl esters of 5-carboxybenzotriazole (CBTAH) with different carbon chains (CBTAH-Me, © 2015 American Chemical Society

CBTAH-Bu, CBTAH-He, CBTAH-Oe) on copper in acidic solution. It was demonstrated that the fatty chain length was significantly positively correlated with the inhibition effect.20 The inhibition efficiencies increased with the increase of the chain length as CBTAH-ME < CBTAH-BU < CBTAH-HE < CBTAH-OE. The highest inhibition efficiency of 98% at the concentration of 1 × 10−4 M of CBTAH-OE was obtained for this family. Similarly, the protective efficiencies of 5-alkylbenzotriazolic derivatives (chain length, n = 1, 6, 8) on copper were determined by Brunoro and his coauthors in acid and neutral rain media.21 The experimental results suggested that 5octyl-1,2,3-benzotriazole could be a promising coating candidate in the bronze conservation field. While unfortunately, the both groups have not determined the inhibition efficiency of CBTAH or BTAH with the longer carbon chains. Jennings and his co-workers reported four sodium S-alky thiosulfates with longer chain length (chain length, n = 8, 10, 12, 14) as the copper inhibitors in HCl solution.22 It was observed that the inhibition efficiencies of these molecules increased with the enhancement in the alkyl chain length in the order as STC14 ≈ STC12 > STC10 ≈ STC8. However, the polar part in inhibitor molecular structure is too small to tightly absorb on the surface of copper, as a consequence, the inhibition efficiencies were not well satisfied. Zhang and his coauthors attempted to improve the inhibition efficiency of undecyl substituted imidazole (UDIM) on copper in chloride media.23 Meanwhile, the inhibition efficiency of UDIM only reached 73% at its optimal concentration, which could be due Received: Revised: Accepted: Published: 12242

August 14, 2015 November 1, 2015 November 18, 2015 November 18, 2015 DOI: 10.1021/acs.iecr.5b02988 Ind. Eng. Chem. Res. 2015, 54, 12242−12253

Article

Industrial & Engineering Chemistry Research

reported. The results presented in this study would benefit the synthesis of new efficient organic corrosion inhibitors for copper in chloride aqueous solution through rational molecular preconstruction.

to the weak adsorption of the polar head on the copper surface as well. Inspired by these efforts of the scientists, it is thought to design the ligands that adsorb strongly with copper in order to achieve the excellent corrosion inhibition of copper with new organic inhibitors. Additionally, the effective organic inhibitors can substitute water molecules from the surface of copper. Hence, the interaction between the anodic and cathodic reaction can retard the oxidation and inhibit the corrosion reactions. As a result, the transportation of water molecules is prevented, and the movement of corrosion active species to the surface of copper is prohibited. In this work, we propose the preconstruction of the polar head and hydrophobic tail type organic inhibitors to copper. Herein, the polar head can attach to the copper surface tightly, and the tail can form a water resistance wall (see Figure 1). Accordingly, the corrosion of copper could be efficiently inhibited by such organic molecules.

2. EXPERIMENTAL SECTION 2.1. Materials and Characterization. The working electrodes were prepared by the pure copper (99.99 wt %). The copper specimens were mechanically cut into 1 cm × 1 cm × 1 cm dimensions, embedded in epoxy resin, and only 1 cm2 was exposed to the air. Prior to all the experiments, the samples were abraded with a series of emory papers (800, 1200, 1500, 2000, and 3000 grade). Then they were ultrasonically cleaned in ethanol and acetone, and finally dried at the room temperature before the inhibition experiments. The new benzotriazole derivatives carrying various fatty chains (n = 1, 3, 4, 6, 7, 9, 10, 12, 16) shown in Scheme 1 were prepared in our laboratory through a multistep routine synthetic route. The preparation and the characterization of the target inhibitor molecules including 1H NMR spectra, FTIR spectra, elemental analysis, and melting point were also presented in this study. 2.2. Determination of Corrosion Inhibition of Copper in 3.5 wt % NaCl Solution. 2.2.1. Electrochemical Measurements. In this study, the standard three-electrode electrochemical cell was used containing the platinum foil as the counter electrode, the saturated calomel electrode (SCE) as the reference electrode, and the copper electrode as the working electrode. The electrochemical determinations in a routine three-electrode cell system were processed by PARSTAT 2273 Potentiostat/Galvanostat. All the potentials were measured versus the saturated calomel electrode (SCE) with a Luggin capillary was used as the reference electrode. The detection was carried out in the air saturated solution. The polarization curves were obtained from −250 to +250 mV (versus open circuit potential (OCP)) with 0.5 mV·s−1 scan rate, and the data were collected and analyzed. The electrochemical impedance spectroscopy (EIS) measurements were performed at the OCP. The ac frequency range was extended from 100 kHz to 10 mHz with a 10 mV peak-to-peak sine wave, and the impedance data were analyzed and fitted. 2.2.2. Weight Loss Measurement. The copper specimens used for the weight loss experiments were rectangular in shape with the dimensions of 2 cm × 2 cm × 1 cm. After the weighing, the treated specimens were suspended in 250 mL of 3.5 wt % NaCl solution with and without different concentrations of inhibitors for 15 days. The weight loss experiments were performed five times, and the mean weight loss was calculated. 2.2.3. Scanning Electron Microscope. The surface morphology of the copper sample after immersion in 3.5 wt % NaCl solution containing various organic inhibitors respectively was performed on a KYKY2800B scanning electron microscope. The accelerating voltage was 5 kV. 2.3. Molecular Modeling. The molecular modeling was performed by means of Gaussian 09 program package. The geometry optimization of all the organic inhibitors for the ground electronic state was performed at DFT level using B3LYP method both with 6-311++G (d,p). The quantum chemical parameters association with corrosion inhibition were calculated including the energy gap (ΔE = ELUMO − EHOMO), the ionization (I), the electron affinity (A), the dipole moment

Figure 1. Scheme of the “blocking water layer.”

Thus, a range of benzotriazole derivatives were synthesized in this study. The molecular structures are composed by the polar heterocycle (trinitrogen ring) part as the “adsorption head”, and the apolar hydrophobic fatty carbon chain part as the “blocking water tail” (see Scheme 1 in the Experimental Scheme 1. Chemical Structures of the Molecules Studied in This Work

Section). It is well accepted that the excess long fatty carbon chain could automatically curl itself,24 which could result in negative effects on not only the adsorption but also the water resistance. Therefore, the length of carbon chain attached to the molecular backbone could lead to remarkable effect on the corrosion inhibition efficiency of copper. In this work, the corrosion inhibition effect of these new molecules to copper in chloride aqueous solution was completely studied by using the polarization curve, the electrochemical impendence spectroscopy (EIS), the weight loss method and the scanning electron microscopy (SEM). To the best of our knowledge, no investigation on the 2-(2′phenyl)-2H-benzotriazole derivatives as the efficient corrosion inhibitors for copper in 3.5 wt % NaCl solution has been 12243

DOI: 10.1021/acs.iecr.5b02988 Ind. Eng. Chem. Res. 2015, 54, 12242−12253

Article


densities significantly decrease in the present of different concentrations of C5, while the curve shapes are quite similar. This suggests that the electrochemical mechanism in the anodic and cathodic regions is not varied by the addition of the organic inhibitor molecules. It is considered that the anodic dissolution of copper is shown in the following eqs 1−3. Figure 2 shows that the anodic branch of Cu in NaCl solution shows three distinct regions. First, the current density increases from the lower anodic potentials to a peak value (ipeak) because of the oxidation of Cu0 to Cu+.

(μ), the electronegativity (η), the global hardness (δ), and the fraction of electrons transferred (ΔN). The molecular mechanics simulation was carried out with Discover module in Materials Studio software. The interaction between the inhibitors and copper surface was assumed in a simulation box (3.067 nm × 3.067 nm × 1.627 nm) with periodic boundary condition. The copper layer with 0.181 nm thickness was cleaved along the (1 0 0) plane. All the spatial positions of copper atoms (11 layers containing 1331 Cu atoms) were fixed. The thermal vibrations of these metal atoms were not considered in the computation. The single inhibitor molecule was simulated to be in a box which contains 1500 H2O molecules, and it was adsorbed on copper surface. The system was optimized by Smart Minimizer method based on COMPASS force-field. 2.4. Preparation of the Target Organic Inhibitors. The synthesis of the target molecules is shown in Scheme 1. The azotizing was finished by the dropwise of sodium nitrite aqueous solution into the o-nitroaniline solution. And the diazonium salt was obtained by dropping the above azo solution into the phenol solution. The intermediate 2-(2Hbenzotriazol-2-yl)-phenol was obtained through the reduction of the diazonium using zinc powder. The target inhibitors were prepared through the alkylation of 2-(2H-benzotriazol-2-yl)phenol by corresponding alkyl iodide or alkyl bromide.25

Cu → Cu+ + e−

(1)

Second, the insoluble film CuCl is immediately yielded in the presence of Cl−. The current density decreases from the ipeak to a minimum value (imin). Cu+ + Cl− → CuCl

(2)

At the end, the unstable CuCl is further attacked by Cl−. As a consequence, the soluble complex CuCl2− is rapidly formed. And the current density increases suddenly from imin to the higher anodic potentials. CuCl + Cl− → CuCl −2

(3)

It is further considered that the cathodic corrosion reaction in NaCl solution is the reduction of the oxygen:

3. RESULTS AND DISCUSSION 3.1. Electrochemical Polarization. The polarization curves of copper in 3.5 wt % NaCl solution with and without different concentrations of the inhibitors C1−C9 were measured. The representative polarization curves of the systems with C5 are shown in Figure 2. It is found that the current

O2 + 4e− + 2H 2O → 4OH−

(4)

As shown in Figure 2, both the cathodic and anodic current densities decrease with the addition of C5 comparing with the blank NaCl solution, and it implies that C5 can effectively suppress the anodic and cathodic reaction processes simultaneously. As the suppression on the cathodic domain is more pronounced, suggesting that the influence of C5 on the cathodic reaction is greater than that on the anodic reaction. This phenomenon could be attributed to the modification of the anodic dissolution process because the inhibitor molecules absorb on the active sites, which gives rise to the decrease of the corrosion sites of chloride ions.26 Table 1 shows the electrochemical parameters obtained from the Tafel plots of the copper electrode in 3.5 wt % NaCl solution with and without different concentrations of the inhibitor C5. The values of the corrosion potential (Ecorr), cathodic and anodic Tafel slope (βc, βa), and the corrosion current density (jcorr) are calculated from Tafel extrapolation method. The inhibition efficiency (IEj%) can be calculated by the following equation:

Figure 2. Polarization curves for copper in 3.5 wt % NaCl solution with and without different concentrations of C5 at 298 K.

IEj% =

0 jcorr − jcorr 0 jcorr

× 100 (5)

Table 1. Polarization Parameters for the Copper in 3.5 wt % NaCl Solution without and with Different Concentrations of C5 at 298 K inhibitors blank C5

C (M, mol·L−1) × 105

Ecorr (V·SCE−1)

jcorr (μA·cm−2)

βc (mV·dec−1)

βa (mV·dec−1)

IEj (%)

2 6 10 15 20

−0.192 −0.203 −0.217 −0.221 −0.232 −0.229

5.233 1.875 1.530 0.773 0.098 0.424

−80 −78 −69 −64 −58 −62

232 252 192 201 129 170

 64.17 70.75 85.23 98.12 91.90

12244


Article


Figure 3. Nyquist (a), Bode (b), and phase angle (c) plots for copper in 3.5 wt % NaCl solution without and with different concentrations of C5 at 298 K.

wherein j0corr and jcorr are the corrosion current densities of copper electrode in 3.5 wt % NaCl solutions with the presence or absence of the inhibitors, respectively. It is thought that an organic inhibitor can be regarded as either anodic-type or cathodic-type if the change in Ecorr value is above 85 mV (SEC).27,28 In comparison with the bare copper, Ecorr values in the presence of the inhibitor C5 slightly move to the negative direction, and the displacements are less than 85 mV (SEC). It is suggested that the target inhibitor C5 plays the mixed-type inhibitor roles. Table 1 shows that with the increase of the concentration of C5 from 0.02 to 0.15 mM in NaCl solution, icorr value reduces from 1.875 to 0.098 μA·cm−2, and IEj value increases from 59.63% to 98.12%. This indicates that the film formed on the copper surface becomes denser with the increase of the concentration of C5. Therefore, the copper could be effectively protected by C5 in chloride aqueous solution. On the other hand, as the concentration of C5 exceeds 0.15 mM, IEj value decreases (91.90% at 0.20 mM). This could be caused by the steric effect that the adsorbed molecules rearrange on the copper substrate as soon as the adsorption of the inhibitor molecules reaches a certain value.29 As a result, the corrosive chloride ions easily attack the copper through the interspaces. The variations of βc and βa with the increase of the concentration of the target C5 demonstrate that both the anodic and cathodic reactions are suppressed by the organic inhibitor film.

In the case of all the inhibitors with the concentration of 0.15 mM, the highest inhibition efficiency for the each inhibitor is obtained. The polarization curves at the optimal concentration the corresponding electrochemical parameters are shown in Figure S1 and Table S1 respectively (see the Supporting Information). The results show that the corrosion current density increases with the increase of the carbon chain length as the carbon number is less than 7 (such as to C1−C3, 2.112, 1.501, 0.727 μA·cm−2). The greatest inhibition efficiencies of C1, C2, C3, C4, and C5 are 59.63%, 71.32%, 86.11%, 94.39% and 98.12%, respectively. On the other hand, the highest inhibition efficiencies decrease with the further enhancement of the carbon chain length. The inhibition efficiencies of C6, C7, C8, and C9 are 91.18%, 87.86%, 85.85%, and 82.75%, respectively. It is worthy pointing out that C5 exhibits the greatest inhibition efficiencies among these new inhibitors at various concentrations. This means that 7-carbon atoms fatty chain in the inhibitor is the most favorable for the corrosion inhibition effect of copper in NaCl solution. The influence of the chain length on the inhibition efficiency is further analyzed in the following sections. 3.2. Electrochemical Impedance Spectroscopy (EIS). EIS measurements were carried out to investigate the corrosion inhibition effect of C1−C9 as well as the kinetics of the corrosion reaction process. The representative spectra of Nyqusit, Bode, and phase angle of copper electrodes without and with various concentrations of C5 at the open circuit 12245


Article


The corresponding impendence parameters for R(Q(R(Q(RW)))) are given in Table 2. Herein, Rs represents the resistance of the solution between the working and the reference electrodes. Rct is the charge transfer resistance corresponding to the corrosion reaction at the copper−solution interface. Rf is the film resistance from inhibitors and the inevitable oxide species. W is the Warburg impendence induced by the diffusion of corrosive reactants or corrosion produce species. The constant phase elements CPEf and CPEdl are used to replace the film capacitance and the double layer capacitance, respectively. The impedance of CPE is defined by the following equation:

potential immersed in 3.5 wt % NaCl solution for 40 min respectively are shown in Figure 3a−c. All the impendence plots show the typical semicircles in the high frequency areas following by the straight line at the low frequency area. The high frequency semicircle is attributed to the time constant of the charge transfer and the double-layer capacitance.30 The low frequency line is attributed to Warburg impendence, which is yielded by the diffusion of the dissolved oxygen to the copper surface or the diffusion of chloride−copper complexes from the copper electrode to the bulk solution.31 The presence of W in bare copper system indicates that the diffusion is limited. In other words, there is a passive film coated on the copper surface as well. In NaCl solution, the other corrosion products could be formed except CuCl. The oxidation of Cu0 by the dissolved oxygen occurs on the interface and Cu2O is generally produced. And then Cu2O is directly oxidized to CuO, which usually covers on the copper surface. In our system, the bare copper shows W character and the corrosion rate of copper could be decrease to some extent by the presence of copper oxide. For the copper electrodes covered with these organic inhibitors, large semicircles are shown at the high frequency area in Nyquist plots and the diameters of the semicircle gradually increase with the increase of the concentrations of C5, suggesting the formation of the inhibitor molecular protective film. Figure 3a suggests that the diameter of the capacitive loop reaches the maximum at 0.15 mM of C5. On the other hand, the shapes of the Nyquist plots for the inhibited copper electrodes are not substantially different from those of the uninhibited copper electrode. This suggests that C5 does not alter the corrosion mechanism of copper in 3.5 wt % NaCl solution.32 Bode plots (Figure 3b) show that the impendence values over the whole frequency range greatly increase with the increase of the concentrations of C5, and the values of the impendence reaches the peak as its concentration is 0.15 mM, meaning that the best inhibition corrosion protection is obtained.33 Furthermore, Figure 3b shows that the phase angle displays an enhancement with the increase of the concentrations of C5, which indicates the increase of the inhibitor molecules adsorption on the electrode surface.34 It is obtained from Bode phase plots that the corrosion process of C5 possesses two relaxation time constants. One is dependent on the relaxation of the electrical double layer capacitor, and the other is involved with the relaxation process of the adsorbed organic inhibitors. Figure 4 shows the equivalent circuit model for the analysis of the impendence characteristics. This model was reported to study for the copper−chloride solution interface,35 and it produces the less error and the chi-square value (χ2) is lower than 1 × 10−3.

ZCPE =

1 Y (iω)n

(6)

wherein Y is the proportional factor, ω is the angular frequency, n is the deviation parameter, and i is the imaginary unit. The capacitance values of CPEdl can be calculated from CPE parameter values Y and n using eq 7. Cdl =

Yωn − 1 sin(nπ /2)

(7)

The addition of the inhibitor provides the lower Y values, which is the consequence of the replacement of water molecules by the organic inhibitor molecules at the electrode surface. In addition, n value has a tendency to decrease with increase of the concentration of the organic inhibitors, which is the indication of the adsorption of organic molecules on copper surface.36 The thickness of the protective layer (d) is related to CPEdl according to the expression of the layer capacitance presented in Helmholtz model: Cdl =

ε 0ε A d

(8)

wherein d is the thickness of the film, A is the surface area of the electrode, ε0 is the permittivity of the air, and ε is the local dielectric constant. Equation 8 means that Cdl in the inhibitor systems could be lowered by the increase of the adsorption film area (meaning that electrode surface area is lowered), the decrease in the local dielectric constant, and/or the increase in the thickness of the protective layer.37 The polarization resistance Rp is expressed by eq 9:

R p = R ct + R f

(9)

then, the inhibition efficiency (IEp%) can be calculated by the following equation: IEp% =

R p0 − R p R p0

× 100 (10)

R0p

wherein Rp and are polarization resistance in the presence and absence of the inhibitors, respectively. Table 2 shows that Rf values of C5 increase, while its Cf values decrease until the optimal concentration appears (Rf: 109.4, 162.0, 294.0 Ω·cm2. Cf: 39.75, 30.93, 24.05 μF·cm−2 for 0.06, 0.10, 0.15 mM). This is due to the ionic conductivity of the surface film which decreases with the increase of the concentration of the inhibitors. If it is considered that the ionic conduction through the film is ensured by the pores crossing the film and the increase of the film thickness, the total surface of the pores could then be dramatically reduced with the addition of the inhibitor molecules. It is worthy to notice that in

Figure 4. Equivalent circuit model used to fit the EIS experiment data. 12246


Article


Table 2. Electrochemical Parameters Calculated from EIS Measurements for Copper in 3.5 wt % NaCl Solution with Different Concentrations of C5 at 298 K CPEf inhibitors blank C5

CPEdl

c/mM

Rsa

Rf a

Rcta

Cfb

n1

Cdlb

n2

Wc

IEp(%)

0.02 0.06 0.10 0.15 0.20

1.70 3.22 4.91 5.14 6.63 4.69

23.2 58.5 109.4 162.0 294.0 130.1

0.25 0.72 0.77 2.07 13.14 2.59

163.82 60.53 39.75 30.93 24.05 42.80

0.90 0.88 0.90 0.88 0.87 0.91

170.35 155.32 103.91 69.90 29.98 40.72

0.97 0.70 0.65 0.66 0.69 0.70

4777 2569 2018 1611 782 1517

65.31 71.25 87.89 97.99 90.07

a

Rct are expressed in kilo-ohm squared centimeters, while Rs and Rf are expressed in ohm squared centimeters. bCdl and Cf are given in microfarad per squared centimeter. cW is given in micro-ohm per squared centimeter.

Figure 5. Variations of the weight loss (a) and pH value (b) with time for copper in 3.5 wt % NaCl solution with different concentrations of C5 at 298 K.

the greater Rp of 13.14 kΩ·cm2 than the other inhibitors. As a consequence, C5 exhibits the larger inhibition efficiency 97.99% than the other inhibitors at the concentration of 0.15 mM. It is suggested that the inhibitor C5 carrying a 7-carbon chain length shows the most excellent inhibition corrosion efficiency among these inhibitors, which agrees well with the result of the polarization curves. When the carbon chain length is less than 7 carbon atoms, the inhibition corrosion efficiency increases with the increase of carbon chain length (C1 56.72%, C2 73.79%, C3 88.11%, C4 93.98%, C5 97.99%). When the carbon chain length is larger than 7 carbon atoms, the inhibition corrosion efficiency decreases with the increase of carbon chain length (C6 93.79%, C7 90.35%, C8 87.20%, C9 85.39%). The further analysis of the interrelationship between the carbon chain length and the inhibition corrosion efficiency of the inhibitors is presented in the following sections. 3.3. Weight Loss Experimental Results. The variations of the weight loss versus the immersion time for the copper specimen in 3.5 wt % NaCl solution containing different concentrations of C5 are shown in Figure 5a. And the corresponding changes in pH values of the above solution are presented in Figure 5b. The results show that the weight loss of copper in chloride solution without the inhibitors reaches 47.1 mg·m−2 in 3 days and 254.4 mg·m−2 in 15 days (Figure 5a). Meanwhile, the corresponding change in pH values of the solution increases from 6.4 to 8.6 (Figure 5b). The results suggest that a significant amount of copper in the form of CuCl2− is dissolved into the solution.40 Because the cathodic couple of the corrosion reaction of copper is the reduction of

most cases, the values of Rct are approximate 2 orders of magnitude higher than those of Rf, which indicates that the inner barrier layer plays the most important role in the corrosion process of copper protection in the studied system.38 Table 2 also reveals that Rct increases with the enhancement of the concentration of C5 (0.77, 2.07, 13.14 kΩ·cm2 for 0.06, 0.10, 0.15 mM). This suggests that the protecting film on the electrode surface is formed. This phenomenon also indicates that the charge transfer process is impeded as the uncovered area for this process is diminished due to the adsorption of more inhibitor molecules at the copper/electrolyte interface. Cdl decreases in the presence of C5 comparing with the blank solution (170.35 μF·cm−2 for blank, 155.32 μF·cm−2 for 0.02 mM, 29.98 μF·cm−2 for 0.20 mM), which is due to the gradual replacement of water molecules by the adsorption of organic molecules at the electrode surface, leading to the production of a protective film on the copper surface which prevents the mass and charge transfers.39 Accordingly, the extent of the dissolution reaction of cooper is inhibited in NaCl solution. It is noticed that the other target inhibitors also show similar electrochemical properties as C5. Nyqusit plots of all the organic inhibitors and the corresponding electrochemical parameters at the optimal concentration are presented in Figure S2 and Table S2 respectively (in the Supporting Information). As compared with the bare copper electrode, Cf, Cdl, and W of these inhibitors tend to decrease and the Rp greatly increases. The minimal values of Cf, Cdl, and W and the maximum of Rp are obtained at the optimal concentration of 0.15 mM for all the inhibitors. And it is observed that C5 has 12247


Article

Industrial & Engineering Chemistry Research Table 3. Thermodynamic Parameters for the Adsorption of C1−C9 in 3.5 wt % NaCl Solution at 298 K inhibitor

C1

C2

C3

C4

C5

C6

C7

C8

C9

slope ΔG0ads (kJ·mol−1)

0.830 −32.34

0.850 −33.98

0.900 −35.07

0.950 −38.01

0.995 −38.15

0.920 −37.05

0.880 −35.98

0.860 −35.47

0.800 −34.91

oxygen, the rate of generation of OH− ions is the same as that of CuCl2− ions (eq 4). Thus, the corrosion process is coupled with a surface alkalinization. This indicates the increase of copper dissolution with the increase of both the immersion time and pH values.41 As seen from Figure 5a and b, the increasing rate of both the weight loss and the corresponding pH values significantly decreases in the presence of C5 at quite low concentration (the corrosion rate without and with 0.02 mM of C5: 0.706 and 0.273 mg·m−2·h−1). This effect gradually increases with the increase of the concentrations of C5 (the corrosion rate with 0.06, 0.10, and 0.15 mM of C5: 0.127, 0.086, and 0.013 mg· m−2·h−1). Thus, the inhibitor C5 exhibits the neat protection ability to copper by the observation of the slight loss of the weight and small changes of pH values. This is due to the adsorption of organic molecules on copper surface, which could keep the copper surface from the corrosion caused by chloride ion and prevent the formation of cuprous chloride and oxychloride complexes. As the concentration of C5 is above 0.15 mM, the loss of copper weight and pH value of the solution tend to increase, which further demonstrates that there is the presence of an optimal concentration of C5 for its inhibition corrosion effect of copper. Our further survey shows that the other inhibitors also display similar phenomena to C5. Both the weight loss of copper and corresponding pH value of the solution decrease in the presence of these inhibitors (the corrosion rate without and with 0.15 mM of C1, C3, C7 and C9: 0.706, 0.317, 0.083, 0.068, and 0.103 mg·m−2·h−1). Additionally, the weight loss and pH value become the minima at 0.15 mM of all the inhibitors respectively, meaning the greatest inhibition efficiencies are obtained at this concentration of these inhibitors. The variations of weight loss and pH value with the immersion time at the optimal concentration of all the target inhibitors are given in Figure S3a and b, respectively (in the Supporting Information). It is observed that C5 possesses the highest inhibition effect among these inhibitors, which is consistent with the above electron chemical determination. The inhibition efficiency of inhibitor, IEw%, for the corrosion of copper is obtained by using the following equations:

v=

W St

3.4. Adsorption Isotherm. It is known that the basic information on the interaction between the organic inhibitor and the copper surface could be provided by the adsorption isotherm.42 The degrees of surface coverage (θ) for different concentrations of the inhibitors in 3.5 wt % NaCl solution can be calculated by the weight loss measurement by using the following equation: θ=

v0 − v v0

(13)

wherein v0 and v are the corrosion rates of the copper sample without and with inhibitor, respectively. And, the surface coverage data are useful in the survey of the inhibitor adsorption characteristics. The surface data is used to fit to a series of adsorption isotherms containing those of Flory− Huggins, Dhar−Flory−Huggins, Bockris−Swinkels, Freundlich, and Langmiur.43 This demonstrated that the adsorption of the inhibitors obeys the Langmiur isotherm (eq 14) because the linear regression coefficients (R2) are almost close to 1.0 in all the cases. c 1 = +c θ kads

(14)

wherein kads is the equilibrium constant of the inhibitor adsorption process, c is the inhibitor concentration, and θ is the degree of surface coverage. The nature of corrosion inhibition could be deduced in terms of the adsorption characteristics of the inhibitor.44 In aqueous solution, the metal surface is always covered with the adsorbed water molecules. The adsorption of these inhibitors on copper surface is regarded as the substitution adsorption process occurring between the inhibitor molecules in aqueous phase and the water molecules adsorbed on copper surface. According to Langmuir isotherm theory, an inhibitor molecule substitutes a water molecule on the metal surface during the adsorption process, then the equilibrium constant kads can be calculated by the following equation:45 0 kads =

⎛ ΔG 0 ⎞ 1 ads ⎟ exp⎜ − 55.5 ⎝ RT ⎠

(15)

thus 0 0 ΔGads = −RT ln(55.5kads )

(11)

(16) −1

v0 − v IE w % = × 100 v0

−1

wherein R is the molar gas constant (8.314 J·mol ·K ), T is the absolute temperature, and the value 55.5 is the molar concentration of water in solution with units of kilojoules per mole. It is widely accepted that the standard free energy of adsorption values of −20 kJ·mol−1 is associated with an electrostatic interaction between the charged molecules and the charged metal surface (physical adsorption). While those of −40 kJ·mol−1 or more negative values mean the charge sharing or transfer from the organic inhibitor molecules to the metal surface to form the covalent bond (chemical adsorption).46 Table 3 shows the that the values of ΔG0ads range from −32 to −39 kJ·mol−1, indicating that the adsorption of these inhibitors involves mixed-type interactions: chemical and physical adsorption. In addition, Figure S4 (in the Supporting

(12)

wherein W is the weight loss of the copper specie, S is the total surface area of the sample, t is the immersion time, v0 and v are the corrosion rates of the copper sample without and with inhibitor, respectively. This agrees with the above electrochemical determination that C5 shows the best inhibition efficiency of 98.45%. Similarly, the inhibition efficiencies increase as the carbon chain length is shorter than 7 (C1 58.12%, C2 72.84%, C3 89.98%, C4 93.00%, C5 98.45%), and they decrease as the carbon chain length is longer than 7 (C6 92.93%, C7 88.18%, C8 87.37%, C9 84.98%). 12248


Article


Figure 6. SEM micrographs of the surface of Cu, (a) before and after being immersed for 15 days in 3.5 wt % NaCl solutions: (b) without inhibitor, (c) with 0.15 mM of C5, (d) after the removal of the inhibiting film.

Figure 7. EDS analysis of copper surface of presented in (a) Figure 6a and (b) Figure 6c.

Information) shows that C5 yields the best fit to the Langmiur isotherm with the slope nearly approaching 1.0, and C5 possesses the maximal value of adsorption free energy (the slopes for C1, C3, C5, C7: 0.830, 0.900, 0.995, 0.880). Furthermore, the adsorption free energies of the inhibitors follow the same order as the inhibition efficiencies obtained by the weight loss method (the adsorption free energies for C1− C9: −32.34, −33.98, −35.05, −38.01, −38.15, −37.05, −35.98, −35.47, −34.91 kJ·mol−1). These indicate that C5 could show the tightest adsorption on copper surface among these inhibitors. The results suggest that the length of carbon chain attaching to the molecular backbone does affect the adsorption of the inhibitor on copper so thus the corrosion inhibition effect is affected accordingly. 3.5. SEM and Energy Dispersive Spectrometer (EDS) Analysis. The surface morphology of copper sample immersed in 3.5 wt % NaCl solution for 15 days in the absence and in the presence of 0.15 mM of C5 was studied by scanning electron microscopy (SEM). Figure 6 shows the surface morphology of

copper specimens (a) before, (b) after being immersed in 3.5 wt % solution, (c) after being immersed in the corrosive solution of C5, and (d) after the removal (by ethanol) of the inhibiting film. It is evidently found that the naked copper is covered with nicks and lines (Figure 6a), because the copper surface is abraded with SiC abrasive papers and retains a polished surface. In contrast to the specimen before the immersion (Figure 6a), the specimen in the absence of the inhibitors (Figure 6b) is strongly corroded by the chloride medium, resulting in the formation of the rough surface. However, in the presence of C5, negligible corrosion is observed in Figure 6d. The nicks caused by the initial surface abrasion remain clearly visible after 15 days immersion as shown in Figure 6d. Figure 6c shows the specimen covered with the inhibiting layer which was immersed in the solution containing 0.15 mM of C5 and then it was washed briefly with water, thoroughly dried, and mounted into the spectrometer without any further treatment. It is observed that the copper surface is covered with a scaly and dense 12249


Article


Table 4. Contents of the Elements on the Copper Surface Obtained from EDS after Immersion in 3.5 wt % NaCl Solutions without and with Different Concentrations of C5 at 298 K concentration

C (wt %)

blank C5 0.02 0.06 0.10 0.15 0.20

N (wt %)

O (wt %)

Cl (wt %)

0

0

0

0

2.21 2.55 3.01 4.35 4.01

1.65 1.89 2.67 3.00 2.12

1.21 2.34 4.21 7.44 5.33

0.35 0.65 1.11 1.22 1.51

organic film which successfully prevents the copper surface corrosion, and the nicks are also clearly visible. Figure 7 presents the results of EDS analysis. The copper, carbon, nitrogen, chloride, and oxygen are determined after the immersion in the solution during 15 days. The content of each element on copper surface obtained from EDS after the immersion in 3.5 wt % NaCl solutions without and with inhibitors for different days at 298 K is shown in Table 4. The results show that the composition of the detected elements on the copper surface which was immersed in 3.5 wt % NaCl solution containing 0.15 mM C5 for 15 days included 4.35% C, 3.00% N, 7.44% O, 1.22% Cl, and 83.99% Cu, respectively. This indicates that the organic inhibitor molecules are strongly adsorbed on the copper forming the Cu−C5 bond, preventing corrosion. This also explains the large decrease of the currents as the concentration of C5 increases and the significant increase in Rct values (see Table 2). The previous studies demonstrated that nitrogen heterocycle molecules could self-assemble on the surface of coinage metals such as copper, silver, and gold by yielding strong covalent bonds between the nitrogen atoms and the metal surface.47 In the present system, C5 could form selfassembled layers on copper surfaces. 3.6. Quantum Chemical Calculations and Molecular Dynamics Simulations. The frontier molecular orbital density distributions of C5 are presented in Figure 8. It is

Cu (wt %) 100 94.58 92.57 89.00 83.99 87.03

charge center which could offer electrons to the copper atoms on the metal surface to form a coordinate bond. Therefore, these inhibitors are likely adsorbed onto the copper surface with the hetero ring. It is noticed that the other inhibitors show the similar frontier orbital nature as C5. According to Koopman’s theorem,48 the values of EHOMO and ELUMO of the inhibitor molecule are association with the ionization potential (I) and the electron affinity (A), respectively. The ionization potential and the electron affinity are defined as −EHOMO and −ELUMO, respectively. The obtained values of the ionization potential (I) and the electron affinity (A) are used to calculate the electronegativity (δ) and the global hardness (η). The fraction of electrons transferred from the inhibitor molecules to the metallic atom (ΔN) is calculated according to Pearson’s theory, as shown in eq 17. ΔN =

δCu − δinh 2(ηCu + ηinh)

(17)

wherein the theoretical value for the electronegativity of bulk copper, δCu = 4.48 eV, is used,49 and a global hardness of ηCu = 0 was used. And the electronegativity (δinh) and the global hardness (ηinh) of the inhibitor molecule are approximated as the following equations. δ=

I+A 2

(18)

η=

I−A 2

(19)

Table 5 suggests that C5 has the lowest values of the energy gap and the global hardness among these inhibitors, which indicates that C5 could offer the electrons to an acceptor more easily than others. The fraction of the transferred electrons increases with the extension of carbon chain length from 1−7 (C1 0.1183, C2 0.1186, C3 0.1197, C4 0.1200, C5 0.1207), and it tends to be stable for chain lengths longer than 7. Then, C5 has the best inhibition efficiency in theory.

Figure 8. Frontier molecular orbital density distributions of C5.

shown that the HOMO is mainly focused on the trinitrogen hetero and aromatic ring, indicating that the ring is a negative

Table 5. Quantum Chemical Parameters Calculated by Gaussian 09 with the B3LYP Method at the 6-31++ G (d,p) Level for Benzotraizole Derivatives inhibitor

C1

C2

C3

C4

C5

C6

C7

C8

C9

ΔE (eV) I = −EHOMO (eV) A = −ELUMO(eV) δ η ΔN

−4.6313 6.2479 1.6166 3.9323 2.3157 0.1183

−4.6327 6.2468 1.6142 3.9305 2.3163 0.1186

−4.6346 6.2427 1.6082 3.9255 2.3173 0.1197

−4.6305 6.2395 1.6090 3.9242 2.3152 0.1200

−4.6280 6.2354 1.6074 3.9214 2.3140 0.1207

−4.6286 6.2365 1.6079 3.9222 2.3143 0.1205

−4.6289 6.2365 1.6076 3.9221 2.3144 0.1205

−4.6294 6.2365 1.6071 3.9218 2.3147 0.1206

−4.6294 6.2362 1.6068 3.9215 2.3147 0.1206

12250


Article


molecules (6.39 kcal·mol−1). This suggests the possibility of gradual substitution of water molecules from the surface of copper surface resulting in the formation of the stable organic layer which can efficiently protect the copper from the corrosion. 3.7. Influence of Carbon Chain Length on Corrosion Inhibition. Figure 10 shows the variations of the inhibition

The above results reveal that the carbon chain length attaching to the inhibitor molecule has great influence on the quantum chemical parameters. This theoretically demonstrates that the carbon chain length could cause the effects on the adsorption of the inhibitor molecules on the metal. In the following, we perform further molecular dynamics calculation on the adsorption of the inhibitors on the copper surface. The most stable low energy adsorption configurations of the inhibitors on the Cu(1 0 0)/H2O system using Discover simulations are depicted in Figure 9. For all the cases, the polar

Figure 9. Most stable low energy configuration for the adsorption of C5 and C9 on the Cu(1 0 0) surface, representations obtained using Discover simulations.

trinitrogen and aromatic rings attached to the metal surface horizontally are aligned to the surface, and the apolar tail is orthogonally arrayed. The strong bonding of the heteroatoms (N) of the inhibitors with the Cu atom ensures the transfer of electron density from the active sites of the inhibitors to the dorbital of the copper surface. When the length of the carbon chain increases over 7, as with carbon atoms such as C9 (Figure 9b), the carbon chain tends to bend itself to a certain extent. The adsorption energy can be calculated as follows: Eads = Etotal − (Einhibitor + Eslab + E water)

Figure 10. Variations of inhibition efficiency with chain length.

efficiency obtained by the polarization curves, the electrochemical impedance spectroscopy, and the weight loss method versus the carbon chain length. All trends of those lines are identical. It is shown that the inhibition efficiency of these inhibitors is more related to the length of carbon chain covalently attaching to the inhibitor molecules. The inhibition efficiency increases sharply with extension of the fatty chain length from 1 to 6 and reaches the maximum as the carbon chain length is 7. It is considered that the inhibitors possess the same heteroring adsorbing at the copper surface. The carbon chain of an inhibitor molecule points to the chloride solution and evenly arranged. As a consequence, the hydrophobic blocking wall is formed by many carbon chains, preventing the chloride ion interaction with copper. Then, the longer the chain, the thicker the film and the higher inhibition efficiency. Combining with the above theoretical quantum chemical calculation, it is shown that the carbon chain attaching to the molecular backbone of these inhibitors affects not only the adsorption of the molecules on the metal but water resistance by the formation of blocking wall. On the other hand, a carbon chain that is too long tends to curl itself up and can not extend to its full length. It is well-known that the fatty chain could possess the ability to curl itself when the carbon number is over 7. Consequently, the inhibition layer formed by the too long carbon chain becomes loose and porous, and it could not efficiently keep the chloride ions away from the interface. Therefore, the inhibition efficiency decreases when further increasing the length of the carbon chain. While the inhibition efficiency decreases as the length of the carbon chain is over 7

(20)

wherein Eads denotes as the interaction energy of Cu surface with the inhibitors, Etotal represents the total energy of Cu crystal together with the adsorbed inhibitor molecules and water molecules, Einhibitor and Eslab show the total energy of isolated inhibitor-molecule and clean Cu-slab, respectively, and Ewater is the energy of water molecules. The adsorption energies calculated from the Discover simulations are listed in Table 6. It is seen from Table 6 that the adsorption energies of the inhibitors on copper surface in the presence of water decrease in the following order C5 > C4 > C6 > C7 > C3 > C8 > C9 > C2 > C1. This result agrees with the experimental determined inhibition efficiencies by the electrochemical methods and the weight loss experiments. C5 yields the greatest corrosion inhibition effect, while C1 ranks the least corrosion inhibition efficiency among these inhibitors. It is also consistent with the quantum chemical computations. It is well-known that the primary mechanism of corrosion inhibitor interaction with copper lies in the adsorption. Then the adsorption energy of the inhibitor molecules can provide us a direct indication to rank the inhibition efficiencies. The higher negative adsorption energy indicates a system with more stable and strong adsorption. In all the cases, the adsorption energies of the inhibitors C1−C9 are much higher than that of water

Table 6. Adsorption Energies Calculated by Dynamic Simulations for C1−C9 inhibitor

C1

C2

C3

C4

C5

C6

C7

C8

C9

Eads(kcal·mol−1)

−47.12

−49.56

−51.54

−52.01

−52.91

−52.25

−51.84

−49.11

−49.08

12251


Industrial & Engineering Chemistry Research carbon atoms, it tends to become constant (∼85%) when the chain length is increased further, as shown in Figure 10.

ACKNOWLEDGMENTS

■

REFERENCES

(1) El-Sherif, R. M.; Ismail, K. M.; Badawy, W. A. Effect of Zn and Pb as alloying elements on the electrochemical behavior of brass in NaCl solutions. Electrochim. Acta 2004, 49, 5139−5150. (2) Kabasakaloglu, M.; Kryak, T.; Sendil, O.; Asan, A. Electrochemical behavior of brass in 0.1 M NaCl. Appl. Surf. Sci. 2002, 193, 167−174. (3) Braun, M.; Nobe, K. Electrodissolution kinetics of copper in acidic chloride solutions. J. Electrochem. Soc. 1979, 126, 1666−1671. (4) Moreau, A. Etude du mecanisme d’oxydo-reduction du cuivre dans les solutions chlorurees acides II. Systemes Cu CuCl CuCl2− et Cu Cu2(OH)3Cl CuCl+ Cu2+. Electrochim. Acta 1981, 26, 1609−1616. (5) Crundwell, F. K. The anodic dissolution of copper in hydrochloric acid solutions. Electrochim. Acta 1992, 37, 2707−2714. (6) Deslouis, C.; Mattos, O. R.; Musiani, M. M.; Tribollet, B. Comments on mechanisms of copper electrodissolution in chloride media. Electrochim. Acta 1993, 38, 2781−2783. (7) da Costa, S. L.; Agostinho, S. M.; Nobe, K. Rotating Ring-Disk Electrode Studies of Cu-Zn Alloy Electrodissolution in 1M HCl Effect of Benzotriazole. J. Electrochem. Soc. 1993, 140, 3483−3488. (8) Zhou, G. D.; Shao, H.; Loo, B. H. A study of the copper electrode behavior in borax buffer solutions containing chloride ions and benzotriazole-type inhibitors by voltammetry and the photocurrent response method. J. Electroanal. Chem. 1997, 421, 129−135. (9) Villamil, R. F. V.; Corio, P.; Rubim, J. C.; Agostinho, S. M. L. Sodium dodecylsulfate-benzotriazole synergistic effect as an inhibitor of processes on copper|chloridric acid interfaces. J. Electroanal. Chem. 2002, 535, 75−83. (10) Sherif, El M.; Erasmus, R. M.; Comins, J. D. Effects of 3-amino1,2,4-triazole on the inhibition of copper corrosion in acidic chloride solutions. J. Colloid Interface Sci. 2007, 311, 144−151. (11) Cai, L.; Fu, Q.; Shi, R.; Tang, Y.; Long, Y. T.; He, X. P.; Jin, Y.; Liu, G.; Chen, G. R.; Chen, K. ‘Pungent’ Copper Surface Resists Acid Corrosion in Strong HCl Solutions. Ind. Eng. Chem. Res. 2014, 53, 64− 69. (12) Dafali, A.; Hammouti, B.; Mokhlisse, R.; Kertit, S. Substituted uracils as corrosion inhibitors for copper in 3% NaCl solution. Corros. Sci. 2003, 45, 1619−1630. (13) Huynh, N.; Bottle, S. E.; Notoya, T.; Trueman, A.; Hinton, B.; Schweinsberg, D. P. Studies on alkyl esters of carboxybenzotriazole as inhibitors for copper corrosion. Corros. Sci. 2002, 44, 1257−1276. (14) El Issami, S.; Bazzi, L.; Hilali, M.; Saloghi, R.; Kertit, S. Inhibition de la corrosion du cuivre en milieu HCl 0.5 M par les composes organiques de type triazole. Ann. Chim. 2002, 27, 63−72. (15) Subramanian, R.; Lakshminarayanan, V. Effect of adsorption of some azoles on copper passivation in alkaline medium. Corros. Sci. 2002, 44, 535−554. (16) Stupnisek-Lisac, E.; Brnada, A.; Mance, A. D. Secondary amines as copper corrosion inhibitors in acid media. Corros. Sci. 2000, 42, 243−257. (17) Matos, J. B.; Pereira, L. P.; Agostinho, S. M. L.; Cordeiro, G. G. O.; D’elia, E. Effect of cysteine on the anodic dissolution of copper in sulfuric acid medium. J. Electroanal. Chem. 2004, 570, 91−94. (18) Ehteshamzadeh, M.; Shahrabi, T.; Hosseini, M. Innovation in acid pickling treatments of copper by characterizations of a new series of Schiff bases as corrosion inhibitors. Anti-Corros. Methods Mater. 2006, 53, 296−302.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.iecr.5b02988. Characterization (including 1H-NMR, infrared spectrum, and elemental analysis) of C1−C9. Polarization curves and Nyquist plots for copper and C1−C9, variations of weight loss (a) and pH (b) with time for copper and C1−C9, Langmuir adsorption isotherm of C5 on the surface of copper (Figures S1−S4), polarization parameters for copper and C1−C9, and electrochemical parameters calculated from EIS measurements for copper and C1−C9 (Tables S1 and S2) (PDF)

■

■

The authors greatly thank the National Natural Science Foundation of China (no. 21376282) for their warm support. H.L. is grateful to the China Postdoctoral Science Foundation for financial support (Grant Nos. 22012T50762 and 2011M501388). We also appreciate the financial support from Municipal Natural Science Foundation of Chongqing (Grant Nos. CSTC2012jjB50007 and CSTC2010BB0216).

4. CONCLUSIONS To summarize, this study presents a range of new benzotriazole derivatives containing carbon chains as the corrosion inhibitors for copper in a 3.5 wt % NaCl solution based on rational molecular preconstruction. The polar head and the hydrophobic tail in the target inhibitors play significant roles in the corrosion inhibition. In particular, the carbon chain length attached to the molecular backbone is demonstrated to be greatly related to the corrosion inhibition efficiencies of the target inhibitors. The corrosion inhibition efficiencies determined by the polarization curves, EIS, and the weight loss experiments respectively show that the inhibitor C5 with a 7carbon chain exhibits the best corrosion inhibition efficiency ∼98% at 0.15 mM, while even the poorest inhibitor C1 can reach ∼60% inhibition efficiency. The electrochemical determination suggests that these new inhibitors act as mixed-type corrosion inhibitors, which display inhibition in the anodic and cathodic processes of the corrosion reactions through the formation of a protective layer on the copper surface and the adsorbed layer over the copper surface could be seen by SEM analysis. The adsorption of the inhibitors on copper is found to follow Langmuir isotherm, and the inhibitors show the adsorption of the mixed chemical and physical phenomena on the copper surface based on analysis of the values of ΔG0ads obtained. The quantum chemical calculation shows that these inhibitors adsorb as the molecular species using trinitrogen cycle and nitrogen and π electrons of the aromatic rings as the active centers and using carbon chains as the protection layer. The chemical bonding of aromatic polar heads of the inhibitors with the Cu atom ensures strong adsorption on the copper surface. The results presented herein greatly guide us to prepare neat corrosion inhibitors for copper in a sodium chloride medium.

■

Article

AUTHOR INFORMATION

Corresponding Authors

*Tel./Fax: 86-23-65102531. E-mail: [email protected] (F.G.). *E-mail: [email protected] (S.Z.). *E-mail: [email protected] (H.L.). Notes

The authors declare no competing financial interest. 12252


Article


(40) Sherif, E. M.; Ahmed, A. H. Synthesizing New Hydrazone Derivatives and Studying their Effects on the Inhibition of Copper Corrosion in Sodium Chloride Solutions. Synth. React. Inorg. Met.-Org. Chem. 2010, 40, 365−372. (41) Yan, C. W.; Lin, H. C.; Cao, C. N. Investigation of inhibition of 2-mercaptobenzoxazole for copper corrosion. Electrochim. Acta 2000, 45, 2815−2821. (42) Yurt, A.; Ulutas, S.; Dal, H. Electrochemical and theoretical investigation on the corrosion of aluminium in acidic solution containing some Schiff bases. Appl. Surf. Sci. 2006, 253, 919−925. (43) El-Awady, A. A.; Abd-El-Nabey, B. A.; Aziz, S. G. Kineticthermodynamic and adsorption isotherms analyses for the inhibition of the acid corrosion of steel by cyclic and open-chain amines. J. Electrochem. Soc. 1992, 139, 2149−2154. (44) Rudresh, H. B.; Mayanna, S. M. Adsorption of n-Decylamine on Zinc from Acidic Chloride Solution. J. Electrochem. Soc. 1977, 124, 340−342. (45) Bentiss, F.; Lebrini, M.; Lagrenée, M.; Traisnel, M.; Elfarouk, A.; Vezin, H. The influence of some new 2,5-disubstituted 1,3,4thiadiazoles on the corrosion behaviour of mild steel in 1M HCl solution: AC impedance study and theoretical approach. Electrochim. Acta 2007, 52, 6865−6872. (46) Hegazy, M. A.; Badawi, A. M.; El Rehim, S. S. A.; Kamel, W. M. Corrosion inhibition of carbon steel using novel N-(2-(2mercaptoacetoxy)ethyl)-N, N-dimethyl dodecan-1-aminium bromide during acid pickling. Corros. Sci. 2013, 69, 110−122. (47) Matsumoto, F.; Ozaki, M.; Inatomi, Y.; Paulson, S. C.; Oyama, N. Studies on the Adsorption Behavior of 2,5-Dimercapto-1,3,4thiadiazole and 2-Mercapto-5-methyl-1,3,4-thiadiazole at Gold and Copper Electrode Surfaces. Langmuir 1999, 15, 857−865. (48) Piet, D. P.; Danovich, D.; Zuilhof, H.; Sudhölter, E. J. R. Ionization potentials of porphyrins and phthalocyanines. A comparative benchmark study of fast improvements of Koopman’s Theorem. J. Chem. Soc., Perkin Trans. 2 1999, 2, 1653−1661. (49) Pearson, R. G. Absolute electronegativity and hardness. Inorg. Chem. 1988, 27, 734−740.

(19) Zhao, Y. S.; Yang, W.; Zhang, G.; Ma, Y.; Yao, J. A hierarchical self-assembly of 4, 5-diphenylimidazole on copper. Colloids Surf., A 2006, 277, 111−118. (20) Huynh, N.; Bottle, S. E.; Notoya, T.; Schweinsberg, D. P. Inhibition of copper corrosion by coatings of alkyl esters of carboxybenzotriazole. Corros. Sci. 2002, 44, 2583−2596. (21) Brunoro, G.; Frignani, A.; Colledan, A.; Chiavari, C. Organic films for protection of copper and bronze against acid rain corrosion. Corros. Sci. 2003, 45, 2219−2231. (22) Lusk, A. T.; Jennings, G. K. Characterization of self-assembled monolayers formed from sodium S-alkyl thiosulfates on copper. Langmuir 2001, 17, 7830−7836. (23) Zhang, D. Q.; Gao, L. X.; Zhou, G. D.; Lee, K. Y. Undecyl substitution in imidazole and its action on corrosion inhibition of copper in aerated acidic chloride media. J. Appl. Electrochem. 2007, 38, 71−76. (24) Abrahamsson, S.; Dahlén, B.; Löfgren, H.; Pascher, I.; Sundell, S. Molecular Arrangement and Conformation of Lipids of Relevance to Membrane Structure. Struct. Biol. Membr. 1977, 34, 1−23. (25) Lu, Y.; Gong, Y. L.; Ma, H. Y.; Wang, Z. Q.; Li, H. L.; Luo, Z. P.; Li, H. R.; Gao, F. 4-Formyl-2-(2H-benzotriazol-2-yl)-phenol: an ESIPT chromophore. Chin. Sci. Bull. 2014, 59, 4741−4751. (26) Qin, T. T.; Li, J.; Luo, H. Q.; Li, M.; Li, N. B. Corrosion inhibition of copper by 2,5-dimercapto-1,3,4-thiadiazole monolayer in acidic solution. Corros. Sci. 2011, 53, 1072−1078. (27) Satapathy, A. K.; Gunasekaran, G.; Sahoo, S. C.; Amit, K.; Rodrigues, P. V. Corrosion inhibition by Justicia gendarussa plant extract in hydrochloric acid solution. Corros. Sci. 2009, 51, 2848−2856. (28) Guo, W. J.; Chen, S. H.; Houyi, M.A. A study of the inhibition of copper corrosion by triethyl phosphate and triphenyl phosphate self-assembled monolayers. J. Serb. Chem. Soc. 2006, 71, 167−175. (29) Guo, W. J.; Chen, S. H.; Ma, H. Y. A study of the inhibition of copper corrosion by triethyl phosphate and triphenyl phosphate selfassembled monolayers. J. Serb. Chem. Soc. 2006, 71, 167−175. (30) Tao, Z.; Zhang, S.; Li, W.; Hou, B. Corrosion inhibition of mild steel in acidic solution by some oxo-triazole derivatives. Corros. Sci. 2009, 51, 2588−2595. (31) Rao, B. V. A.; Iqbal, M. Y.; Sreedhar, B. Self-assembled monolayer of 2-(octadecylthio)benzothiazole for corrosion protection of copper. Corros. Sci. 2009, 51, 1441−1452. (32) Sherif, E. M.; Park, S. M. Inhibition of Copper Corrosion in 3.0% NaCl Solution by N-Phenyl-1,4-phenylenediamine. J. Electrochem. Soc. 2005, 152, 428−433. (33) Lamaka, S. V.; Zheludkevich, M. L.; Yasakau, K. A.; Serra, R.; Poznyak, S. K.; Ferreira, M. G. S. Nanoporous titania interlayer as reservoir of corrosion inhibitors for coatings with self-healing ability. Prog. Org. Coat. 2007, 58, 127−135. (34) Sherif, E. M.; Erasmus, R. M.; Comins, J. D. Inhibition of copper corrosion in acidic chloride pickling solutions by 5-(3-aminophenyl)tetrazole as a corrosion inhibitor. Corros. Sci. 2008, 50, 3439−3445. (35) Hong, S.; Chen, W.; Luo, H. Q.; Li, N. B. Inhibition effect of 4amino-antipyrine on the corrosion of copper in 3 wt.% NaCl solution. Corros. Sci. 2012, 57, 270−278. (36) Li, W.; He, Q.; Pei, C.; Hou, B. Experimental and theoretical investigation of the adsorption behaviour of new triazole derivatives as inhibitors for mild steel corrosion in acid media. Electrochim. Acta 2007, 52, 6386−6394. (37) Hassan, H. H. Perchlorate and oxygen reduction during Zn corrosion in a neutral medium. Electrochim. Acta 2006, 51, 5966− 5972. (38) Rochdi, A.; Kassou, O.; Dkhireche, N.; Touir, R.; El Bakri, M.; Ebn Touhami, M.; Sfaira, M.; Mernari, B.; Hammouti, B. Inhibitive properties of 2,5-bis(n-methylphenyl)-1,3,4-oxadiazole and biocide on corrosion, biocorrosion and scaling controls of brass in simulated cooling water. Corros. Sci. 2014, 80, 442−452. (39) Tao, Z.; He, W.; Wang, S.; Zhang, S.; Zhou, G. A study of differential polarization curves and thermodynamic properties for mild steel in acidic solution with nitrophenyltriazole derivative. Corros. Sci. 2012, 60, 205−213. 12253


Synthesis of New Benzotriazole Derivatives Containing Carbon

Recommend Documents