The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study

JMRTEC-1064; No. of Pages 10

ARTICLE IN PRESS j m a t e r r e s t e c h n o l . 2 0 1 9;x x x(x x):xxx–xxx

Available online at www.sciencedirect.com

www.jmrt.com.br

Original Article

The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study Yangyang Feng b , Li Feng b , Yuling Sun a , Jiahong He a,∗ a b

School of Materials and Chemical Engineering, Chongqing University of Arts and Sciences, Yongchuan 402160, China College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, China

a r t i c l e

i n f o

a b s t r a c t

Article history:

The 3,3 -((4-(methylthio)phenyl)methylene)bis(1H-indole) (TPBI) of indole derivative was

Received 24 June 2019

synthesized through the reaction of indole (ID) with 4-(methylthio)benzaldehyde. The

Accepted 31 October 2019

electrochemical investigation showed that TBPI served as mixed-type inhibitor to protect

Available online xxx

copper against corrosion more efficiently than ID, which was further demonstrated by comprehensive characterizations. The efficient inhibitive performance was attributed to the

Keywords:

self-assembled monolayers (SAMs) on the copper surface formed by the interaction of N

Copper corrosion

and S atoms of TPBI with copper (I). Quantum calculations results further confirmed that

Indole derivative

the inhibitory effect of TPBI was better than ID.

Self-assembled monolayers Electrochemical experiments

© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Quantum calculations

1.

Introduction

Copper is one of the most widely applied metals in industry due to its high electrical and thermal conductivity [1–3]. However, impacted by the acid rain during the process of using, it was easy to form oxidized corrosion products on the surface of copper equipment, which caused a sharp drop in electrical conduction and heat transfer efficiencies of the equipment [4]. Therefore, pickling solutions, such as sulfuric acid, were often used to remove corrosion products from the surface of copper [5]. Unfortunately, sulfuric acid could also corrode copper. As a result, studies on the protection of copper against corrosion in

∗

acidic media have attracted much attention. One of the most effective strategies to prevent copper from corrosion in acidic environment was the use of organics as corrosion inhibitors [6–8]. Among these organic inhibitors, N and S atoms were often present, since they could easily chelate with copper surface to form self-assembled monolayers (SAMs), which were used as insulating layers to prevent the penetration of corrosive species [9–14]. In addition, the corrosion effect was improved when increasing the number of heterocyclic rings in organics. For instance, Gao and co-workers described that the increasing of number of N-heterocycles had a positive effect on anticorrosion performance of copper in seawater [2,15]. Indole is a class of readily available and less-toxic organic compound. In addition, the N-heterocycle in the indole skeleton could provide adsorption center to interact with copper surface. Carboxyl or chlorine substituted indoles have been

Corresponding author. E-mail: [email protected] (J. He). https://doi.org/10.1016/j.jmrt.2019.10.087 2238-7854/© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: Feng Y, et al. The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study. J Mater Res Technol. 2019. https://doi.org/10.1016/j.jmrt.2019.10.087

JMRTEC-1064; No. of Pages 10

2

ARTICLE IN PRESS j m a t e r r e s t e c h n o l . 2 0 1 9;x x x(x x):xxx–xxx

2.3.

Scheme 1 – Synthesis of TPBI.

disclosed as corrosion inhibitors [16,17]. However, the corrosion inhibition effect of indole with one N-heterocyclic ring was far from satisfactory. Hence, we envisaged increasing the number of heterocyclic rings in indole derivative to improve the corrosion inhibition effect. In this work, we firstly designed a new indole derivative (TPBI) bearing two N-heterocyclic rings. Then, the anticorrosion ability of TPBI and ID for copper in 0.5 M H2 SO4 solution were studied by electrochemical experiments. The adsorption mechanism of TPBI was investigated by surface characterizations (FT-IR, XPS, SEM-EDS, and CA) and quantum calculations. These results revealed that increasing the number of heterocyclic rings in indole molecule had a significant effect on anticorrosion ability, and provided a new direction for designing new indole-based corrosion inhibitors.

2.

Experiments

2.1.

Synthesis and characterization of target molecule

TPBI was synthesized through a convenient and effective method as shown in Scheme 1. 4-(Methylthio)benzaldehyde (5 mmol), indole (10 mmol), ether (10 mL), BF3 -Et2 O (0.01 mmol) were added into a dry round bottom flask successively. The reaction mixture was stirred at room temperature for 2 h. After the reaction was completed, the reaction solvent was removed under vacuum and purified by silica gel column chromatography using ethyl acetate/petroleum ether (1/8, v/v) as the eluent to give the pure product as yellow solid in 85% yield. The synthesized TPBI was characterized by 1 H NMR and 13 C NMR analysis in Figure S1 and S2.

Preparation of solution and self-assembled 2.2. protective film TPBI or ID was dissolved in ethanol to prepared different concentrations of solution. The copper specimens were meticulously ground with a variety of emery papers (400, 800, 1200, 2000 grits) to get a smooth surface, then washed with ultrapure water and ethanol continuously to remove all contaminants, finally, dried under a stream of nitrogen. After that, the prepared specimens were immersed in 10 mM inhibitor solutions for various time (1, 4, 8, 12 h) at 298 K. In addition, copper specimens were immersed in different concentrations of TPBI solution (1, 3, 6, 10 mM) for 12 h.

Electrochemical measurement

The electrochemical measurements were performed in threeelectrode system. A modified copper sample acted as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum plate as the counter electrode. Electrochemical impedance spectroscopy (EIS) was determined in the frequency range from 100 kHz to 0.01 Hz under the open-circuit potential (OCP) in a stable state. And the impedance parameters were fitted and analyzed by Zsimpwin software. The polarization curves were tested from −300 mV to +200 mV (versus OCP) at 1 mV s−1 potential scanning rate. The corrosion inhibition efficiencies () were calculated from polarization curves and EIS according to the following equations [18,19]: P =

jcorr − jcorr,0 × 100 jcorr,0

(1)

E =

Rct − Rct,0 × 100 Rct

(2)

Herein, jcorr ,0 and jcorr were the corrosion current densities without and with the inhibitors, Rct,0 and Rct were the charge transfer resistances of copper electrodes without and with inhibitors, respectively.

2.4.

Surface characterizations

Fourier transform infrared (FT-IR), energy-dispersive spectroscope (EDS) and X-ray photoelectron spectroscopy (XPS) were employed to investigate the adsorption mechanism of TPBI molecule self-assembled on copper surface. XPS measurement was carried on a PHI 5700 spectrometer with Al Ka anode (1486.6 eV). The surface wet ability was measured by contact angle (CA) under static. The surface morphology of the studied copper specimen was measured by scanning electron microscope (SEM) under high vacuum.

2.5.

Theoretical calculation research

The software of the molecular dynamic simulation (Material Studio 7.0, Accelrys Inc.) was employed to research the quantum chemical calculations. The structures were optimized using the density functional theory (DFT).

3.

Results and discussion

3.1.

Optimum conditions for formation of the SAMs

3.1.1.

Effect of self-assembly time

Polarization curves of the copper specimens measured in 0.5 M H2 SO4 solution after immersion in 10 mM inhibitor solutions for various self-assembly time were revealed in Fig. 1. The polarization branches were extrapolated up to their point of intersection to acquire the corrosion current density (jcorr ) and corrosion potential (Ecorr ) in Table S1 [20]. It was worth noting that the Ecorr value of modified copper shifted toward to the negative direction slightly relative to the

Please cite this article in press as: Feng Y, et al. The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study. J Mater Res Technol. 2019. https://doi.org/10.1016/j.jmrt.2019.10.087

JMRTEC-1064; No. of Pages 10

ARTICLE IN PRESS j m a t e r r e s t e c h n o l . 2 0 1 9;x x x(x x):xxx–xxx

3

Fig. 1 – Polarization curves of the copper specimens measured in 0.5 M H2 SO4 solution after immersion in 10 mM ID (a) or TPBI (b) solutions for various self-assembly time.

blank in Fig. 1. Meanwhile, the current density of modified copper decreased as compared with blank in the same condition. It was obvious that TPBI molecule (91.61%, 1 h) exhibited better corrosion inhibition efficiency than ID (54.75%, 1 h) under the same experimental condition as shown in Table S1. This indicated that the new TPBI inhibitor could form a more compact protective film on copper surface than ID. In addition, the maximum negative shift values of Ecorr for TPBI and ID were 73 mV and 48 mV, respectively. The results indicated displacements were lower than 85 mV. Hence, TPBI and ID acted as mixed-type inhibitors [21]. The Nyquist plots of the copper specimens measured in 0.5 M H2 SO4 solution after immersion in 10 mM inhibitor solutions for various self-assembly time were presented in Fig. 2. The symbols and the straight lines in all Nyquist plots were raw testing data and fitting data, respectively. Fig. 2(a) presented a depress semicircle in high frequencies with a straight line in low frequencies. And the straight line was attributed to Warburg impedance, which was caused by the transportation of dissolved oxygen and corrosion media to the copper surface [22]. In contrast, Fig. 2(b) showed a capacitive loop without a straight line, implying that TPBI inhibitor strongly prevented the diffusion process and the corrosion of copper was controlled by a charge transfer process. However, the capacitive loops were not perfect, probably because of the roughness and inhomogeneity of the copper electrodes [23]. Furthermore, the diameters of the curves were significantly increased along with the extending of self-assemble time. The equivalent circuits were chosen to analyze the Nyquist plots in Fig. 3. The impedance of CPE was described as the followings [24,25]:

ZCPE =

1 Y(jω)

n

(3)

where Y was the admittance of the electrochemical system, j was the imaginary root, ω was for the angular frequency, and n showed the deviation parameter. The value of n typically ranged from −1 to 1. When n = −1, the CPE represented for an inductor, if n = 0, the CPE represented a pure resistor, if n = 0.5, the CPE represented the Warburg impedance, and if n = 1, the CPE represented a pure capacitor [21].

Table S2 presented the impedance parameters derived from the equivalent circuits. The Rct value of copper modified with TPBI (98.72%, 8 h) was distinctly higher than modified with ID (79.33%, 8 h), suggesting that TPBI was able to efficiently inhibit copper corrosion compared with ID. It was worth noting that when copper electrode was immersed in TPBI ethanol solution for 1 h and 12 h, the E % values were 92.96% and 99.10%, respectively. These results indicated that the process of forming TPBI-SAMs was a fast adsorption and then a slow rearrangement [8].

3.1.2.

Effect of TPBI concentration

Electrochemical experiments were conducted to further explore whether the inhibition efficiency was affected by the concentration of TPBI solution. The results were showed in Tafel curves (a), Nyquist (b), Impedance (c), and Phase angle (d) images (Fig. 4). Clearly, the Ecorr value of modified copper shifted toward to the negative direction slightly relative to blank in Fig. 4(a). And the polarization curves shifted to low current densities with increase of the concentrations of TPBI and reached the minimal value at 10 mM. However, the current density showed an increase at 12 mM relative to that at 10 mM. This phenomenon may be due to that the amounts of adsorbed inhibitor molecules reached a critical value and rearranged on the substrate [2], so that corrosive sulfate ions could easily attack copper electrode through the interspaces. Fig. 4(b) suggested that the diameter of capacitive loop increased with increasing the concentration of TPBI and reached maximum at 10 mM. The impedance plot (Fig. 4(c)) indicated that the copper specimens modified with TPBI showed high impedance values relative to blank. Additionally, it was found that the low-frequency impedance nearly increased two orders of magnitude compared with blank, suggesting that TPBI had good corrosion resistance. The phase angle plot in Fig. 4(d) showed the maximal phase angle became bigger with the increasing concentrations of TPBI and reached the maximal value at 10 mM. These results indicated that appropriate increased concentration of TPBI solution could form a more stable and dense protective film on copper electrode. Tables S3 and S4 showed polarization curves and impedance parameters of TPBI, respectively.

Please cite this article in press as: Feng Y, et al. The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study. J Mater Res Technol. 2019. https://doi.org/10.1016/j.jmrt.2019.10.087

JMRTEC-1064; No. of Pages 10

4

ARTICLE IN PRESS j m a t e r r e s t e c h n o l . 2 0 1 9;x x x(x x):xxx–xxx

Fig. 2 – Nyquist plots of the copper specimens measured in 0.5 M H2 SO4 solution after immersion in 10 mM ID (a) or TPBI (b) solutions for various self-assembly time.

Fig. 3 – Equivalent circuit models fitting the EIS experimental data.

Fig. 4 – Tafel curve (a), Nyquist (b), Impedance (c), and Phase angle (d) images of copper measured in 0.5 M H2 SO4 solution after immersion in different concentration solution of TPBI for 12 h.

3.2.

FT-IR analysis

The synthesized TPBI compound and the TPBI-SAMs on the copper substrate were studied by FT-IR and ATR-IR, respectively. The broad band at 3409.5 cm−1 was attributed to the

v(N–H) [26], and the peak at around 3000 cm−1 was assigned to H2 O and vibration of C–H in phenyl ring [27] in Fig. 5. The stretching bands at 1456.4 cm−1 and 741.7 cm−1 corresponded to the C–N bond [28] and C–S bond [8,29], respectively. It was interesting that the peaks at 3409.5 cm−1 , 1456.4 cm−1 , and

Please cite this article in press as: Feng Y, et al. The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study. J Mater Res Technol. 2019. https://doi.org/10.1016/j.jmrt.2019.10.087

JMRTEC-1064; No. of Pages 10

ARTICLE IN PRESS j m a t e r r e s t e c h n o l . 2 0 1 9;x x x(x x):xxx–xxx

5

followings) was attributed to carbon contamination. As compared with bare copper, some new peaks such as S2s, S2p, and N1s were presented in the XPS spectroscopy of copper surface covered with TPBI (referred to as Cu-TPBI in the followings). These results indicated that TPBI molecule adsorbed on the copper surface successfully.

3.3.1. XPS spectra of Cu 2p from the studied copper specimen surfaces

Fig. 5 – FT-IR and ATR-IR spectra of pure TPBI powder (a) and TPBI-SAMs (b).

XPS spectra of Cu2p from the copper surfaces covered without and with TPBI immersed in 0.5 M H2 SO4 solution for 12 h were presented in Fig. 7. The high-resolution spectra of Cu2p showed similar peak shapes and binding energies (Cu2p1/2 , 951.90 eV for bare copper, 952.35 eV for Cu-TPBI; Cu2p3/2 , 932.05 eV for bare copper, 932.50 eV for Cu-TPBI) that could be related to Cu (I) [15]. No satellite peaks were found between typical Cu2p1/2 and Cu2p3/2 in Cu2p spectra, which suggested that the inexistence of Cu (II) in the copper sample surfaces [2]. As discussed above the copper only transferred from Cu (0) to Cu (I) in the process of copper corrosion.

3.3.2. XPS spectra of C1s from the studied copper specimen surfaces

Fig. 6 – The XPS survey spectra of the copper surfaces covered without and with TPBI immersed in 0.5 M H2 SO4 solution for 12 h.

741.7 cm−1 displayed a dramatical reduction, implying that TPBI molecule adsorbed on copper surface through chemical complexation of N and S atoms with copper ions.

3.3.

XPS for TPBI-SAMs

XPS measurement was carried to explore the adsorption mechanism of TPBI molecule self-assembled on copper surface. And the peaks of different elements on copper surfaces were detected after the copper specimens were covered without and with inhibitor immersed in 0.5 M H2 SO4 solution for 12 h. Fig. 6 presented the XPS survey spectra of the copper surfaces covered without and with TPBI immersed in 0.5 M H2 SO4 solution for 12 h. The presence of C and O in the copper surface covered without inhibitor (referred to as Cu-bare in the

Fig. 8 showed de-convolution spectra of the C1s for the copper surfaces covered without and with TPBI immersed in 0.5 M H2 SO4 solution for 12 h. The corresponding chemical states, full width at half maximum (FWHM), and binding energy were shown in Table S5. As shown in Fig. 8(a), C1s spectroscopy of surface from Cu-bare could be resolved into C–C, C–O, and O–C O components which were located at 284.82, 286.20, and 288.35 eV as the result of adventitious carbon contamination [30,31]. The peak centered at 284.80 eV corresponded to the calibrated carbon, and C1s spectroscopy of surface from Cu-TPBI could be assigned to C–C/C C (284.72 eV), C–S (285.53 eV), C–O (286.86 eV), and C–N/O–C O (288.40 eV) as shown in Fig. 8(b) [32–35], indicating that the carbon contamination also existed in copper surface covered with TPBI. As compared with bare copper surface, C–S and C–N bonds were detected on copper surface covered with TPBI, demonstrating that the inhibitor adsorbed on copper surface successfully.

3.3.3. XPS spectra of N1s and S2p from the studied copper specimen surfaces De-convolutions of N1s and S2p spectra for the investigated copper sample surface covered with TPBI immersed in 0.5 M H2 SO4 solution for 12 h were showed in Fig. 9(a) and (b), respectively. The corresponding chemical states, FWHM, and binding energy were shown in Tables S6 and S7. The surveyed spectroscopy of N1s from Cu-TPBI presented mainly two peaks. The peak centered at 399.09 eV related to the bond of N–Cu produced by nitrogen atom with Cu (I) [36]. In addition, the peak at higher binding energy (400.38 eV) was corresponded to the bond of N–H in TPBI molecule structure [37]. Fig. 9(b) described the S2p spectroscopy of Cu-TPBI. It was obvious that two peaks at 163.20 eV and 164.39 eV were detected due to the existence of S–Cu bond [38,39]. Therefore, these results revealed that both N and S atoms combined with Cu (I) leading to the chemical adsorption, which was in keeping with FT-IR measurements.

Please cite this article in press as: Feng Y, et al. The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study. J Mater Res Technol. 2019. https://doi.org/10.1016/j.jmrt.2019.10.087

JMRTEC-1064; No. of Pages 10

6

ARTICLE IN PRESS j m a t e r r e s t e c h n o l . 2 0 1 9;x x x(x x):xxx–xxx

Fig. 7 – Cu2p XPS spectra of the copper surfaces covered without (a) and with TPBI (b) immersed in 0.5 M H2 SO4 solution for 12 h.

Fig. 8 – C1s XPS spectra of the copper surfaces covered without (a) and with TPBI (b) immersed in 0.5 M H2 SO4 solution for 12 h.

Fig. 9 – XPS high-resolution spectra of N1s (a), S2p (b) from copper surface covered with TPBI immersed in 0.5 M H2 SO4 solution for 12 h.

3.4.

Contact angle analysis of copper surfaces

The contact angle measurement was applied to explore the wet ability of the studied copper specimens. The contact angle values of the surfaces from polished copper and copper modified with TPBI were 70.5◦ and 100.6◦ , respectively (Fig. 10). It was known that hydrophobic structure was better able to isolate air and prevent copper substrate from contacting corrosive media [40]. So, the copper surface modified with TPBI

presented a good hydrophobicity. These results indicated that TPBI structure had a good hydrophobicity.

3.5.

SEM and EDS analysis of copper surfaces

SEM and EDS measurements were employed to study the copper surfaces before or after immersion in 0.5 M H2 SO4 solution for 12 h in Fig. 11. The polished copper presented a smooth and tidy metal surface (Fig. 11(a)), but the polished copper

Please cite this article in press as: Feng Y, et al. The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study. J Mater Res Technol. 2019. https://doi.org/10.1016/j.jmrt.2019.10.087

JMRTEC-1064; No. of Pages 10

ARTICLE IN PRESS j m a t e r r e s t e c h n o l . 2 0 1 9;x x x(x x):xxx–xxx

7

Fig. 10 – The images of contact angle from surfaces of polished copper (a), copper covered with TPBI (b).

Fig. 11 – SEM and EDS images of surfaces from polished copper (a and e), polished copper immersed in 0.5 M H2 SO4 solution for 12 h (b and e), and copper covered with TPBI inhibitor immersed in 0.5 M H2 SO4 solution for 12 h (c and f).

immersed in 0.5 M H2 SO4 solution for 12 h exhibited a porous and rough surface due to the attack of sulfate ions (Fig. 11(b)). It was obvious that the protective layer of TPBI completely covered the copper surface in form of spherical adsorption layer (Fig. 11(c)). Meanwhile, the new peaks of N and S atoms were found in EDS image (Fig. 11(f)) as compared with the polished copper (Fig. 11(d)). These results demonstrated that TPBI

adsorbed on the copper surface to form the protective layer, which was agreement with electrochemical experiments.

3.6.

Adsorption isotherm

The adsorption mechanism of the inhibitor self-assembled on the copper surface was further studied by adsorption isotherm

Please cite this article in press as: Feng Y, et al. The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study. J Mater Res Technol. 2019. https://doi.org/10.1016/j.jmrt.2019.10.087

JMRTEC-1064; No. of Pages 10

8

ARTICLE IN PRESS j m a t e r r e s t e c h n o l . 2 0 1 9;x x x(x x):xxx–xxx

Thermodynamic parameters of the TPBI inhibitor were obtained from Langmuir adsorption isotherm in Table S8. A high value of K and a low value of G◦ suggested that the TPBI inhibitor could firmly adsorbed on copper surface. The calculated value of G◦ was between −40 kJ/mol and −20 kJ/mol, implying that the adsorption of TPBI on copper surface was attributed to both physisorption and chemisorption.

3.7.

Fig. 12 – Langmuir adsorption isotherm of TPBI on copper surfaces in 0.5 M H2 SO4 solution.

which was derived by fitting surface coverage () as a function of the TPBI concentration. Langmuir’s adsorption isotherm was obtained using the following formula [41]:  =K×C 1−

(4)

wherein K showed the equilibrium constant of the adsorption, and c represented the concentration of the TPBI solution. The K was linked to the energy of adsorption (G◦ ) using the relation [42,43]: K=

 1  55.5

 G◦ 

exp −

RT

(5)

where R was the universal gas constant, and T was the absolute temperature. The plot of Langmuir isotherm yielded using linear regression of c/ versus c exhibited in Fig. 12. The linear regression coefficient was very close to 1 (RP2 = 0.998), which indicated that the adsorption of inhibitors at the copper-solution interface abided by Langmuir isotherm.

Theoretical calculation

The quantum calculation results of the two molecules were shown in Fig. 13. The HOMO and LUMO orbitals of ID were mainly concentrated on the entire molecular plane, indicating that the entire molecular plane was the reactive site of the molecule. TPBI had more active sites than ID, because it was distributed on the indole molecule, the benzene ring and the S atom. This also indicated that the TPBI easily and strongly adsorbed on the copper surface to form a passivation film. As seen in Table S9, TPBI showed a higher value of EHOMO , which suggested it easily offered electrons [30]. In addition, the smaller energy difference (E) and the larger dipole moment () represented stronger reactivity [44], so the corrosion inhibition effect would be: TPBI > ID. Theoretical calculations provided a better basis for corrosion inhibition mechanisms and experimental conclusions.

4.

Conclusion

In summary, a new indole derivative was synthesized through a concise method. The inhibition efficiency of TPBI was studied by electrochemical measurements, which indicated that TPBI as mixed-type inhibitor was able to efficiently inhibit copper corrosion compared with ID. FT-IR, EDS, XPS and CA measurements demonstrated that N and S atoms of TPBI interacted with copper surface to form a dense protective film. Additionally, the adsorption of TPBI on copper surface was attributed to both physisorption and chemisorption and abided by Langmuir isotherm. The theoretical calculations agreed with the experimental results. These systematic stud-

Fig. 13 – Molecular frontier orbital maps of ID and TPBI. Please cite this article in press as: Feng Y, et al. The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study. J Mater Res Technol. 2019. https://doi.org/10.1016/j.jmrt.2019.10.087

JMRTEC-1064; No. of Pages 10

ARTICLE IN PRESS j m a t e r r e s t e c h n o l . 2 0 1 9;x x x(x x):xxx–xxx

ies provided a new direction for designing new indole-based corrosion inhibitors. [10]

Conflict of interest We have no conflicts of interest to this work. We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

[11]

Acknowledgement

[12]

This work was supported by the Municipal Natural Science Foundation of Chongqing (cstc2015jcyjA1403, cstc2017jcyjAX0309, cstc2018jcyjAX0313).

[13]

Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at https://doi.org/10. 1016/j.jmrt.2019.10.087.

references

[1] Tian H, Li W, Cao K, Hou B. Potent inhibition of copper corrosion in neutral chloride media by novel non-toxic thiadiazole derivatives. Corros Sci 2013;73:281–91, http://dx.doi.org/10.1016/j.corsci.2013.04.017. [2] Huang HJ, Wang ZQ, Gong YL, Gao F, Luo ZP, Zhang ST, et al. Water soluble corrosion inhibitors for copper in 3.5 wt% sodium chloride solution. Corros Sci 2017;123:339–50, http://dx.doi.org/10.1016/j.corsci.2017.05.009. [3] Yu HJ, Li CX, Yuan BY, Li L, Wang C. The inhibitive effects of AC-treated mixed self-assembled monolayers on copper corrosion. Corros Sci 2017;120:231–8, http://dx.doi.org/10.1016/j.corsci.2017.03.006. [4] Huang HJ, Fu Y, Wang XC, Guo YC, Wang ZQ, Zhang ST, et al. Nano- to micro-self-aggregates of new bisimidazole-based copoly(ionic liquid)s for protecting copper in aqueous sulfuric acid solution. ACS Appl Mater Interface 2019;11:10135–45, http://dx.doi.org/10.1021/acsami.8b19993. [5] Tan BC, Zhang ST, Li WP, Zou XL, Qiang YJ, Xu LH, et al. Experimental and theoretical studies on inhibition performance of Cu corrosion in 0.5 M H2 SO4 by three disulfide derivatives. J Ind Eng Chem 2019;77:449–60, http://dx.doi.org/10.1016/j.jiec.2019.05.01. [6] Loto RT. Corrosion inhibition effect of non-toxic ␣-amino acid compound on high carbon steel in low molar concentration of hydrochloric acid. J Mater Res Technol 2019;8:484–93, http://dx.doi.org/10.1016/j.jmrt.2017.09.005. [7] Behpour M, Mohammadi N. Investigation of inhibition properties of aromatic thiol self-assembled monolayer for corrosion protection. Corros Sci 2012;65:331–9, http://dx.doi.org/10.1016/j.corsci.2012.08.036. [8] Rao BVA, Iqbal MY, Sreedhar B. Electrochemical and surface analytical studies of the self-assembled monolayer of 5-methoxy-2-(octadecylthio)benzimidazole in corrosion protection of copper. Electrochim Acta 2010;55:620–31, http://dx.doi.org/10.1016/j.electacta.2009.09.007. [9] Zhang J, Liu Z, Han GC, Chen SL, Chen ZC. Inhibition of copper corrosion by the formation of Schiff base

[14]

[15]

[16]

[17]

[18]

[19]

[20]

[21]

[22]

9

self-assembled monolayers. Appl Surf Sci 2016;389:601–8, http://dx.doi.org/10.1016/j.apsusc.2016.07.116. Guo WJ, Chen SH, Huang BD, Ma HY, Yang XG. Protection of self-assembled monolayers formed from triethyl phosphate and mixed self-assembled monolayers from triethyl phosphate and cetyltrimethyl ammonium bromide for copper against corrosion. Electrochim Acta 2006;52:108–13, http://dx.doi.org/10.1016/j.electacta.2006.03.089. Yang WJ, Li TQ, Zhou HH, Huang Z, Fu CP, Chen L, et al. Electrochemical and anti-corrosion properties of octadecanethiol and benzotriazole binary self-assembled monolayers on copper. Electrochim Acta 2016;220:245–51, http://dx.doi.org/10.1016/j.electacta.2016.10.123. Hu S, Chen ZY, Guo XP. Inhibition effect of three-dimensional (3D) nanostructures on the corrosion resistance of 1-dodecanethiol self-assembled monolayer on copper in NaCl solution. Materials 2018:11, http://dx.doi.org/10.3390/ma11071225. Wang YB, Liu Z, Li DY, Dong YP, Li W, Li N. The polymeric nanofilm of triazinedithiolsilane fabricated by self-assembled technique on copper surface. Part 1: Design route and corrosion resistance. Corros Sci 2015;98:382–90, http://dx.doi.org/10.1016/j.corsci.2015.05.054. Liu W, Xu QJ, Han J, Chen XH, Min YL. A novel combination approach for the preparation of superhydrophobic surface on copper and the consequent corrosion resistance. Corros Sci 2016;110:105–13, http://dx.doi.org/10.1016/j.corsci.2016.04.015. Wang ZQ, Gong YL, Zhang L, Jing C, Gao F, Zhang ST, et al. Self-assembly of new dendrimers basing on strong ␲–␲ intermolecule interaction for application to protect copper. Chem Eng J 2018;342:238–50, http://dx.doi.org/10.1016/j.cej.2018.02.080. Quartarone G, Battilana M, Bonaldo L, Tortato T. Investigation of the inhibition effect of indole-3-carboxylic acid on the copper corrosion in 0.5 M H2 SO4 . Corros Sci 2008;50:3467–74, http://dx.doi.org/10.1016/j.corsci.2008.09.032. Scendo M, Poddebniak D, Malyszko J. Indole and 5-chloroindole as inhibitors of anodic dissolution and mixed-type deposition of copper in acidic chloride solutions. J Appl Electrochem 2003;33:287–93, http://dx.doi.org/10.1023/A:1024117230591. Wang QH, Tan BC, Bao HB, Xie YT, Mou YX, Li PC, et al. Evaluation of ficus tikoua leaves extract as an eco-friendly corrosion inhibitor for carbon steel in HCl media. Bioelectrochemistry 2019;128:49–55, http://dx.doi.org/10.1016/j.bioelechem.2019.03.001. Liu JL, Cai JS, Shi L, Liu JZ, Zhou XC, Mu S, et al. The inhibition behavior of a water-soluble silane for reinforcing steel in 3.5% NaCl saturated Ca(OH)2 solution. Construct Build Mater 2018;189:95–101, http://dx.doi.org/10.1016/j.conbuildmat.2018.08.151. Luo XH, Ci CG, Li J, Lin KD, Du S, Zhang HX, et al. 4-Aminoazobenzene modified natural glucomannan as a green eco-friendly inhibitor for the mild steel in 0.5 M HCl solution. Corros Sci 2019;151:132–42, http://dx.doi.org/10.1016/j.corsci.2019.02.027. Tan BC, Zhang ST, Liu HY, Qiang YJ, Li WP, Guo L, et al. Insights into the inhibition mechanism of three 5-phenyltetrazole derivatives for copper corrosion in sulfuric acid medium via experimental and DFT methods. J Taiwan Inst Chem E 2019;102:424–37, http://dx.doi.org/10.1016/j.jtice.2019.06.005. Fan HQ, Li SY, Zhao ZC, Wang H, Shi ZC, Zhang L. Inhibition of brass corrosion in sodium chloride solutions by self-assembled silane films. Corros Sci 2011;53:4273–81, http://dx.doi.org/10.1016/j.corsci.2011.08.039.

Please cite this article in press as: Feng Y, et al. The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study. J Mater Res Technol. 2019. https://doi.org/10.1016/j.jmrt.2019.10.087

JMRTEC-1064; No. of Pages 10

10

ARTICLE IN PRESS j m a t e r r e s t e c h n o l . 2 0 1 9;x x x(x x):xxx–xxx

[23] Solomon MM, Gerengi H, Umoren SA. Carboxymethyl cellulose/silver nanoparticles composite: synthesis, characterization and application as a benign corrosion inhibitor for St37 steel in 15% H2 SO4 medium. ACS Appl Mater Interface 2017;9:6376–89, http://dx.doi.org/10.1021/acsami.6b14153. [24] Lu H, Zhang ST, Li WH, Cui YA, Yang T. Synthesis of graphene oxide-based sulfonated oligoanilines coatings for synergistically enhanced corrosion protection in 3.5% NaCl solution. ACS Appl Mater Interface 2017;9:4034–43, http://dx.doi.org/10.1021/acsami.6b13722. [25] Solomon MM, Gerengi H, Kaya T, Umoren SA. Performance evaluation of a chitosan/silver nanoparticles composite on St37 steel corrosion in a 15% HCl solution. ACS Sustain Chem Eng 2017;5:809–20, http://dx.doi.org/10.1021/acssuschemeng.6b02141. [26] Lalitha A, Ramesh S, Rajeswari S. Surface protection of copper in acid medium by azoles and surfactants. Electrochim Acta 2005;51:47–55, http://dx.doi.org/10.1016/j.electacta.2005.04.003. [27] Chen Y, Feng CY, Zhang Q, Ren GY, Han QX. N-halamine/pyridinium-derivatized magnetic sub-microparticles with synergetic biocidal properties. Appl Surf Sci 2019;467:526–33, http://dx.doi.org/10.1016/j.apsusc.2018.10.203. [28] Pareek S, Jain D, Hussain S, Biswas A, Shrivastava R, Parida SK, et al. A new insight into corrosion inhibition mechanism of copper in aerated 3.5 wt.% NaCl solution by eco-friendly imidazopyrimidine dye: experimental and theoretical approach. Chem Eng J 2019;358:725–42, http://dx.doi.org/10.1016/j.cej.2018.08.079. [29] Chen SJ, Xiang B, Chen SY, Zou XF, Zhou Y, Hou J. Synthesis and surface characterization of self-assembled monolayers of thiazoles incorporating hydrocarbon and fluorocarbon chains on copper substrates. Appl Surf Sci 2018;456:25–36, http://dx.doi.org/10.1016/j.apsusc.2018.06.082. [30] Huang HJ, Fu Y, Wang XC, Gao YC, Wang ZQ, Zhang ST, et al. Nano-to micro-self-aggregates of new bisimidazole-based copoly(ionic liquid)s for protecting copper in aqueous sulfuric acid solution. ACS Appl Mater Interface 2019;11:10135–45, http://dx.doi.org/10.1021/acsami.8b19993. [31] Xu WH, Han EH, Wang ZY. Nano-to micro-self-aggregates of new bisimidazole-based copoly(ionic liquid)s for protecting copper in aqueous sulfuric acid solution. J Mater Sci Technol 2019;35:64–75, http://dx.doi.org/10.1016/j.jmst.2018.09.001. [32] Khan MA, Alqadami AA, Otero M, Siddiqui MR, Alothman ZA, Alsohaimi I, et al. Heteroatom-doped magnetic hydrochar to remove post-transition and transition metals from water: synthesis, characterization, and adsorption studies. Chemosphere 2019;218:1089–99, http://dx.doi.org/10.1016/j.chemosphere.2018.11.210. [33] Wang YS, Zou Y, Tang YM. Inhibition effect and mechanism of sodium oleate on passivation and pitting corrosion of steel in simulated concrete pore solution. Construct Build Mater 2018;167:197–204, http://dx.doi.org/10.1016/j.conbuildmat.2018.01.17.

[34] Madhan Kumar A, Adesina AY, Hussein MA, Ramakrishna S, Al-Aqeeli N, Akhtar S, et al. PEDOT/FHA nanocomposite coatings on newly developed Ti-Nb-Zr implants: biocompatibility and surface protection against corrosion and bacterial infections. Mat Sci Eng C-Mater 2019;98:482–95, http://dx.doi.org/10.1016/j.msec.2019.01.012. [35] Park H, Lee SH, Kim FS, Choi HH, Cheong IW, Kim JH. Enhanced thermoelectric properties of PEDOT: PSS nanofilms by a chemical dedoping process. J Mater Chem A 2014;2:6532–9, http://dx.doi.org/10.1039/c3ta14960a. [36] Qiang YJ, Fu SL, Zhang ST, Chen SJ, Zou XF. Designing and fabricating of single and double alkyl-chain indazole derivatives self-assembled monolayer for corrosion inhibition of copper. Corros Sci 2018;140:111–21, http://dx.doi.org/10.1016/j.corsci.2018.06.012. [37] Zhang WF, Zhao QS, Liu T, Gao Y, Li Y, Zhang GL, et al. Phosphotungstic acid immobilized on amine-grafted graphene oxide as acid/base bifunctional catalyst for one-pot tandem reaction. Ind Eng Chem Res 2014;53:1437–41, http://dx.doi.org/10.1021/ie403393u. [38] Wang YB, Liu Z, Huang YD, Qi YT. The polymeric nanofilm of triazinedithiolsilane fabricated by self-assembled technique on copper surface. Part 2: Characterization of composition and morphology. Appl Surf Sci 2015;356:191–202, http://dx.doi.org/10.1016/j.apsusc.2015.08.099. [39] Zhang YZ, Zhou J, Zhang XL, Hu J, Gao H. Solvent polarity effect on quality of n-octadecanethiol self-assembled monolayers on copper and oxidized copper. Appl Surf Sci 2014;320:200–6, http://dx.doi.org/10.1016/j.apsusc.2014.09.070. [40] Wang P, Zhang D, Lu Z. Advantage of super-hydrophobic surface as a barrier against atmospheric corrosion induced by salt deliquescence. Corros Sci 2015;90:23–32, http://dx.doi.org/10.1016/j.corsci.2014.09.001. [41] Deng SD, Li XH, Du GB. Two ditetrazole derivatives as effective inhibitors for the corrosion of steel in CH3 COOH solution. J Mater Res Technol 2019;8:1389–99, http://dx.doi.org/10.1016/j.jmrt.2018.09.010. [42] Zhang J, Gong XL, Yu HH, Du M. The inhibition mechanism of imidazoline phosphate inhibitor for Q235 steel in hydrochloric acid medium. Corros Sci 2011;53:3324–30, http://dx.doi.org/10.1016/j.corsci.2011.06.008. [43] Gerengi H, Mielniczek M, Gece G, Solomon MM. Experimental and quantum chemical evaluation of 8-hydroxyquinoline as a corrosion inhibitor for copper in 0.1 M HCl. Ind Eng Chem Res 2016;55:9614–24, http://dx.doi.org/10.1021/acs.iecr.6b02414. [44] Zhang ZC, Ba HJ, Wu ZY, Zhu Y. The inhibition mechanism of maize gluten meal extract as green inhibitor for steel in concrete via experimental and theoretical elucidation. Construct Build Mater 2019;198:288–98, http://dx.doi.org/10.1016/j.conbuildmat.2018.11.216.

Please cite this article in press as: Feng Y, et al. The inhibition mechanism of a new synthesized indole derivative for copper in acidic environment via experimental and theoretical study. J Mater Res Technol. 2019. https://doi.org/10.1016/j.jmrt.2019.10.087