Experimental and Quantum Chemical Evaluation ... - ACS Publications

Subscriber access provided by Northern Illinois University

Article

Experimental and quantum chemical evaluation of 8hydroxyquinoline as a corrosion inhibitor for copper in 0.1 M HCl Husnu Gerengi, Micha# Mielniczek, Gokhan Gece, and Moses M Solomon Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b02414 • Publication Date (Web): 22 Aug 2016 Downloaded from http://pubs.acs.org on August 26, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Industrial & Engineering Chemistry Research is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1 Experimental and quantum chemical evaluation of 8-hydroxyquinoline as a corrosion inhibitor for copper in 0.1 M HCl Husnu Gerengia∗∗, Michal Mielniczekb, Gökhan Gecec, Moses M. Solomona a

Corrosion Research Laboratory, Kaynasli Vocational College, Duzce University, 81900

Kaynasli, Duzce, Turkey b

Department of Electrochemistry Corrosion and Materials Engineering, Gdansk University of

Technology, 11/12 Narutowicza Street, 80-233 Gdansk, Poland c

Department of Chemistry, Faculty of Natural Sciences, Architecture and Engineering, Bursa

Technical University, 16190 Bursa, Turkey

Abstract The corrosion inhibition properties of 8-hydroxyquinoline (8-HQ) in 0.1 M HCl for copper have been investigated by using experimental (electrochemical impedance spectroscopy (EIS), dynamic electrochemical impedance spectroscopy (DEIS), and potentiodynamic polarization) and theoretical methods complemented by surface morphological examination with the aid of scanning electron microscopy (SEM) and Electron Dispersive X-ray Spectroscopy (EDAX). Results obtained from all these applied techniques are in agreement and demonstrate that 8-HQ inhibited copper corrosion in 0.1 M HCl solution significantly and the inhibition efficiency varies directly with 8-HQ concentration. Potentiodynamic polarization results show that 8-HQ behaved like a cathodic type inhibitor in the studied system. EDAX results reveal that 8-HQ is most stable and effective at 10 h of immersion time. Inhibition of Cu corrosion by 8-HQ is due to electrostatic interaction between Cu surface and salt of 8-HQ according to ∆G 0ads value and FTIR results. EHOMO, ELUMO and ∆E values support the proposed physisorption mechanism. SEM and EDAX results confirm the adsorption of 8-HQ molecules on Cu surface.

Keywords: Copper; Corrosion; Corrosion inhibition; 8-hydroxyquinoline; HCl ∗

Corresponding author Tel.: +90-5053987953; E-mail: [email protected]

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 43

2 1. Introduction Copper and its alloys are fast becoming the preferred materials in nearly every aspect of industrial production; as integral component in building construction, power generation and transmission, electronic products, industrial machinery and transportation, and predominantly in sea water system 1. Boric 2 noted that copper global demand has outpaced all of its higher-profile precious peers by a significant margin over the last five years. The attractive features have been their excellent corrosion resistance, ease of fabrication during installation, low installation cost, and friendliness to the natural environment

1, 3

. However, copper tends to lose its corrosion

resistance ability when is deployed in long term service in a corrosive environment, particularly chloride ions containing environment. To safeguard and prolong the lifespan of this metal, the use of corrosion inhibitors is one of the many approaches 4, 5. Inorganic compounds such as chromates, nitrates, nitrites, etc. had been the common used corrosion inhibitors

6, 7

, however, the unhealthy influence of these compounds on human lives

and the natural environment have necessitated their discontinuation

8, 9

. Numerous organic

compounds have been investigated for inhibitive potential for copper in various corrosive environments. Ebadi et al.

10

studied the corrosion inhibition properties of pyrazolylindolenine

compounds, namely 4-(3,3-dimethyl-3H-indol-2-yl)-pyrazole-1-carbothioamide (InPzTAm), 4(3,3-dimethyl-3H-indol-2-yl)-1H-pyrazole-1-carbothiohydrazide (InPzTH) and 3,3-dimethyl-2(1-phenyl-1H-pyrazol-4-yl)-3H-indole (InPzPh),) on copper in 1 M HCl solution using electrochemical impedance spectroscopy, open circuit potential and linear scan voltammetry (LSV) techniques and found that InPzTAm, InPzTH, and InPzPh were capable of retarding copper corrosion in the studied environment by 94.0, 91.4, and 79.3% respectively. The investigation of Mihit et al.

11

on the corrosion inhibition of copper in 0.1 M HNO3 by 1,2,3,4-


Page 3 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3 tetrazole revealed that the organic compound adsorbed onto copper surface and prevented corrosion by 95%. Similarly, benzotriazole, 2-mercaptobenzoxazole, and 2-mercapto benzimidazole

12

, bis-(1-benzotriazolymethylene)-(2,5-thiadiazoly)-disulfide

13

, N-phenyl-1,4-

phenylene diamine 14, to mention but a few have been reported as effective organic inhibitors for copper in acid solutions. There are documentations in the literature on the effectiveness of 8-hydroxyquinoline (8HQ) (Fig. 1) as a corrosion inhibitor of several metals in different aggressive environments. For example, Liu et al.

15

reported the inhibition of the corrosion of aluminium alloy in 3.5% NaCl

solution by 8-hydroxyquinoline. Inhibition efficiency up to 96% was achieved by 5.52 mmol/L of the inhibitor. Geo et al. 16 reported 95% protection of AZ91D magnesium alloy in a mixture of Na2SO4, NaHCO3, and NaCl by 8-HQ. Also, inhibition efficiencies of 87.8 and 94.35% have been reported for copper and cold rolled steel in NaCl 17 and H2SO4 18 solution respectively by 8HQ. 8-HQ has also been reported as anticorrosive coatings for corrosion protection AA2024 20

19,

. To the best of our knowledge, there has been no report on the use of 8-HQ as inhibitor for

copper in HCl environment. The aim of the present paper is to extend the study on the inhibitive properties of 8-HQ (Fig. 1) for copper to HCl medium using Potentiodynamic Polarization (PDP), Electrochemical Impedance Spectroscopy, and Dynamic Electrochemical Impedance Spectroscopy methods. The experimental results are complemented with surface morphological studies (SEM and FTIR) and theoretical calculations in order to provide an explanation to the adsorption mechanism of 8-HQ onto copper surface in HCl solution.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 43

4 2. Experimental Approach 2.1 Materials The working electrodes were first prepared using 500-2000 grade abrasive paper; following this procedure, they were rinsed with distilled water and degreased with acetone. Silver/Silver chloride (Ag/AgCl) and Pt-mesh were used as reference and auxiliary electrodes, respectively. All measurements were performed at room temperature. The exposed surface area of the working electrodes in the solution was 1.13 cm2 and all EIS measurements were performed starting after immersion for 120 min in 0.1 M HCl solution. This time was selected with measuring open circuit potential and 120 min is enough to obtain stable state for investigated system. Tafel polarization method applied immediately after EIS measurements with same cell used in EIS. The chemical composition of the working electrode was minimum 99.9% copper. The DEIS measurements were performed only for without and with maximum concentration of inhibitor. Each experiment was repeated at least seven times to ensure that the most accurate agreement was achieved. All chemicals were obtained from Merck, with purity listed as follows: HCl (37%) and 8-HQ (99.9%). The concentration range of 8-HQ used were 0.004 M, 0.008 M, 0.012 M and 0.016 M. 2.2. Electrochemical measurements Electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements were carried out using a GAMRY PC3/600 potentiostat/galvanostat/ZRA system. Tafel polarization curves were recorded by changing the electrode potential automatically from -250 to +250 mV versus Ag/AgCl (3 M KCl) with scanning rate of 0.166 mV/s. Tafel polarization curves were analysed by using software Gamry Echem Analyst programme. EIS measurements were performed within frequency range from 100 kHz to 0.03 Hz and with amplitude of 10 mV.


Page 5 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


5 DEIS measurements were carried out using fast home-build galvanostat. The generation of the multi ‐ sinusoidal perturbation was performed with a National Instruments Ltd. PCI-4461 digitalanalog card 21. The same card was used to measure the current and voltage signals. The sampling frequency was 12.8 kHz 21. The perturbation signal was a package composed of current sinusoids with the frequency range from 4.5 kHz to 0.03 Hz. Obtained impedance data from EIS and DEIS were calculated by using ZsimpWin 3.21 software. 2.3. Surface morphological studies The surface analysis of studied copper sample was investigated by means of SEM (FEI, Model: Quanta FEG 250) and EDAX probe (accelerator voltage 20 keV) after DEIS measurements. SEM and EDAX analysis were made before immersion in the corrosive medium, without and with maximum concentration (0.016 M) of 8-HQ. 2.4. Quantum chemical calculations All calculations have been performed using standard gradient techniques and default convergence criteria with the Gaussian 09 package

22

. The calculated geometries showed no

imaginary frequencies and consequently proved to be minima on the potential hyper surface. Molecular properties such as ionisation potential, electronegativity, chemical potential, and chemical hardness have been deduced from HOMO–LUMO analysis in the gas and aqueous phases employing B3LYP functional and a triple-zeta basis set augmented with polarization and diffuse functions, 6-311++G(d,p) basis set as well as within the integral equation formalism polarizable continuum model (IEF-PCM) with water as solvent.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 43

6 3. Results and Discussion 3.1. Potentiodynamic measurements Figure 2 illustrates the polarization curves for copper in 0.1 M HCl in the absence and presence of various concentrations of 8-HQ. The corresponding parameters namely, corrosion current density (Icorr), corrosion potential (Ecorr), anodic and cathodic Tafel slopes (βa and βc) deduced by extrapolating the linear portions of the anodic and cathodic curves

12, 13, 17

are given

in Table 1. The polarisation resistance (Rp) which was calculated using the Stern–Geary Equation 23

(Eq. 1)

and the percentage inhibition efficiency (IE%) gotten from Eq. 2 are also listed in

Table 1. I corr =

βa βc 1 2.303(β a + β c ) R p

IE (%) =

I corr − I corr(inh) I corr

(1)

× 100

(2)

where βa, βc, Icorr , and Icorr(inh) are the anodic slope, cathodic slope, corrosion current density measured in acid solution without inhibitor and corrosion current density determined in solutions containing inhibitor respectively. Generally, it is believed that the cathodic reaction of copper in an aerated acidic chloride solution free of inhibitor is the reduction of oxygen in the solution 14, 24: 4H+ + O2+ 4e-

2H2O

(3)

In HCl solution having concentration less than 1 M, the acceptable anodic oxidative dissolution reactions of Cu are 24, 25: Cu

Cu+ + e- (fast)

(4)

Cu+

Cu2+ + e- (slow)

(5)


Page 7 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


7 However, authors 14, 27 have noted that Cu+ reaction with Cl- is faster compared to the reaction of Cu2+ with Cl-. As effect, CuCl is the predominant copper chloride compound in chloride containing solutions. Cu+ + Cl-

CuCl

(6)

It is known that CuCl has poor adhesion power, as such, it would be unstable and transform to − 14

:

CuCl2

−

CuCl + Cl-

(7)

CuCl2

The anodic dissolution of copper is therefore controlled by both electro-dissolution and diffusion of CuCl−2 to the bulk solution

14, 28

. Nevertheless, the metal surface can be protected by the

precipitation of the insoluble CuCl or the adsorption of the soluble CuCl−2 complex onto the surface. Tansug et al.

28

and Sherif and Park

14

, however, reported that the insoluble CuCl

protective layer is destroyed in aggressive acid environment and the adsorbed CuCl−2 complex dissolves according to Eq. 8: −

CuCl2 ads

Cu2+ + 2Cl- + e-

(8)

The total corrosion reaction of copper in acidic chloride solution is given as 13: 2Cu + 4H+ + 4Cl- + O2

2Cu2+ + 4Cl- + 2H2O

(9)

Inspection of Figure 2 reveals that the anodic branch of the Tafel curve for Cu in the uninhibited acid solution exhibits three distinctive regions: (i) a region of monotonic increase in current with potential until the current attain a maximum which is indicative of the oxidation of Cu according to Eq. 4 14; (ii) a region of decreasing current density with rise in potential until a minimum value is attained. This region signifies the interaction of Cu+ with Cl- leading to the formation of CuCl (Eq. 6) and (iii) the region of sharp increase in current density with potential



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 43

8 which indicates the transformation of CuCl into CuCl−2 complex according to Eq. 7. By comparing the anodic branch of the Tafel curves for the inhibited systems to that of the uninhibited, it could be seen that they are similar suggesting that the overall Cu corrosion mechanism was not changed on addition of 8-HQ. However, it can be seen that the decreasing of current density with increase in potential in the second region is more pronounced in the inhibited systems than the uninhibited while the sudden rise in current density as noticed in the third region of the anodic curve of the free acid solution almost disappear in the inhibited curves. This may be interpreted to mean interference of adsorbed inhibitor molecules on the Cu corrosion reactions and the slowing down of the reaction rate. Also worthy of note in Figure 2 is the significant displacement of the corrosion potential (Ecorr) towards more negative direction by 8-HQ. This behavior is a characteristic of a cathodic-type inhibitor. From Table 1, it is observed that the βa values of the inhibited acid solutions are bigger compared to that of the blank solution and followed no pattern with increasing inhibitor concentration whereas the reverse is noticed for the βc. This suggests the predominant effect of 8-HQ on cathodic reactions than anodic. The observed steady decrease in βc values with increasing inhibitor concentration may mean alteration of the mechanism of cathodic processes by 8-HQ which could arise from the thickening of the electrical double layer due to the adsorption of 8-HQ molecules onto Cu surface 10. It is also obvious in the table that the corrosion current density (Icorr) values of the acid solutions containing 8-HQ are significantly smaller while polarization resistance (Rp) values are bigger compared to those of the free acid solution. This indicate inhibition of Cu corrosion in 0.1 M HCl solution by 8-HQ. However, the inhibition ability is found to be a function of inhibitor concentration. For instance, the Icorr and Rp values of the lowest studied concentration of 8-HQ (4 mM) are 36 µA/cm2 and 625 Ωcm2 respectively


Page 9 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


9 corresponding to inhibition efficiency of 43%. When the concentration was increased from 4 mM to 16 mM, the Icorr and Rp values also changed to 15 µA/cm2 and 1420 Ωcm2 respectively and the inhibition efficiency increased to 76%. In corrosion literature

29, 30

, an inhibitor is regarded as anodic type if the difference

between Ecorr of the uninhibited and inhibited systems is –85 mV or more negative, cathodic type if the value is +85 mV or greater, otherwise the inhibitor is considered as mixed type. To characterize 8-HQ as cathodic, anodic, or mixed type inhibitor in the studied system, the difference between the Ecorr value of the blank acid solution and those for acid solution containing 8-HQ was computed. The values obtained are 56, 69, 90, and 104 mV for 4 mM, 8 mM, 12 mM, and 16 mM 8-HQ respectively. Judging from these values and with reference to the bench mark value of ± 85 mV, it could be concluded that the lower concentrations (4 mM and 8 mM) behaved as mixed type corrosion inhibitor but with principal effect on the cathodic reactions while the higher concentrations (12 mM and 16 mM) acted majorly as cathodic type inhibitor in the studied system. 3.2. EIS measurements Electrochemical impedance spectroscopy is a powerful tool which had been used to gain insight into metal corrosion and adsorption phenomena 28, 31, 32. EIS experiments were conducted to have a clearer picture of the corrosion and corrosion inhibition of Cu in 0.1 M HCl in the absence and presence of 8-HQ. Figure 3 shows the EIS plots obtained for this system in (a) Nyguist, (b) Bode modulus, and (c) Phase angle representations. The Nyguist plots are characterized by distorted semicircles and are always attributed to heterogeneity of working electrode surface 27, 33. The effect of addition of 8-HQ into the acid solution is eminent; the size of the semicircle in the Nyguist plot (Fig. 3(a)), the impedance of the Bode modulus (Fig. 3(b)),



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 43

10 and the Phase angle (Fig. 3(c)) increased. The increase is dependent on the concentration of 8HQ and the highest effect is observed with 16 mM 8-HQ. This observation could be interpreted to mean protection of Cu surface in the corrosive environment which could be possible due to the adsorption of the inhibitor molecules onto the surface. By closely examining Figure 3(b and c), three outstanding regions can be spotted. First, the region of higher frequency whereby the values of log/Z/ in Figure 3(b) are low and tend to be near constant while the corresponding Phase angle values in Figure 3(c) fall steadily towards zero. According to Zhang et al.

13

, this is indicative of resistive behaviour and corresponds to

solution resistance. The second distinctive region is the linear relationship existing between log/Z/ versus log f in the intermediate frequency (Fig. 3(b)); at this point, the Phase angle almost reached its climax (Fig. 3(c)) and finally, at the lower frequency, log/Z/ appears to be independent of log f. This behaviour is typical of Warburg impedance and signifies a diffusion controlled corrosion process involving the transport of reactants from the bulk solution to the metal/solution interface or transport of soluble products from the metal/solution interface to the bulk solution 13. The Nyquist plots were analyzed using the equivalent circuit shown in Figure 4. This circuit had been previously used by Zhang et al.

24

to analyze impedance data for the corrosion

and corrosion inhibition of copper in 0.5 M HCl without and with some amino acids. The equivalent circuit consists of Warburg impedance, resistor, and Constant Phase Elements represented in the figure as W, R, and Q respectively. Rs and Rct denote solution resistance and charge transfer resistance respectively. The Phase angle element was used to compensate for the observed Cu surface roughness and is defined as 12, 24: Q = Y 0 ( jw)

n

(10)


Page 11 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


11 where j = imaginary root, w = angular frequency, Y 0 = magnitude and n = the Phase shift. If

n has values n =1, 0, -1, Q becomes capacitor, resistance and inductance respectively. In range of values of n between 0 and 1, Q describes non-ideal behaviour of capacitor. More so, value of

n =0.5 signifies Warburg impedance

15

. The derived impedance parameters for the studied

system are given in Table 2. The percentage inhibition efficiency also listed in the table was computed using the Rct values in the absence and presence of 8-HQ according to the following equation 34: IE =

R ct − R ct 0 R ct 0

(11)

where R0ct and R ct are the charge transfer resistance values with and without 8-HQ respectively. As could be seen from the table, the value of n for all the considered systems can be approximated to 0.5, implying Warburg impedance and confirms the presence of diffusion at low frequencies. This is in perfect agreement with the PDP results. Further inspection of Table 2 reveals that CPE values are smaller compared to those of the free acid solution and further decrease with increasing concentration of 8-HQ. The decrease in CPE is in accordance with the famous Helmholtz model given as C = ε o ε / d

35

, where ε o is the permittivity of vacuum, ε is

the relative permittivity of the inhibitor film, and d is the film thickness and hence provide experimental evidence of adsorption of 8-HQ molecules onto Cu surface in 0.1 M HCl solution. Also from Table 2, it is observed that Rct varies directly with percentage inhibition efficiency. For instance, the Rct value of 0.1 M HCl solution containing 4 mM 8-HQ is 405.4 Ωcm2 and corresponds to IE of 47%. When the concentration of the inhibitor was increased to 16 mM, the Rct value increased to 1015 Ωcm2 and as a consequent the IE was stepped up to 79%. This seems

to suggest that as the concentration of the inhibitor was increased, the thickness of the adsorbed



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 43

12 inhibitor layer increased also and posed serious obstruction to the movement of corrosive agents from the bulk solution to the metal surface.

3.3. DEIS measurements Dynamic Electrochemical Impedance Spectroscopy (DEIS) was employed in this study to track the changes occurring in the adsorbed 8-HQ layer on Cu surface in 0.1 M HCl solution after long immersion time. Figure 5 shows the DEIS spectra obtained for Cu exposed to 0.1 M HCl in the absence and presence of 16 mM 8-HQ for 15 h. Similar spectra were obtained at 5 and 10 h (not shown). The DEIS data were analyzed using the equivalent circuit in Figure 3 which was used for EIS data analysis and the derived parameters are listed in Table 3.

The

spectra in Figure 5 look like a flattened semicircle at the high frequency region and have tail which terminates at the low frequency region. The uninhibited and inhibited solutions spectra are very similar implying same mechanism in the two systems. However, in contrast, the spectrum obtained for the 8-HQ inhibited acid solution is bigger and seems to have a peak at 10 h. The larger size may mean corrosion inhibition and the peak at 10 h may indicate maximum protection. By examining the results presented in Table 3 and the graph of Rct against immersion time given in Figure 6, it is observed that Rct varies in like manner as those obtained from EIS measurements; i.e Rct of inhibited solution is greater than that of uninhibited solution. However, Rct is found to increase with increasing immersion time reaching an optimum value of 1070.0

Ωcm2 at 15 h of exposure time. With this increase in Rct value with immersion time, one should expect a corresponding increase in percentage inhibition efficiency as authors

36, 37

have

attributed such increase to the formation of an insulating protective film at the metal/solution interface. Surprisingly, this is not the case; as Rct increased from 959 Ωcm2 at 10 h to 1070.00


Page 13 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


13 Ωcm2 at 15 h, IE decreased from 66% to 62% (Table 3). The n value seems to give a clearer picture to the changes occurring at the Cu surface with immersion time. As could be seen in Table 3, the value of n in 5 and 10 hrs are bigger than those of the free acid solution suggesting increase in heterogeneity of the metal surface which could arise from adsorption of the inhibitor molecules. It also described a non-stationary system at this immersion time

38

. The increase in

the Cu surface roughness in the first 9 h can be clearly seen in Figure 7; for instance, n value increases rapidly towards nobler direction. However, at 10 h, it should be noted that n values of both blank and inhibited solutions are near constant suggesting that the corrosion system approached a stationary state. It became prominent at 15 h and the n values of both the free acid and inhibited acid solutions became same. At this point, the graphs of both systems are almost parallel (Fig. 7). It appears like, as the 0.1 M HCl solution containing 16 mM 8-HQ eventually became stationary at longer exposure time, the adsorption-desorption equilibrium shifted towards desorption resulting in the observed decrease in IE.

3.4. The adsorption isotherm study The surface coverage (θ) is an essential factor which can be used in the description of the nature of interaction between metal surface and inhibitor molecules. Commonly used adsorption isotherms are Langmuir, El-awady et al. kinetic/thermodynamic, Frumkin, Temkin, and Frundlich adsorption isotherms. They all have the general form 39:

f (θ , x ) exp(− 2aθ ) = K ads C

(12)

where f (θ , x ) is the configurational factor and depends on the physical model and assumptions underlying the derivation of the equation, a is molecule interaction parameter, K ads represents the equilibrium constant of adsorption-desorption process, and C stands for the concentration of inhibitor. The surface coverage is related to percentage inhibition efficiency as: θ = IE 100 . The



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 43

14 best fit to an adsorption model is usually adjudged from the value of linear regression coefficient (R2); for an ideal system, R2 = 1. To assess the adsorption mechanism of 8-HQ molecules onto Cu surface in 0.1 M HCl solution, θ values computed from IE% given in Tables 1 and 2 were fitted into various adsorption isotherms. Judging from the R2 values given in Table 4 and the linearity of the graphs in Fig. 8, it could be said that the adsorption process obeyed Langmuir adsorption isotherm which has the following specific equation 37: C

θ

=

1

+C

(13)

K ads

However, it is observed that the slope (Table 4) remarkably deviated from unity required by an ideal Lagmuir isotherm model. Interaction among adsorbed 8-HQ molecules on the metal surface might be responsible for the observed deviation. Langmuir equation had been derived under the assumption that adsorbed species do not interact with each other 40. This assumption is not true as authors

33, 41, 42

have demonstrated that adsorbed inhibitor species are capable of interacting

with each other on metal surface. For this reason, the values of θ were fitted into El-Awady kinetic/thermodynamic adsorption model which is a modification of the Langmuir isotherm and takes into consideration the omitted interaction parameter by Langmuir isotherm. Equation 14 31 gives the description of the El-Awady kinetic/thermodynamic adsorption model. Log

θ 1−θ

= log K ads + y log C inh

K ads is equal to

.

(14)

represents the number of active sites occupied by an inhibitor

molecule or the number of water molecules replaced by an inhibitor molecule

33

. The straight

 θ  line graphs obtained by plotting ln  against log C are shown in Fig. 9. All the adsorption 1−θ 

parameters derived from Fig. 8 and 9 are listed in Table 4. As could be seen from the table, the values of 1/y are more than unity implying that each of the inhibitor specie occupied more than one active site on the Cu surface. It is interesting to note from the table that K ads values gotten from El-Awady et al. isotherm are bigger than those obtained from the Langmuir plot. This clearly shows that the El-Awady et al. kinetic/thermodynamic isotherm describe the adsorption process of 8-HQ onto copper surface better than Langmuir isotherm. K ads value denotes the


Page 15 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


15 strength of the bond between adsorbate and adsorbent 39, 43. From the values of K ads , the standard Gibbs free energy of adsorption ( ∆G 0ads ) for the studied system was calculated using the equation 44

:

0   1 − ∆ G ads   exp K ads =  RT  55.5  

(14)

where 55.5 is the concentration of H2O expressed in mol/dm3, R is the molar gas constant, and T is absolute temperature. In corrosion literature 40-42, ∆G 0ads value up to -20 kJ/mol is indicative of physical adsorption mechanism whereas that more negative than -40 kJ/mol is taken to signifies chemisorption mechanism. The calculated value for ∆G 0ads in this system ranged between -5.76 kJ/mol and -8.90 kJ/mol; hence we submit that physisorption mechanism was the predominant mechanism in the adsorption of 8-HQ molecules onto Cu surface. To further explain the physical adsorption mechanism involved in the adsorption of 8-HQ onto Cu surface in 0.1 M HCl solution as indicated by ∆G 0ads values, FTIR experiments were performed for 8-HQ before and after adding to 0.1 M HCl solution. The spectra obtained from the experiments are displayed in Figure 10. Clearly, the N-H stretching peak can be seen at about 3300 cm-1 in the spectrum obtained for acid solution containing 8-HQ. This peak is absent in the spectrum obtained for 8-HQ before adding to the acid solution and therefore provide an experimental evidence for the formation of electrostatic bond between N-atom of 8-HQ and the proton from HCl acid. This reaction is possible because N atom in 8-HQ is more basic than O heteroatom also present in the molecule; meaning that in the acid solution, 8-HQ is present as a soluble salt as exemplify in the following reaction:



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 43

16

(15)

The 8-HQ salt is attracted onto Cu surface in the studied environment through the so-called columbic electrostatic attraction and not by electron sharing mechanism.

3.5. Quantum chemical studies To guide the search for inhibitor compounds with tailored properties, experimental corrosion studies are often accompanied by electronic structure calculations based on density functional theory

45-48

. Evidence from earlier analytical measurements propound that chemical

properties of 8-HQ are strictly dependent upon pH change, and at pH values lower than pH=3, 8HQ is exclusively in the protonated quinolinium form, whereas it is in the deprotonated quinolinate form at pH values larger than 12. In neutral water, the predominant form is the neutral enolic form

49

. Considering the highly acidic pH used in the experimental parts of this

study, this is the gist of why our theoretical calculations particularly focus on neutral and also protonated forms of 8-HQ. To validate the optimized geometry of the compound, some selected geometric parameters are listed in Table 5, with reference atom numbering given in Figure 1, and have been compared to those obtained by X–ray diffraction analysis for the crystal structure of 8HQ

50

. Bond lengths and angles found for the neutral form of 8-HQ do not deviate much from

the experimental values, and accordingly, would allow for a transition to the energy calculations of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The frontier molecular orbital distributions of neutral and protonated forms of 8-HQ are shown in Figure 11. The HOMO of neutral form of 8-HQ (Fig. 11a) show delocalized electron density contributed from hydroxyl group oxygen atom of carbocyclic ring and from


Page 17 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


17 nitrogen atom of pyridine ring. The LUMO finds predominant contribution from backbone carbon-hydrogen σ-bonds. A similar delocalized electron density at HOMO and LUMO of protonated form of 8-HQ exists (Fig. 11b). According to Koopmans’ theorem 51, the negative of the HOMO energy (-EHOMO) and the LUMO energy (-ELUMO) correspond to ionization potential and electron affinity, respectively (i.e. I = -EHOMO and A = -ELUMO). The chemical hardness (η), electronegativity (χ), and chemical potential (µ) are thereby defined as µ = 1/2 (EHOMO +ELUMO), η = (ELUMO-EHOMO)/2 and χ = - (ELUMO+EHOMO)/2. As could been seen in Table 6, the EHOMO and ELUMO values for the neutral form of 8-HQ molecule in both gas and aqueous phases,

respectively are more positive compared to those of the protonated form. The values of ∆E for the neutral form of 8-HQ molecule in both phases are also seen to be bigger than those of the protonated form. All these suggest that the dominant form responsible for the inhibition efficiency of 8-HQ is its protonated form in acidic medium. It is interesting to note that the neutral form of 8-HQ has lower dipole moment values when compared with those for its protonated form, which probably favors the physical adsorption between protonated inhibitor species and copper surface 52. The fraction of electrons transferred (∆N) is given by: ∆N = (χCu – χ8-HQ) / 2(ηCu - η8-HQ) and the corresponding values are also presented in Table 6 for the neutral

and protonated forms in both the gas and aqueous phases. To calculate this fraction, a theoretical value for the electronegativity of bulk copper, χCu = 4.48 eV/mol 53, and a global hardness of ηCu = 0 eV/mol were used based on the assumption that for a bulk metal I = A because they are softer than the neutral metallic atoms 54. If ∆N < 3.6, the inhibition efficiency enhances with increasing electron-donating ability to the metal surface as in Lukovits’s work

55

. Since 8-HQ is more

electronegative than the densely packed copper surface, the charge would flow to 8-HQ from copper surface (∆N < 0), which has been verified by the explicitly calculated charge transfer.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 43

18

3.6. Morphological measurements SEM and EDAX measurements were carried out to show that the corrosion inhibition of Cu in 0.1 M HCl solution containing 8-HQ was due to the formation of adsorptive film on the surface. Figures 12 and 13 show the SEM images and EDAX spectra respectively obtained for copper (a) in abraded state (b) exposed to 0.1 M HCl solution, (c) exposed to 0.1 M HCl solution containing 0.016 M 8 HQ for 2 h. It can be seen that the image in Fig. 12(a) is smooth and the spectrum in Fig. 13(a) record 100% elemental composition of Cu. The surface is rather greatly damaged on exposure to the acid solution (Fig. 12(b)) as evident by the remarkable decrease in the percentage composition of Cu to 72.15% (Fig. 13(b)). However, by comparing Fig. 12(c) and Fig. 13(c) with Fig. 12(b) and Fig. 13(b), it is obvious that the surface in Fig. 12(b) is repaired in Fig. 12(c); the surface is smoother while new peaks (C and N peaks) can be seen in Fig. 13(c) thereby confirming the adsorption of 8-HQ on Cu surface in 0.1 M HCl environment.

4. Conclusions The corrosion and corrosion inhibition process of Cu in HCl environment without and with 8-HQ have been studied using both theoretical and experimental approaches. 8-HQ is found to be effective in retarding the dissolution of Cu in the studied acid solution but the extent of inhibition is a function of inhibitor concentration and immersion time. Inhibition is brought about by formation of protective adsorption film on the metal surface. The adsorption of 8-HQ is via physical adsorption mechanism whereby soluble salt of the inhibitor is attracted towards charged Cu surface. 8-HQ demonstrates predominant influence on the cathodic reactions than anodic reactions. SEM and EDAX results confirm the adsorption of 8-HQ molecules onto Cu surface. There is a fair agreement between the calculated electronic and global reactivity parameters of


Page 19 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


19 the protonated form of 8-HQ and the experimental findings, which reveals that the protonated molecule is most likely to interact with the copper surface through physisorption.

5.

Acknowledgements

The authors gratefully acknowledge the financial support of this work by the Duzce University Research Fund (Project No: BAP-2015.26.04.365).

References (1)

Hammouti, B.; Dafali, A.; Touzani, R.; Bouachrine, M. Inhibition of Copper Corrosion by Bipyrazole Compound in Aerated 3% NaCl. J. Saudi Chem. Soc. 2012, 16, 413 – 418.

(2)

Boric, J. Investing in Copper - A Bullish Scenario for Copper, a Daily Reckoning Whitepaper Report (www.dailyreckoning.com/investing-in-copper/; Accessed 13th June, 2016)

(3)

Finšgar, M.; Milošev, I. Inhibition of Copper Corrosion by 1,2,3-Benzotriazole: A review. Corros. Sci. 2010, 52 (9) 2737–2749

(4)

Sherif, E. M.; Park, S. M. 2-Amino-5-ethyl-1,3,4-thiadiazole as a Corrosion Inhibitor for Copper in 3.0% NaCl Solutions. Corros. Sci. 2006, 48, 4065–4079

(5)

Sherif, E. S. M.; Erasmus, R. M.; Comins, J. D. Effects of 3-amino-1, 2, 4-triazole on the inhibition of copper corrosion in acidic chloride solutions. J. Colloid Interf. Sci. 2007, 311(1), 144-151

(6)

Saji, V. S.; Shibli, S. M. A. Synergistic Inhibition of Carbon Steel Corrosion by Sodium Tungstate and Sodium Silicate in Neutral Aqueous Media. Anti-Corros. Meth. Mater. 2002, 49, 433 – 443. Shibli, S. M. A.; Saji, V. S. Co-inhibition Characteristics of Sodium Tungstate with Potassium Iodate on Mild Steel Corrosion. Corros. Sci. 2005, 47, 2213 – 2224. Toxicological Profile for Chromium, Agency for Toxic Substance. US Public Health Service, Report no. ATSDR/TP-88/10, 1989. U. S. Congress, Office of Technology Assessment, Environmental Policy Tools: A User’s Guide, OTA-ENV-634. Washington, DC: U.S. Government Printing Office, 1995. Ebadi, M.; Basirun, W. J.; Khaledi, H.; Ali, H. M. Corrosion Inhibition Properties of Pyrazolylindolenine Compounds on Copper Surface in Acidic Media. Chem. Central J. 2012, 6, 163 – 173.

(7) (8) (9) (10)

(11)

Mihit, M.; Laarej, K.; Abou El Makarim, H.; Bazzi, L.; Salghi, R.; Hammouti, B. Study of the Inhibition of the Corrosion of Copper and Zinc in HNO3 Solution by



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 43

20 Electrochemical Technique an Quantum Chemical Calculations. Arabian J. Chem. 2010, 3, 55 – 60. (12)

(13)

Zhang, D.; Gao, L.; Zhou, G. Inhibition of Copper Corrosion in Aerated Hydrochloric Acid Solution by Heterocyclic Compounds Containing a Mercapto Group. Corros. Sci. 2004, 46, 3031 – 3040. Zhang, D.; Gao, L.; Zhou, G. Inhibition of Copper Corrosion by Bis-(1benzotriazolymethylene)-(2,5-thiadiazoly)-disulfide in Chloride Media. Appl. Surf. Sci. 2004, 225, 287 – 293.

(14)

Sherif, E.M.; Park, S. M. Inhibition of Copper Corrosion in Acidic Pickling Solutions by N-phenyl-1,4-phenylenediamine. Electrochim. Acta 2006, 51, 4665 – 4673.

(15)

Liu, W.; Singh, A.; Lin, Y.; Ebenso, E. E.; Zhou, L.; Huang, B. 8-Hydroxyquinoline as an Effective Corrosion Inhibitor for 7075 Aluminium Alloy in 3.5% NaCl Solution. Int. J. Electrochem. Sci. 2014, 9, 5574 – 5584.

(16)

Gao, H.; Li, Q.; Dai, Y.; Luo, F.; Zhang, H. X. High Efficiency Corrosion Inhibitor 8Hydroxyquinoline and its Synergistic Effect with Sodium Dodecylbenzenesulphonate on AZ91D Magnesium Alloy. Corros. Sci. 2010, 52, 1603 – 1609.

(17)

Cicileo, G. P.; Rosales, B. M.; Varela, F. E.; Vilche, J. R. Inhibitory Action of 8Hydroxyquinoline on the Copper Corrosion Process. Corros. Sci. 1998, 40, 1915 – 1926.

(18)

Tang, L.; Li, X.; Si, Y.; Mu, G.; Liu, G. The Synergistic Inhibition between 8Hydroxyquinoline and Chloride Ion for the Corrosion of Cold Rolled Steel in 0.5 M Sulfuric Acid. Mater. Chem. Phys. 2006, 95, 29 – 38.

(19)

Snihirova, D.; Lamaka, S. V.; Cardoso, M. M.; Condeço, J. A. D.; Ferreira, H. E. C.; Montemor, M.F. pH-Sensitive Polymeric Particles with Increased Inhibitor-Loading Capacity as Smart Additives for Corrosion Protective Coatings for AA2024. Electrochim. Acta 2014, 145, 123–131

(20)

Snihirova, D.; Liphardt, L.; Grundmeier, G.; Montemor, F. Electrochemical Study of the Corrosion Inhibition Ability of “smart” Coatings Applied on AA2024. J Solid State Electrochem. 2013, 17,2183–2192

(21)

Gerengi, H.; Bereket, G.; Kurtay, M. A Morphological and Electrochemical Comparison of the Corrosion Process of Aluminum Alloys under Simulated Acid Rain Conditions. J. Taiwan Inst. Chem. Eng. 2016, 58, 509 – 516.

(22)

Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, Jr., J. A.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.;


Page 21 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


21 Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, Revision C.01; Gaussian, Inc.: Wallingford CT, 2009. (23)

Gerengi, H.; Sahin, H. I. Schinopsis lorentzii Extract as a Green Corrosion Inhibitor for Low Carbon Steel in 1 M HCl Solution. Ind. Eng. Chem. Res. 2012; 51, 780 – 787.

(24)

Zhang, D.; Cai, Q.; He, X.; Gao, L.; Zhou, G. Inhibition Effect of Some Amino Acids on Copper Corrosion in HCl Solution. Mater. Chem. Phys. 2008, 112 353 – 358. Khaled, K. F.; Hackerman, N. Ortho-substituted Anilines to Inhibit Copper Corrosion in Aerated 0.5 M Hydrochloric Acid. Electrochim. Acta 2004, 49, 485 – 495.

(25)

(26)

Ismail, K. M. Evaluation of Cysteine as Environmentally Friendly Corrosion Inhibitor for Copper in Neutral and Acidic Chloride Solutions. Electrochim. Acta 2007, 52, 7811 – 7819.

(27)

Larabi, L.; Benali, O.; Mekelleche, S. M.; Harek, Y. 2-Mercapto-1-methylimidazole as Corrosion Inhibitor for Copper in Hydrochloric Acid. Appl. Surf. Sci. 2006, 253, 1371 – 1378.

(28)

Tansuğ, G.; Tüken, T.; Kıcır, N.; Erbil, M. Investigation of 2-aminoethanethiol as Corrosion Inhibitor for Steel using Response Surface Methodology (RSM). Ionics 2014, 20, 287 – 294.

(29)

Solomon, M. M.; Umoren, S. A. In-situ Preparation, Characterization and Anticorrosion Property of Polypropylene Glycol/silver Nanoparticles Composite for Mild Steel Corrosion in Acid Solution. J. Colloid Interf. Sci. 2016, 462, 29 – 41.

(30)

Solomon, M. M.; Umoren, S. A.; Abai, E. J. Poly(methacrylic acid)/silver Nanoparticles Composites: In-situ Preparation, Characterization and Anticorrosion Property for Mild Steel in H2SO4 Solution. J. Mol. Liq. 2015; 212, 340 – 351.

(31)

Solomon, M. M.; Umoren, S. A.; Israel, A. U.; Etim, I. G. Synergistic Inhibition of Aluminium Corrosion in H2SO4 Solution by Polypropylene Glycol in the Presence of Iodide Ions. Pigm. Res. Technol. 2016, 45(4), 280 - 293.

(32)

Gerengi, H.; Ugras, H. I.; Solomon, M. M.; Umoren, S. A.; Kurtay, M.; Atar, N. Synergistic Corrosion Inhibition Effect of 1-ethyl-1-methylpyrrolidinium tetrafluoroborate and Iodide Ions for Low Carbon Steel in HCl Solution. J. Adhes. Sci. Technol. 2016; 30, 2383 – 2403.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 43

22 (33)

Solomon, M. M.; Umoren, S. A. Electrochemical and Gravimetric Measurements of Inhibition of Aluminium Corrosion by Poly (methacrylic acid) in H2SO4 Solution and Synergistic Effect of Iodide Ions. Measurement 2015, 76, 104 – 116.

(34)

Vrsalović, L.; Gudić, S.; Kliškić, M.; Oguzie, E. E.; Carev, L. Inhibition of Copper Corrosion in NaCl Solution by Caffeic Acid. Int. J. Electrochem. Sci. 2016, 11, 459 – 474.

(35)

Singh, A. K.; Quraishi, M. A. Investigation of the Effect of Disulfiram on Corrosion of Mild Steel in Hydrochloric Acid Solution. Corros. Sci. 2011, 53, 1288 – 1297.

(36)

Jayaperumal, D. Effects of Alcohol-based Inhibitors on Corrosion of Mild Steel in Hydrochloric Acid. Mater. Chem. Phys. 2010; 119, 478 – 484. Yadav, M.; Kumar, S.; Gope, L. Experimental and Theoretical Study on Amino Acid Derivatives as Eco-friendly Corrosion Inhibitor on Mild Steel in Hydrochloric Acid Solution. J. Adhes. Sci. Technol.2014, 28, 1072 – 1089.

(37)

(38)

Gerengi, H.; Darowicki, K.; Bereket, G.; Slepski, P. Evaluation of Corrosion Inhibition of Brass-118 in Artificial Seawater by Benzotriazole using Dynamic EIS. Corros. Sci. 2009, 51, 2573 – 2579.

(39)

Solomon, M. M.; Umoren, S. A. Enhanced Corrosion Inhibition Effect of Polypropylene Glycol in the Presence of Iodide Ions at Mild Steel/Sulphuric Acid Interface. J. Environ. Chem. Eng. 2015, 3, 1812 – 1826.

(40)

Solomon, M.M.; Umoren, S.A.; Udosoro, I.I.; Udoh, A.P. Inhibitive and Adsorption Behaviour of Carboxymethyl Cellulose on Mild Steel Corrosion in Sulphuric Acid Solution. Corros. Sci. 2010, 52, 1317–1325

(41)

El-Awady, A.A.; Abd-El-Nabey, B.A.; Aziz, S.G. Kinetic-thermodynamic and Adsorption Isotherms Analyses of the Inhibition of the Acid Corrosion of Steel by Cyclic and Open Chain Amines. J. Electrochem. Soc. 1992, 139, 2149–2154.

(42)

Abd El Rehim, S.S.; Ibrahim, A.M.; Khalid, K.F. The inhibition of 4-(20- amino-50methylphenylazo) Antipyrine on Corrosion of Mild Steel in HCl Solution. Mater. Chem. Phys. 2001, 70, 268–273.

(43)

Umoren, S. A.; Ebenso, E. E. Studies of the Anti – corrosive Effect of Raphia hookeri Exudates Gum – Halide Mixtures for Aluminium Corrosion in Acidic Medium. Pigm. Res. Technol. 2008, 37, 173 – 182.

(44)

Umoren, S. A.; Eduok, U. M.; Solomon, M. M. Effect of Polyvinylpyrrolidone – polyethylene Glycol Blends on the Corrosion Inhibition of Aluminium in HCl Solution. Pigm. Res. Technol. 2014, 43, 299 – 313.


Page 23 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


23 (45)

Gece, G. The Use of Quantum Chemical Methods in Corrosion Inhibitor Studies. Corros. Sci. 2008, 50, 2981 – 2992.

(46)

Gece, G. Theoretical Evaluation of the Inhibition Properties of two Thiophene Derivatives on Corrosion of Carbon Steel in Acidic Media. Mater. Corros. 2013, 64, 940 – 944.

(47)

Gece, G. Corrosion Inhibition Behavior of two Quinolone Chalcones: Insights from Density Functional Theory. Corros. Rev. 2015, 33, 195 – 202.

(48)

Chiter, F.; Lacaze-Dufaure, C.; Tang, H.; Pébèra, N. DFT Studies of the Bonding Mechanism of 8-Hydroxyquinoline and Derivatives on the (111) Aluminum Surface. Phys. Chem. Phys. 2015, 17, 22243 – 22258. Bardez, E.; Devol, I.; Larrey, B.; Valeur, B. Excited-state Processes in 8Hydroxyquinoline: Photoinduced Tautomerization and Solvation Effects. J. Phys. Chem. B 1997, 101, 7786 – 7793.

(49)

(50)

Castaneda, R.; Antal, S.A.; Draguta, S.; Timofeeva, T.V.; Khrustalev, V.N. Crystal Structure of 8-Hydroxyquinoline: A New Monoclinic Polymorph. Acta Cryst. 2014, E70, o924 – o925.

(51)

Koopmans, T. Über Die Zuordnung Von Wellenfunktionen Und Eigenwerten Zu Den Einzelnen Elektronen Eines Atoms. Physica 1934, 1, 104 – 113.

(52)

Sudheer; Quraishi, M. A. The Corrosion Inhibition Effect of Aryl Pyrazolo Pyridines on Copper in Hydrochloric Acid System: Computational and Electrochemical Studies. RSC Adv. 2015, 5, 41923 – 41933.

(53)

Pearson, R. G. Absolute Electronegativity and Hardness: Application to Inorganic Chemistry. Inorg. Chem. 1988, 27, 734 – 740.

(54)

Kayadibi, F.; Zor, S.; Sagdinc, S. G. Experimental and Theoretical Evaluation of the Inhibition Properties of Ketoprofen for the Corrosion of a Copper Surface in Hydrochloric Acid. Prot. Met. Phys. Chem. Surf. 2016, 52, 356 – 371.

(55)

Lukovits, I.; Kalman, E.; Zucchi, F. Corrosion Inhibitors – Correlation between Electronic Structure and Efficiency. Corrosion 2001, 57, 3 – 8.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 43

24

1. 2.

3.

4. 5.

Content Abstract Introduction Experimental 2.1 Materials 2.2 Electrochemical Measurements 2.3 Surface Morphological Studies 2.4 Quantum Chemical Calculations Results and Discussions 3.1 PDP Measurements 3.2 EIS Measurements 3.3 DEIS Measurements 3.4 Adsorption Consideration 3.5 Quantum Chemical Studies 3.6 Morphological Measurements Conclusions Acknowledgements References

Page 1 2 4 4 4 5 5 6 6 9 12 13 16 18 18 19 19

TABLES Table 1: Potentiodynamic polarization parameters for copper in 0.1 M HCl in the absence and presence of different concentrations of 8-HQ at 25 oC. Concentrations (8-HQ) No inhibitor

Ecorr Icorr 2 mV/Dec mV/Dec mV µA/cm 68 332 -147 63

Rp, Ω cm2 386

%IE -

0.004 M

70

210

-203

36

625

43

0.008 M

71

192

-216

21

1058

66

0.012 M

69

185

-237

17

1287

73

0.016 M

72

178

-251

15

1420

76


Page 25 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


25

Table 2: Electrochemical impedance parameters for copper in 0.1 presence of different concentrations of 8-HQ at 25 oC. n Rs Q Rct System 2 (Ω) (CPE) (0≤n≤1) (Ω.cm ) No inh 9.528 0.004028 0.450 212.8 0.004 M 8HQ 9.200 0.003496 0.492 405.4 0.008 M 8HQ 6.079 0.001620 0.511 648.8 0.012 M 8HQ 8.845 0.001562 0.535 892.4 0.016 M 8HQ 11.190 0.001141 0.557 1015


M HCl in the absence and W

%IE

0.006867 0.008778 0.010000 0.006028 0.005342

47 67 76 79


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 43

26

Table 3: Change of n, Rct and IE(%) values in blank solution and maximum concentration of inhibitor solution after 5, 10 and 15 h. (5h) (10h) (15h) Inhibitor Rct Rct Rct concentration IE(%) n IE(%) n IE(%) n 2 2 [Ωcm2] [Ωcm ] [Ωcm ] No inhibitor

0.51

277.00

-

0.56

327.00

-

0.58

412.00

-

0.016M 8-HQ

0.56

834.00

67

0.57

959.00

66

0.58

1070.00

62


Page 27 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48


27 Table 4: Adsorption parameters from Langmuir and El-Awady et al. Kinetic/thermodynamic isotherms for copper in 0.1 M HCl in the absence and presence of different concentrations of 8-HQ at 25 oC Langmuir El-Awady et al. Slope ( ) ( ) EIS 3.93 0.233 5.76 0.996 4.83 0.653 8.90 0.912 PDP 3.73 0.192 6.33 0.993 4.98 0.596 8.67 0.867

27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Page 28 of 43

28

Table 5: Selected geometric parameters for neutral form of 8-HQ in aqueous phase (for atom numbering scheme please see Figure 1). DFTa

Exp.b

H17 – O16

0.965

0.865

O16 – C2

1.363

1.358

C2 – C3

1.431

1.425

C3 – N18

1.362

1.367

N18 – C12

1.318

1.321

C2 – O16 – H17

109.5

109.6

C12 – N18 – C3

118.1

117.2

N18 – C12 – C11

123.9

123.9

N18 – C12 – H15

116.5

118.0

N18 – C3 – C2

119.2

118.0

C1 – C2 – C3

120.1

120.1

O16 – C2 – C1

122.7

119.2

O16 – C2 – C3

117.1

120.7

Parameters Bond lengths (Å)

Bond angles (°)

a

Calculated values at the B3LYP/6-311++G(d,p).

b

Ref.[50].

28


Page 29 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48


29

Table 6: The calculated quantum chemical descriptors at the B3LYP/6-311G++(d,p) basis set for 8-HQ in gas and aqueous phases. Compound

Phase a

EHOMO (eV)

ELUMO (eV)

∆E (EL-EH) (eV)

µ (D)

χ

η

∆N

8-HQ b

G

-6.123

-1.684

4.439

2.416

3.904

2.220

0.130

8-HQ c

A G A

-6.255 -10.703 -7.079

-1.837 -6.964 -3.213

4.418 3.739 3.866

3.598 1.855 2.863

4.046 8.834 5.146

2.209 1.870 1.933

0.098 -1.164 -0.172

a

G – gas phase (ε = 1.0), A – aqueous phase (ε = 78.5). Neutral form. c Protonated form.

b

29



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Page 30 of 43

30

30


Page 31 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


FIGURES

Figure 1



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 2


Page 32 of 43

Page 33 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

(b)

(c)

Figure 3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 4

0.1 M HCl

0.1 M HCl+0.016 M 8-HQ

Figure 5


Page 34 of 43

Page 35 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6

Figure 7



25

C/θ (X103)

20 15

EIS 10

PDP

5 0 4

8

12

16

C (mM)

Figure 8

0,7 0,6 0,5 0,4

Log (θ/1-θ)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

0,3 EIS

0,2

PDP

0,1

0 -0,1 -0,2 0.6

0.9

1,1

1,2

Log C (mM)

Figure 9


Page 36 of 43

Page 37 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 10



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

HOMO

Page 38 of 43

LUMO

(a)

(b)

Figure 11


Page 39 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(b)

(a)

(c)

Figure 12



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(a)


Page 40 of 43

Page 41 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(b)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(c)

Figure 13


Page 42 of 43

Page 43 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


FIGURE CAPTIONS Figure 1: Molecular structure of 8-hydroxyquinoline. Figure 2: Potentiodynamic polarization curves for copper in 0.1 M HCl in the absence and presence different concentrations of 8-HQ at 25 oC Figure 3: Impedance plots for low copper in 0.1 M HCl in the absence and presence different concentrations of 8-HQ at 25 oC in (a) Nyquist, (b) Bode modulus, and (c) phase angle formats. Figure 4: Equivalent circuit model used to fit Nyquist and DEIS experimental data. Figure 5:DEIS result of copper (a) without and (b) with 0.016 M 8-HQ in 0.1 M HCl Figure 6: Rct change of copper in 0.1 M HCl without and with 0.016 M 8-HQ Figure 7: Surface heterogeneity (n) of copper in 0.1 M HCl without and with 0.016 M 8-HQ Figure 8: Langmuir adsorption isotherm for 8-HQ in 0.1 M HCl at 25 oC from polarization and EIS measurements Figure 9: El-Awady et al. Kinetic/thermodynamic isotherm for 8-HQ in 0.1 M HCl at 25 oC from PDP and EIS measurements Figure 10:

FTIR spectra for 8-HQ before and after adding to 0.1 M HCl solutıon

Figure 11: Contour plots of the frontier molecular orbitals for (a) neutral and (b) protonated form of 8-HQ. Figure 12: SEM images for copper (a) in polished state, (b) exposed to 0.1 M HCl solution, (c) exposed to 0.1 M HCl solution containing 0.016 M 8-HQ and at 25 oC. Figure 13: EDAX spectrum for copper (a) in pure state, (b) exposed to 0.1 M HCl solution, (c) exposed to 0.1 M HCl solution containing 0.016 M 8-HQ and at 25 oC.


Experimental and Quantum Chemical Evaluation ... - ACS Publications

Recommend Documents