Experimental investigation on the corrosion inhibition of carbon steel by 5-(chloromethyl)-8-quinolinol hydrochloride in hydrochloric acid solution

Article abstract of DOI:10.1016/j.molliq.2016.03.056

5-(chloromethyl)-8-quinolinol hydrochloride (Cl-QH) was synthesized and characterized. Thus, its inhibition effect on XC38 steel corrosion in 1 M HCl medium was investigated using weight loss and electrochemical measurements. Polarization measurements indicated that, the studied compound acts as a mixed type inhibitor, the inhibition efficiency depends on its concentration and reaches 97% at 10^{- 3} M. Electrochemical impedance spectroscopy showed that the Cl-QH acts by the formation of a protective film at the metallic surface. The adsorption of the studied compound followed the Langmuir isotherm. So, scanning electronic microscopy (SEM) confirms the performance of Cl-QH against corrosion. In addition, quantum chemical calculations using DFT at the B3LYP/6-31G?level of theory was further used to calculate and discussed some electronic properties of the studied molecule. The theoretical and experimental results are in good agreement.

Full text of DOI:10.1016/j.molliq.2016.03.056

Journal of Molecular Liquids 219 (2016) 396–404
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Experimental investigation on the corrosion inhibition of carbon steel by
5
-(chloromethyl)-8-quinolinol hydrochloride in hydrochloric
acid solution
a
b
c
b
b,d
a
b
e,
M. El Faydy , M. Galai , A. El Assyry , A. Tazouti , R. Touir , B. Lakhrissi , M. Ebn Touhami , A. Zarrouk ⁎
a
Laboratoire d'Agroressources et Génie des Procédés, Université Ibn Tofail, Faculté des Sciences, Département de Chimie, B.P. 133, Kénitra, Morocco
Laboratoire d'Ingénierie des Matériaux et d'Environnement: Modélisation et Application, Faculté des Sciences, Université Ibn Tofail, BP 133, Kénitra 14 000, Morocco
Laboratoire d'Optoélectronique et de Physico-chimie des Matériaux, Université Ibn Tofail, Faculté des Sciences, Département de Physique, B.P. 133, Kénitra, Morocco
Centre Régional des Métiers de l'Education et de la Formation (CRMEF), Avenue Allal Al Fassi, Madinat Al Irfane BP, 6210 Rabat, Morocco
b
c
d
e
LCAE-URAC 18, Faculty of Science, First Mohammed University, PO Box 717, 60 000 Oujda, Morocco
a r t i c l e i n f o
a b s t r a c t
Article history:
5-(chloromethyl)-8-quinolinol hydrochloride (Cl-QH) was synthesized and characterized. Thus, its inhibition
effect on XC38 steel corrosion in 1 M HCl medium was investigated using weight loss and electrochemical
measurements. Polarization measurements indicated that, the studied compound acts as a mixed type inhibitor,
Received 5 September 2015
Received in revised form 17 March 2016
Accepted 20 March 2016
Available online xxxx
−3
the inhibition efficiency depends on its concentration and reaches 97% at 10 M. Electrochemical impedance
spectroscopy showed that the Cl-QH acts by the formation of a protective film at the metallic surface. The adsorp-
tion of the studied compound followed the Langmuir isotherm. So, scanning electronic microscopy (SEM)
confirms the performance of Cl-QH against corrosion. In addition, quantum chemical calculations using DFT at
the B3LYP/6–31G* level of theory was further used to calculate and discussed some electronic properties of the
studied molecule. The theoretical and experimental results are in good agreement.
Keywords:
XC38 Steel
Quinolinol dervivative
Corrosion inhibition
Weight loss
Electrochemical techniques
DFT
© 2016 Elsevier B.V. All rights reserved.
1
. Introduction
Acid solutions are widely used in industry, some of the important
Many research works have been developed in order to correlate the
substituent's effect and the inhibition efficiency of organic molecules
[13,14]. So, the quinolinol and its derivatives have received considerable
attention on their inhibition properties for metallic corrosion over the
past year [15,16]. They found that these compounds have fairly good
inhibiting properties for steel corrosion in acidic bath, and in some
fields of application being acid pickling of steel, chemical cleaning and
processing, ore production, and oil well acidizing. As acidic media,
hydrochloric acid is more economical, efficient, and trouble-free,
compared to other mineral acids [1]. However, iron and its alloys
could be corroded during these applications which result in a waste of
resources. So, the search and application for new and efficient corrosion
inhibitors becomes an obligation to prevent corrosion problems. The
selection of appropriate inhibitors mainly depends on the structure as
well as rational use in various environments. The majority of the
well-known inhibitors are organic compounds containing heteroatom,
such as O, N and/or S and multiple bonds, which allow an adsorption
on the metal surface [2–10]. In addition, the adsorption of these mole-
cules on metal surface is due to the presence of the substituents and
functional groups such as aromatic ring, π-conjugated system,
mesomeric and inductive effect and steric factors by physicochemical
interactions [11,12].
−
3
case the inhibition efficiency around 96% at 10 M and the inhibition
is of a mixed anodic-cathodic nature. Earlier reports [17] have been
shown that inhibition efficiency of organic compounds containing
heterocyclic nitrogen increases with the number of aromatic rings and
the availability of electronegative atoms in their structure.
In the other hand, quantum chemical calculations have been widely
used to study reaction mechanisms and to interpret the experimental
results as well as to resolve chemical ambiguities [18]. The remarkable
inhibition effect is reinforced by the presence of heteroatoms which
facilitates its adsorption on metallic surface and follows the sequence
O b N b S [19,20].
The aim of the present work is to study the inhibition efficiencies of
5-(chloromethyl)-8-quinolinol hydrochloride on steel XC38 corrosion
in 1 M HCl using weight loss and electrochemical measurements.
Invaluable quantum chemical parameters such as higher occupied mo-
lecular orbital (HOMO), lower unoccupied molecular orbital (LUMO),
⁎
Corresponding author.
E-mail address: azarrouk@gmail.com (A. Zarrouk).
http://dx.doi.org/10.1016/j.molliq.2016.03.056
167-7322/© 2016 Elsevier B.V. All rights reserved.
0

M. El Faydy et al. / Journal of Molecular Liquids 219 (2016) 396–404
397
Fig. 1. Synthesis of 5-chloromethyl-8-hydroxyquinoline hydrochloride (Cl-QH).
The H NMR, 13C NMR, IR and mass spectroscopy (ESI-MS) (Table 1)
were used to characterize and confirm the obtained product structure
(Supplementary data).
1
dipole momentum (μ) and total energy (TE) were obtained by DFT at
the B3LYP/6–31G* level of theory, help to understand the adsorption
properties by considering the structure of 5-(chloromethyl)-8-
quinolinol hydrochloride.
2.2. Weight loss measurements
2
. Experimental details
Weight loss measurements were carried out in glass beakers con-
taining 500 mL solution without and with different inhibitor concentra-
tions in 1 M HCl solution. The temperature of the solutions was held at
2
.1. Materials
298 K by a thermostat water bath. After 6 h of immersion in the acid so-
Steel XC38 containing in wt.%: 0, 37 C, 0.23 Si, 0.68 Mn, 0016 S, 0077
lutions in air without bubbling, the samples were taken out and were
−
4
Cr, 0011 Ti, 0059 Ni, 0009 Co, 0.16 Cu, and balance iron was used for
weight-loss and electrochemical tests. For weight loss measurements,
the rectangular coupons with the size of 5 cm × 1 cm × 0.1 cm were
used. A columned XC38 steel specimen, embedded in Teflon holder
cleaned carefully according to ASTM G-81 and reweighed to 10
g
for determining corrosion rate [22]. The inhibition efficiency is defined
as follows:
2
ω −ω
ω0
using epoxy resin with an exposed area of 1 cm , was used as the
0
ηω
¼
ꢀ 100
ð1Þ
working electrode for electrochemical measurements. The coupons and
electrodes were abraded with emery paper (up to 1200 grit), cleaned
with acetone and washed with distillated water, and finally dried at hot
air before being immersed in the acid solution. The aggressive solution
was prepared by dilution of an analytical grade HCl solution (37%) with
0
where ω and ω are the values of corrosion weight loss after immersion
in solution without and with inhibitor, respectively.
−
6
2.3. Electrochemical methods
distilled water. The concentration of inhibitors was ranged from 10
to 10 M. All assessments were carried out at temperature 298 K.
−
3
A saturated calomel electrode (SCE) was used as a reference elec-
trode and all potentials were given with it. The counter electrode was
a platinum plate of large surface area.
For the synthesis of 5-Chloromethyl-8-hydroxyquinoline hydrochlo-
ride (Cl-QH), all chemicals were purchased from Aldrich or Acros
(
France). The melting points were determined on an automatic electro-
1
In addition, the working electrode was immersed in the test solution
during half an hour until a steady state open circuit potential (Eocp) was
obtained. The steady-state polarization curves were recorded
potentiodynamically using a VoltaLab PGZ 100 and controlled by a
personal computer. The cathodic polarization curve was recorded by
polarization from Eocp to negative direction under potentiodynamic
thermal IA 9200 digital. The H NMR spectra were recorded on a Bruker
00 WB spectrometer at 300 MHz for solutions in Me SO-d . The chem-
3
2
6
ical shifts are given as δ values with reference to tetramethylsilane (TMS)
as internal standard and the infrared spectra were recorded from
−
1
−1
4
00 cm to 4000 cm on a Bruker IFS 66v Fourier transform spectrom-
eter using KBr pellets. The mass spectrum was recorded on THERMO
Electron DSQ II.
−
1
conditions corresponding to 1 mV s
(sweep rate) and under air
atmosphere. After this scan, the anodic polarization curve was recorded
by polarization from Eocp to positive direction under the same condi-
tions as said before. To evaluate corrosion kinetic parameters, a fitting
by Stern-Geary equation was used. To do so, the overall current density
values, i, were considered as the sum of two contributions, anodic and
So, the Cl-QH was synthesized according to the method described by
Fen et al. [21], which consists of the reaction of 8-hydroxyquinoline
with formaldehyde and concentrated HCl solution (Fig. 1).
Thus, a mixture of 10.0 g (0.068 mol) of 8-hydroxyquinoline, 11 ml
of concentrated hydrochloric acid, and 11 ml (0.397 mol) of 37% form-
aldehyde was treated with hydrogen chloride gas and stirred for 6 h.
The solution was allowed to stand at room temperature for 2 h without
stirring. The obtained yellow solid was collected on a filter, washed with
acetone, and dried under vacuum to afford 5-chloromethyl-8-
hydroxyquinoline hydrochloride (Cl-QH) (9.8 g, 98%) without further
a c
cathodic current i and i , respectively. For the potential domain not
too far from the open circuit potential, it may be considered that both
processes followed the Tafel law [23]. Thus, it can be derived from
Eq. (2):
i ¼ ia þ ic ¼ icorrf exp½ba ꢀ ðE−EcorrÞꢁ− exp½bc ꢀ ðE−EcorrÞꢁg
ð2Þ
f
purification, m.p.: 282 °C, R Value: 0.52 (n-hexane/acetone: 4/6).
Table 1
Spectral data of the synthesized compound.
Spectral data
IR (KBr, cm− ): 1600 (C = C quinoline), 2850–3000 (C-H quinoline), 3457 (O-H bonded), 1470–1490 (−CH
1
2
-).
1
H NMR (300 MHz, D
2
O-d
O-d
ESI-MS (m/z): 231 (75%), 195 (100%) (M ).
2
), δppm = 9.156–9.477 (s, 1H, quinoline-OH), 7.521–8.315 (m, 5H, quinoline), 5.030–5.267 (s, 2H, CH
2
-Cl).
1
3
C NMR (300 MHz, D
2
2
), δppm = 60.741 (quinoline-CH -Cl), 116.465, 122.356, 130.968, 142.800, 144.153(CH-quinoline); 128.863, 130.908, 144.237, 147.623 (C-quinoline).
2
+
1

398
M. El Faydy et al. / Journal of Molecular Liquids 219 (2016) 396–404
where icorr is the corrosion current density (A cm−2), b
and b are the
a c
−
1
Tafel constants of anodic and cathodic reactions (V ), respectively.
These constants are linked to the Tafel slopes β (V/dec) in usual
logarithmic scale given by Eq. (3):
ln10 2:303
β ¼
¼
ð3Þ
b
b
The corrosion parameters were then evaluated by means of
nonlinear least square method by applying Eq. (2) using Origin
software. However, for this calculation, the potential range applied
was limited to ± 0.100 V around Ecorr, else a significant systematic diver-
gence was sometimes observed for both anodic and cathodic branches.
The corrosion inhibition efficiency is evaluated from the corrosion
current densities values using the relationship (4):
0
i
−icorr
corr
ηPP
¼
ꢀ 100
ð4Þ
0
i
corr
Fig. 2. Evolution of open circuit potential (OCP) versus time for steel XC38 in 1 M HCl in the
−
6
−5
presence of Cl-QH at various concentrations. (1): 0 M (2): 10
10 M (5): 10 M (6): 5 × 10 M.
M (3): 10
M (4):
where i 0c orr and icorr are the corrosion current densities values without
and with inhibitor, respectively.
−4
−3
−3
The electrochemical impedance spectroscopy measurements were
carried out using a transfer function analyzer (VoltaLab PGZ 100),
with a small amplitude a.c. signal (10 mV rms), over a frequency
domain from 100 kHz to 100 mHz with five points per decade. The EIS
diagrams were done in the Nyquist representation. The results were
then analyzed in terms of an equivalent electrical circuit using EC-Lab
software. The inhibiting efficiency derived from EIS, ηEIS is also added
in Table 4 and calculated using the following Eq. (5):
3
. Results and discussion
3.1. Gravimetric study
The weight loss measurements are conducted in 1 M HCl solution at
98 K for 6 h of immersion time. The corrosion rate (Ωcorr), coverage
2
Ω
surface (θ) and inhibition efficiency (η ) values containing Cl-QH at dif-
ferent concentrations are given in Table 2. It is shown that the corrosion
rate of steel XC38 decreases and the inhibition efficiency increases with
increasing of concentration and reaches a maximum of 97% at 10 M of
Cl-QH.
Rct−R0
Rct
−3
ct
ηEIS
¼
ꢀ 100
ð5Þ
The corrosion inhibition by Cl-QH in 1 M HCl can be explained in
terms of the adsorption of its molecules on the metallic surface. This ad-
sorption was assumed to be a quasi-substitution process between water
molecules on the steel surface and the Cl-QH molecules which makes a
barrier for mass and charge transfer, and consequently, steel XC38 is
where R 0c t and Rct are the charge transfer resistance values in the absence
and presence of inhibitor, respectively.
2
.4. Scanning electron microscopy (SEM)
Ω
protected from aggressive acid solution. The increased η with the in-
Examination of steel XC38 specimens after exposure into 1 M solu-
creasing Cl-QH concentration indicates that more inhibitor molecules
are adsorbed on the steel surface leading to the formation of a protective
film [30,31].
tion, without and with 10−3 M of Cl-QH after a hold time immersion
of one day, was carried out using scanning electron microscopy (SEM;
JOEL JSM-5500). The energy of the acceleration beam employed was
2
0 KV.
2
.5. Computational chemistry
The quantum calculations were performed using the Gaussian 03
program [24]. The geometry of the studied compound was evaluated
using DFT level of the three-parameter compound functional of Becke
(
B3LYP) [25]. The 6–31G* basis set was used for all atoms [26–29].
The geometry structure was optimized under no constraint. The follow-
ing quantum chemical indices were considered: the energy of the
highest occupied molecular orbital (EHOMO), the energy of the lowest
unoccupied molecular orbital (ELUMO), the gap ΔEgap = EHOMO - ELUMO
,
the dipole moment (μ) and total energy (TE).
Table 2
Effect of Cl-QH concentration on corrosion data of steel XC38 in 1 M HCl.
Inhibitor
Blank
Conc. (M)
00
Ω
corr (mg/cm2 h)
η
Ω
(%)
θ
2.700
0.273
0.182
0.090
0.091
–
–
−
−
−
−
6
5
4
3
10
90
93
97
97
0.90
0.93
0.97
0.97
Cl-QH
10
1
1
0
0
Fig. 3. Potentiodynamic polarization curves of steel XC38 in 1 M HCl solution containing
different concentration of Cl-QH at 298 K.

M. El Faydy et al. / Journal of Molecular Liquids 219 (2016) 396–404
399
Table 3
Electrochemical parameters of steel XC38 in 1 M HCl solution in the presence of different
concentrations of Cl-QH.
Conc.
M)
-Ecorr
(mV/SCE)
i
corr
-β
c
β
a
θ
η
PP
(%)
(
(μA cm−2)
(mV dec−1)
(mV dec−1)
0
1
1
1
1
5
0
633
612
603
581
623
602
482.8
67.5
59.6
48.9
38.7
43.9
133.3
121.4
112.3
193.6
127.7
182.1
91.2
84.6
81.1
48.4
91.1
243.4
–
–
× 10−
6
5
4
3
3
0.86
0.88
0.89
0.92
0.91
86
88
89
92
91
−
−
−
−
× 10
× 10
× 10
× 10
3
3
.2. Potentiodynamic polarization curves
.2.1. Evolution of open circuit potential (OCP) versus time
Fig. 2 shows the open circuit potential (OCP) versus time at different
inhibitor concentration. It is noted that the potential for free-inhibitor
solution decreases gradually with time and stabilizes at value of -
6
14 mV/SCE after 30 min of immersion. This phenomenon characterizes
Fig. 5. Nyquist plots for steel XC38 in 1 M HCl solution in the absence and presence of
different concentrations of Cl-QH. Symbols: Experimental data, and Red lines: Fitting data.
the steel XC38 corrosion with a formation of corrosion products. So, in
the presence of Cl-QH, the potential stays stable with time.
be seen as a cathodic or anodic type, (ii) if displacement in E is
b85 mV/Ecorr, the inhibitor can be seen as mixed type. In our study,
the maximum displacement is b85 mV/Ecorr, which indicates that the
Cl-QH is a mixed type inhibitor.
3
.2.2. Polarization curves
Fig. 3 shows the potentiodynamic polarization curves for steel XC38
in 1 M HCl solution in the absence and presence of different concentra-
tions of Cl-QH. Their corresponding parameters such as icorr, Ecorr, β and
were evaluated from the experimental results using Eq. (2) and
a
c
However, the cathodic Tafel slopes (β ) change with the Cl-QH addi-
β
c
tion indicating a modification of the mechanism of cathodic hydrogen
evolution, which suggest that Cl-QH powerfully inhibits the corrosion
process of steel, and its ability as corrosion inhibitor is enhanced as its
concentration is increased. The suppression of cathodic process can be
due to the covering of the surface with monolayer due to the adsorbed
inhibitor molecules [34].
2
summarized in Table 3. In all cases, the correlation factor R is N0.999
indicating a reliable result. Fig. 4 shows, as for an example, the results
of regressions calculation for the cathodic and anodic scan in the pres-
ence of Cl-QH at various concentrations. It can be seen in this figure a
good agreement between the calculated and the experimental polariza-
tion data. These results show that the Cl-QH addition reduces both an-
odic metal dissolution and cathodic hydrogen evolution reactions. The
reduction of icorr is pronounced more and more with increasing inhibi-
tor concentration. The increased inhibition efficiency with inhibitor
concentration indicates that the tested compound acts by adsorption
on the metallic surface [32]. In addition, no definite change observed
in the corrosion potential (Ecorr). According to Riggs [33] and others
authors, if the displacement in E (i) is N85 mV/Ecorr, the inhibitor can
It can be seen, however, that compared to the blank case the value of
the anodic Tafel slopes (β ) are markedly changed in the presence of
a
Cl-QH, which suggests that Cl-QH can affect the kinetics of the anodic
process. From the structure of Cl-QH shown in Fig. 1, N atoms in the
quinolinol rings possess a number of lone pair of electrons. This may
favor the formation of Fe(II)– Cl-QH complex compound and thus
changes the dissolution mechanism of iron [35].
In addition, it is noted that the iron dissolution rate reduces
gradually with the presence of inhibitor at low anodic over-potentials
below – 450 mV/SCE and increases sharply when the applied potential
is screened to more anodic values. This potential is generally defined
as the desorption potential [36]. Therefore, it is concluded that, the
adsorption of the inhibitor molecules on metallic surface yields a layer
formation, which provides a good protection for the steel XC38 at low
anodic over-potentials. However, this film loses its performance at
high anodic potential regions. The observed behavior could be
explained by the significant iron dissolution, leading to desorption of
the layer formed from the metal surface.
Fig. 4. Narrow potential range polarization curves for steel XC38 in 1 M HCl solution in the
−
6
−5
presence of Cl-QH at various concentrations. (1): 0 M (2): 10
M (3): 10
M (4):
−
4
−3
−3
1
0
M (5): 10
M (6): 5 × 10
M. Symbols: Experimental data and Red lines:
Fig. 6. Electrical equivalent circuits used for modeling the metal/solution interface.
Fitting data.
(a) blank solution, 10− , 10 , 10 and 5 × 10 M of Cl-QH and (b) 10 M of Cl-QH.
6
−5
−4
−3
−3

400
M. El Faydy et al. / Journal of Molecular Liquids 219 (2016) 396–404
Table 4
Fitting results of EIS for steel XC38 in 1 M HCl in the absence and presence of different concentrations of Cl-QH at 298 K.
C
EOCP (mV/SCE)
R
s
R
a
C
a
n
a
R
ct
C
dl
τ
dl
n
dl
η
EIS
%
2
2
(μF cm−2)
2
(μF cm−2)
(M)
(Ω cm )
(Ω cm )
(Ω cm )
(ms)
0
1
1
1
1
5
0
−623
- 602
- 601
- 582
−616
−642
2.11 ± 0.36
2.16 ± 0.30
2.02 ± 0.25
2.21 ± 0.25
2.24 ± 0.28
2.15 ± 0.20
–
–
–
–
–
–
–
–
–
–
–
–
36.96 ± 2.53
205.3 ± 2.43
209.8 ± 2.46
233.7 ± 1.44
392.8 ± 3.94
365.5 ± 1.58
243.5 ± 0.69
119.8 ± 0.63
118.8 ± 0.86
113.6 ± 0.77
85.7 ± 0.63
101.9 ± 0.48
8.99 ± 0.001
0.74 ± 0.01
0.76 ± 0.01
0.77 ± 0.01
0.80 ± 0.01
0.82 ± 0.01
0.77 ± 0.01
–
× 10−
6
5
4
3
3
24.59 ± 0.002
24.92 ± 0.001
26.54 ± 0.001
33.66 ± 0.002
37.24 ± 0.001
82
82
84
91
90
−
−
−
−
× 10
× 10
× 10
× 10
20.19 ± 1.25
–
35.27 ± 0.10
–
0.87 ± 0.01
–
3
.3. Electrochemical Impedance Spectroscopy (EIS)
The representative Nyquist of steel XC38 electrode in 1 M HCl
Thus, the impedance of the CPE can be described by the following
equation:
Â
Ã
n
−1
solution in the absence and presence of various concentrations of
Cl-QH at corrosion potential is shown in Fig. 5. It is noted that the
Nyquist plot of steel XC38 in the absence and presence of 10 , 10
ZCPE ¼ QðjωÞ
ð6Þ
−
6
−5
where j is the imaginary number, Q is the frequency independent real
and 10− M of inhibitor contains a slightly depressed semi-circular
shape and only one time constant was appeared indicating that the
steel XC38 corrosion is mainly controlled by a charge transfer process.
In this case, the equivalent electric circuit, Fig. 6a, with one time con-
stants was proposed to reproduce these results by non linear regression
calculation.
4
−1
constant, Ω = 2πf is the angular frequency (rad s ), f is the frequency
of the applied signal, n is the CPE exponent for whole number of n = 1, 0,
−
1, CPE is reduced to the classical lump element-capacitor (C), resis-
tance (R) and inductance (L) [37]. The use of these parameters, similar
to the constant phase element (CPE), allowed the depressed feature of
Nyquist plot to be reproduced readily.
However, the effective calculated double layer capacitance (C) de-
rived from the CPE parameters according to the following equation [38]:
So, in the presence of 10− M of Cl-QH, the obtained impedance pre-
sented two separated loops. The one, at high frequency, was attributed
to the adsorbed species resistance due to the adsorption of the mole-
cules inhibitors and all other accumulated products. Conversely, the
one at low frequency can be attributed to the double layer capacitance
and the charge transfer resistance. In order to analyze this plot more
quantitatively, an equivalent electric circuit with two time constants
was tried to reproduce these results by non linear regression calcula-
tion. This circuit is shown in Fig. 6b.
It is worth pointing out that the application of an electrical circuit
consisting of double layer capacitor does not always enable achieving
satisfactory fitting to the experimental impedance data. The dispersion
of the impedance data can be attributed to the surface heterogeneity
resulting from the inhibitor's adsorption (mainly), surface roughness,
dislocations, impurities, grain boundaries, fractality, etc. In such case
using an equivalent electrical circuit employing the double layer
capacitance element is not a good enough approximation. The Constant
Phase Element (CPE) was suggested instead of Cdl. So, the more
heterogeneous surface, hence the higher n values, the greater deviation
from ideal capacitive behavior. It allows employing CPE element in
order to investigate the inhibitive film properties on metallic surface.
3
1
ð1−αÞ
α
α
C ¼ Q ꢀ R
ð7Þ
The most important data obtained from the equivalent circuit are
presented in Table 4. It may be remarked that Rct value increases and
C
dl decreases with inhibitor concentration until the optimum concen-
−
3
tration (10 M) indicating that more inhibitor molecules are adsorbed
on metallic surface and provided better surface coverage and/or en-
hanced the thickness of the protective layer at the metal/solution inter-
face [39].
In addition, it is shown that the ndl values increase from 0.74 to 0.82
with inhibitor concentration, which could be related to the decrease of
the surface heterogeneity as a result of the Cl-QH molecules adsorption
on steel XC38 surface and forming a uniform inhibitive film. In the same
way, the relaxation time constant (τdl) values increase with inhibitor
concentration as well and the time of adsorption process becomes
therefore much higher which means a slow adsorption process [40].
This shows that there is an agreement between the amount of charge
Table 5
Curve fitting results of inhibitor for different adsorption isotherms.
Isotherms
Langmuir
Linear forms
Curves
Parameters
R2
Values
Cinh
θ
1
Cinh ¼ f ðCinh
1
¼
þ Cinh
Þ
Kads
θ
K
ads(L mol−1)
7.26 × 105
1.08
Slope
1
2
Freundlich
Temkin
Inθ ¼ InKads þ n InCinh
θ ¼ 1 1nK þ 1 InC
1n(θ) = f(1n(Cinh))
θ = f(1n(Cinh))
R
0.9824
0.9767
0.00928
107.7
0.9811
1.008
K
ads(L mol−1)
Slope (1/n)
n
R
2
f
ads
f
inh
K
ads(L mol−1)
Slope (1/f)
0.00825
121.21
0.9654
9.62 × 10
12.04
0.9792
2.62 × 10
103.69
f
R
1nð θ Þ ¼ 1nðKadsÞ þ a ꢀ 1nð1−θÞ
1nð Þ ¼ f ð1nð1−θÞÞ
θ
2
Flory-Huggins
Frumkin
Cinh
Cinh
15
K
ads(L mol−1)
Slope (a)
1nðCinh ꢀ 1−θÞ ¼ −1nKads−2 ꢀ f ꢀ θ
1nðCinh ꢀ 1−θÞ ¼ f ðθÞ
R
2
θ
θ
43
K
ads(L mol−1)
Slope (−2f)
f
−51.84

M. El Faydy et al. / Journal of Molecular Liquids 219 (2016) 396–404
401
that can be stored (that is capacitance) and discharge velocity in the
interface (τdl) [41].
In the other hand, it is noted that the inhibition efficiencies values
obtained by the potentiodynamic polarization curve and electrochemi-
cal impedance spectroscopy were lower than those obtained by weight
loss measurements. This difference is probably due to the shorter
immersion time in the case of the electrochemical measurements.
3
.4. Adsorption considerations
Generally, the primary step in the inhibitors action in acidic
solutions is their adsorption onto metallic surface, which is usually
oxide-free. It has been reported that the inhibition mechanism of an in-
hibitor may vary with factors such as concentration, pH, the anion na-
ture the acid, and the metal nature [42]. So, the adsorption isotherm
type can provide additional information about the tested compounds
properties. For this, the coverage surface (θ), which determined from
ac impedance, polarization or weight loss measurements by the ratio
Ω
η /100, can be used. In this study, to make the fitting and select the suit-
Fig. 7. Langmuir adsorption plot of Cl-QH on steel XC38 in1 M HCl solution.
able isotherm, the coverage surface was estimated from polarization
measurements. So, the following adsorption isotherms are the most
common models to study the corrosion inhibition mechanism [43]:
Tempkinadsorptionisotherm expðf ꢀ θÞ ¼ Kads ꢀ Cinh
ð8Þ
ð9Þ
θ
−θ
Langmuiradsorptionisotherm
Frumkinadsorptionisotherm
¼ Kads ꢀ Cinh
1
θ
expð−2 ꢀ f ꢀ θÞ ¼ Kads ꢀ Cinh
−θ
ð10Þ
ð11Þ
1
1
=n
Freundlichadsorptionisothermθ ¼ Kads ꢀ Cinh
ꢀ
ꢁ
θ
Cinh
Flory–Hugginsadsorptionisotherm log
¼ logðKadsÞ þ a ꢀ logð1−θÞ
ð12Þ
where Kads is the equilibrium constant of the adsorption process, Cinh is
the inhibitor concentration, f is the factor of energetic inhomogeneity
and the parameter ‘a’ in Eq. (12) is the water molecules number
replaced by inhibitor molecules on metallic surface.
In this study, the Tempkin, Langmuir, Frumkin, Freundlich and
Flory–Huggins isotherm were fitted. The corresponding fitting curve re-
2
sults where r is the square of the correlation coefficient between the
dependent variables and the estimated values are shown in Table 5. It
is noted that the inhibitor was adsorbed on metallic surface according
to the Langmuir isotherm model (Fig. 7).
From the intercepts of the straight lines Cinh /θ vs. Cinh, the equilibri-
um constant values of the adsorption process, Kads can be determined.
⁎
This constant is related to the free energy of adsorption, ΔGads, by the
following equation [44]:
ꢀ
ꢁ
ꢂ
1
5:55
ΔG
ads
Kads ¼ 5
exp −
ð13Þ
RT
where 55,55 value represents the water concentration in solution by
−
1
mol L , R is the universal gas constant and T is the absolute
temperature.
In our case, ΔGads value of Cl-QH is about - 43.41 kJ mol−1. Its
⁎
negative value indicates that Cl-QH was strongly adsorbed on the steel
XC38 surface.
Generally, two modes of adsorption can be considered. Cl-QH
molecules are adsorbed on the metal surface due to the free electron
pairs on the oxygen and nitrogen atoms as well π-electrons of the
aromatic rings. It exists in the form of protonated species. If it is assumed
−
that Cl anions are firstly adsorbed onto metallic surface, the adsorption
Fig. 8. SEM micrographs of steel XC38 electrode surface after one day of immersion in 1 M
HCl solution: (a) the blank solution and (b) the presence of 10− M of Cl-QH.
3
of the cationic species would be limited by the content of these anions

402
M. El Faydy et al. / Journal of Molecular Liquids 219 (2016) 396–404
inhibitor molecules can be adsorbed on the steel XC38 surface and
protect it.
3.6. Theoretical calculations
Quantum chemical methods have already proven to be very useful in
determining the molecular structure as well as elucidating the electron-
ic structure and reactivity [49]. There were also utilized to establish
whether there is a clear relationship between the molecular structures
of inhibitor and its inhibition effect. So, the predicted properties of rea-
sonable accuracy can be obtained from density functional theory (DFT)
calculations [50,51]. The quantum chemical properties were obtained
after geometric optimization with respect to the all nuclear coordinates
using Kohn–Sham approach at DFT level. The optimized structure of Cl-
QH is shown in Fig. 9.
Generally, EHOMO is associated with the electron donating ability of a
molecule. High values of EHOMO are likely to indicate a tendency of the
molecule to donate electrons to appropriate acceptor molecules with
low-energy, empty molecular orbital. Therefore, the energy of the
ELUMO indicates the ability of the molecule to accept electrons; hence
Fig. 9. Optimized structure of the studied molecule obtained by B3LYP-6-31 G(d) method.
these are the acceptor states. Low values of ELUMO are to indicate a ten-
dency of the molecule to accept electrons [52]. As for the lower values of
ΔE (ELUMO - EHOMO) caused higher inhibition efficiency of Cl-QH [53].
This value is smaller by this obtained by F. Zhang et al. when they stud-
ied the corrosion inhibition of 2-(4-pyridyl)-benzimidazole for mild
steel in hydrochloric acid which is in the range of 4.43–6.26 eV [4].
In addition, as we know, frontier orbital theory is useful in predicting
the adsorption centers of the inhibitors responsible for the interaction
with surface metal atoms. The HOMO and the LUMO population of Cl-
QH were plotted and were shown in Fig. 10. It is noted that the LUMO
density is mainly localized on the Cl atom, while the HOMO density is
distributed around the entire molecule.
adsorption, the neutral species being adsorbed when possible on free
surface sites [45]. So, the hetero-cycle of Cl-QH may adsorb through
electrostatic interaction between the positively charged molecules and
the negatively charged metal surface. It has been observed that the ad-
sorption of ammonium compounds can be influenced by the nature of
anions [46,47]. The specific adsorption of anions having a smaller degree
of hydration such as chloride ions is expected to be more pronounced.
Being specifically adsorbed, they create an excess negative charge to-
wards the solution and favor more adsorption of the cations [48].
Moreover, Table 6 shows that Cl-QH has the highest EHOMO in the
neutral form (unprotonated molecule) such as mentioned in Fig. 9.
These results confirm those obtained by the experiments which indicate
that the interaction between Cl-QH and steel XC38 is electrostatically
(physisorption). In addition, the total energy of the Cl-QH is equal -
26422.348 eV indicating that is favorably adsorbed through the active
centers of adsorption. Lower values of dipole moment (μ) will favor
accumulation of the inhibitor in the metal surface layer and therefore
higher inhibition efficiency [54].
3
.5. Scanning electronic microscopy
Fig. 8 shows the scanning electronic microscopy (SEM) images of
steel XC38 surface immersed in 1 M HCl solution during one day in
the absence and presence of 10−3 M of Cl-QH. The image of the surface
exposed to the inhibitor-free aggressive solution (Fig. 8a), shows het-
erogeneous layer of corrosion products (appearance white clusters,
pits and cracks).
Moreover, the SEM image in the presence 10− M of Cl-QH (Fig. 8b)
shows a large area free of corrosion products (no pits or cracks except
polishing lines) and the surface became smooth. It is clear that, the
3
In addition, the relationship between electronic structures of Cl-QH
was deducted from the quantum chemical indices
E
HOMO
(−8.653 eV), ELUMO (−5.633 eV), ΔEgap (3.02 eV) and dipole moment
Fig. 10. The frontier molecule orbital density distributions of Cl-QH.

M. El Faydy et al. / Journal of Molecular Liquids 219 (2016) 396–404
403
[
11] K.F. Khaled, The inhibition of benzimidazole derivatives on corrosion of iron in 1 M
HCl solutions, Electrochim. Acta 48 (17) (2003) 2493–2503.
12] M. Abdallah, Corrosion behaviour of 304 stainless steel in sulphuric acid solutions
μ (1.1188 D) of the inhibitor. The high inhibition efficiency of Cl-QH can
be attributed to the high value of EHOMO, dipole moment μ and low value
of ELUMO. The results seem to indicate, that charge transfer from Cl-QH
takes place during adsorption at the steel XC38 surface. High value of
[
and its inhibition by some substituted pyrazolones, Mater. Chem. Phys. 82 (3)
(2003) 786–792.
[
13] M.A. Hegazy, S.M. Rashwan, M.M. Kamel, M.S. El Kotb, Synthesis, surface properties
and inhibition behavior of novel cationic gemini surfactant for corrosion of carbon
steel tubes in acidic solution, J. Mol. Liq. 211 (2015) 126–134.
EHOMO may facilitate adsorption (and therefore inhibition) by influenc-
ing the transport process through the adsorbed layer [55]. These obtain-
ed results are in good agreement to those obtained by experimental
studies.
[14] D. Ben Hmamou, R. Salghi, A. Zarrouk, H. Zarrok, R. Touzani, B. Hammouti, A. El
Assyry, Investigation of corrosion inhibition of carbon steel in 0.5 M H2SO4 by
new bipyrazole derivative using experimental and theoretical approaches, J. Envi-
ron, Chem. Eng. 3 (2015) 2031–2041.
4
. Conclusion
[15] Eno E. Ebenso, Ime B. Obot, L.C. Murulana, Quinoline and its Derivatives as Effective
Corrosion Inhibitors for Mild Steel in Acidic Medium, Int. J. Electrochem. Sci. 5
(
2010) 1574–1586.
The corrosion inhibition of steel XC38 in 1 M HCl solution by Cl-QH
was studied using weight loss and electrochemical techniques. Accord-
ing to experimental findings, it could be concluded that:
[
[
[
16] Y. Abboud, A. Abourriche, T. Saffaj, M. Berrada, M. Charrouf, A. Bennamara, H.
Hannache, A novel azo dye, 8-quinolinol-5-azoantipyrine as corrosion inhibitor
for mild steel in acidic media, Desalination 237 (2009) 175–189.
17] F. Bentiss, M. Traisnel, L. Gengembre, M. Lagrenée, A new triazole derivative as in-
hibitor of the acid corrosion of mild steel: electrochemical studies, weight loss de-
termination, SEM and XPS, Appl. Surf. Sci. 152 (1999) 237–249.
18] F.E. Awe, S.O. Idris, M. Abdulwahab, E.E. Oguzie, Theoretical and experimental inhib-
itive properties of mild steel in HCl by ethanolic extract of Boscia senegalensis, Co-
gent Chem. 1 (2015) 1112676, http://dx.doi.org/10.1080/23312009.2015.1112676.
[19] F. Benhiba, H. Zarrok, A. Elmidaoui, M. El Hezzat, R. Touir, A. Guenbour, A. Zarrouk, S.
Boukhris, H. Oudda, Theoretical prediction and experimental study of 2-phenyl-1, 4-
dihydroquinoxaline as a novel corrosion inhibitor for carbon steel in 1.0 HCl, J.
Mater. Environ. Sci. 6 (8) (2015) 2301–2314.
20] A.B. Tadros, A.B. Adbennabey, Inhibition of the acid corrosion of steel by 4-amino-3-
hydrazino-5-thio-1,2,4-triazoles, J. Electroanal. Chem. 24 (1988) 433.
21] L. Feng, X. Wang, Z. Chen, Study on the noncovalent complexes of ginsenoside and
cytochrome by electrospray ionization mass spectrometry, Spectrochim. Acta, Part
A 71 (2008) 312–316.
[22] ASTM G-81, Annual Book of ASTM Standards, 1995.
23] M. Stern, A.L. Geary, Electrochemical polarization: A theoretical analysis of the shape
of polarization curves, J. Electrochem. Soc. 104 (1957) 56–63.
24] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, GAUSSIAN 03, Revi-
sion B.04, Gaussian, Inc., Pittsburgh PA, 2003 and al.
1
. Cl-QH is a good corrosion inhibitor for steel XC38 in 1 M HCl solution
and its performance depends on its concentration and reaches a
−
3
maximum of 92% at 10 M.
2
3
. Cl-QH acts as a mixed type inhibitor.
. The high inhibition efficiency of the inhibitor was explained by
adsorption of Cl-QH molecules on steel XC38 surface.
. The EIS measurements indicate the formation of a protective film at
the metallic surface.
. The adsorption of Cl-QH on steel XC38 surface obeys the Langmuir
adsorption isotherm.
. Scanning electronic microscopy confirms the performance of Cl-QH
against corrosion.
. The theoretical and experimental results are in a good agreement.
4
5
6
7
[
[
[
[
[
[
25] A.D. Becke, Density-functional thermochemistry. III. The role of exact exchange, J.
Acknowledgements
Chem. Phys. 98 (1993) 5648–5652.
26] J.S. Binkley, J.A. Pople, W.J. Hehre, Self-consistent molecular orbital methods. 21.
Small split-valence basis sets for first-row elements, J. Am. Chem. Soc. 102 (1980)
The authors thankful to the Centre for Analysis and Research of the
University Ibn Tofaïl Morocco and to the Unit of Support for Technical
and Scientific Research of the National Centre of Scientific and Technical
Research (UATRS, CNRST-Morocco) for chemical analysis.
9
39–947.
[
[
[
27] K.D. Dobbs, W.J. Hehre, Molecular orbital theory of the properties of inorganic and
organometallic compounds 4. Extended basis sets for third-and fourth-row, main-
group elements, J. Comput. Chem. 7 (1986) 359–378.
28] W.J. Pierto, M.M. Francl, W.J. Hehre, D.J. Defrees, J.A. Pople, J.S. Binkley, Self-
consistent molecular orbital methods. 24. Supplemented small split-valence basis
sets for second-row elements, J. Am. Chem. Soc. 104 (1982) 5039–5048.
29] K.D. Dobbs, W.J. Hehre, Molecular orbital theory of the properties of inorganic and
organometallic compounds. 6. Extended basis sets for second-row transition metals,
J. Comput. Chem. 8 (1987) 880–893.
[30] V.S. Rao, L.K. Singhal, Corrosion behavior and passive film chemistry of 216 L stain-
less steel in sulphuric acid, J. Mater. Sci. 44 (2009) 2327–2333.
[31] A. Zarrouk, B. Hammouti, A. Dafali, F. Bentiss, Inhibitive properties and adsorption of
purpald as a corrosion inhibitor for copper in nitric acid medium, Ind. Eng. Chem.
Res. 52 (2013) 2560–2568.
References
[
1] D.D.N. Singh, T.B. Singh, B. Gaur, The role of metal cations in improving the inhibitive
performance of hexamine on the corrosion of steel in hydrochloric acid solution,
Corros. Sci. 37 (1995) 1005–1019.
2] B. Zerga, B. Hammouti, M. Ebn Touhami, R. Touir, M. Taleb, M. Sfaira, M. Bennajeh, I.
Forssal, Comparative inhibition study of new synthesised pyridazine derivatives to-
wards mild steel corrosion in hydrochloric acid. Part-II: Thermodynamic Proprieties,
Int. J. Electrochem. Sci. 7 (2012) 471–483.
[
[
[
3] K. Adardour, R. Touir, Y. Ramli, R.A. Belakhmima, M. Ebn Touhami, C. Kalonji
Mubengayi, H. El Kafsaoui, E.M. Essassi, Comparative inhibition study of mild steel
corrosion in hydrochloric acid by new class synthesised quinoxaline derivatives:
part I, Res. Chem. Intermed. 39 (2013) 1843–1855.
4] H. Zarrok, A. Zarrouk, R. Salghi, M. Ebn Touhami, H. Oudda, B. Hammouti, R. Touir, F.
Bentiss, S.S. Al-Deyab, Corrosion inhibition of C38 steel in acidic medium using N-1-
naphthylethylenediamine dihydrochloride monomethanolate, Int. J. Electrochem.
Sci. 8 (2013) 6014–6032.
[32] O. Nnabuk, Eddy, experimental and theoretical studies on some amino acids and
their potential activity as inhibitors for the corrosion of mild steel: part 2, J. Adv.
Res. 2 (2011) 35–47.
[33] O.L. Riggs Jr., Corrosion Inhibition, second ed. Nathan C.C., Houston TX, 1973.
[34] Y. Abbouda, A. Abourriche, T. Saffaj, M. Berrada, M. Charrouf, A. Bennamara, N. Al
Himidi, H. Hannache, 2,3-quinoxalinedione as a novel corrosion inhibitor for mild
steel in 1 M HCl, Mater. Chem. Phys. 105 (2007) 1–5.
[35] Fan Zhang, Yongming Tang, Ziyi Cao, Wenheng Jing, Zhenglei Wu, Yizhong Chen,
Performance and theoretical study on corrosion inhibition of 2-(4-pyridyl)-benz-
imidazole for mild steel in hydrochloric acid, Corros. Sci. 61 (2012) 1–9.
[36] A. Zarrouk, H. Zarrok, R. Salghi, B. Hammouti, F. Bentiss, R. Touir, M. Bouachrine,
Evaluation of N-containing organic compound as corrosion inhibitor for carbon
steel in phosphoric acid, J. Mater. Environ. Sci. 4 (2013) 177–192.
[37] H. Gerengi, K. Darowicki, G. Bereket, P. Slepski, Evaluation of corrosion inhibition of
brass-118 in artificial seawater by benzotriazole using dynamic EIS, Corros. Sci. 51
(2009) 2573–2579.
[38] G.J. Brug, A.L.G. Van Den Eeden, M. Sluyters-Rehbach, J.H. Sluyters, The analysis of
electrode impedances complicated by the presence of a constant phase element, J.
Electroanal. Chem. 176 (1984) 275–295.
[39] M. Moradi, J. Duan, X. Du, Investigation of the effect of 4,5-dichloro-2-n-octyl-4-
isothiazolin-3-one inhibition on the corrosion of carbon steel in Bacillus sp. inocu-
lated artificial seawater, Corros. Sci. 69 (2013) 338–345.
[40] A. Popova, M. Christov, A. Vasilev, Mono- and dicationic benzothiazolic
quaternary ammonium bromides as mild steel corrosion inhibitors. Part II:
Electrochemical impedance and polarisation resistance results, Corros. Sci. 53
(2011) 1770–1777.
[41] K.F. Khaled, M.M. Al-Qahtani, The inhibitive effect of some tetrazole derivatives
towards Al corrosion in acid solution: chemical, electrochemical and theoretical
studies, Mater. Chem. Phys. 113 (2009) 150–158.
[
[
[
[
5] R. Solmaz, Investigation of adsorption and corrosion inhibition of mild steel in hy-
drochloric acid solution by 5-(4-dimethylaminobenzylidene)rhodanine, Corros.
Sci. 79 (2014) 169–176.
6] R. Touir, R.A. Belakhmima, M. Ebn Touhami, L. Lakhrissi, M. El Fayed, B. Lakhrissi,
E.M. Essassi, Comparative inhibition study of mild steel corrosion in hydrochloric
acid by benzimidazole derivatives, J. Mater. Environ. Sci. 4 (6) (2013) 921–930.
7] J. Hmimou, A. Rochdi, R. Touir, M. Ebn Touhami, E.H. Rifi, A. El Hallaoui, A. Anouar, D.
Chebab, Study of corrosion inhibition of mild steel in acidic medium by 2-propargyl-
5-p-hlorophenyltetrazole: part I, J. Mater. Environ. Sci. 3 (3) (2012) 543–550.
8] Y. Elkacimi, M. Achnin, Y. Aouine, M. Ebn Touhami, A. Alami, R. Touir, M. Sfaira, D.
Chebabe, A. Elachqar, B. Hammouti, Inhibition of mild steel corrosion by some
phenyltetrazole substituted compounds in hydrochloric acid, Port. Electrochim.
Acta 30 (2012) 53–65.
[
9] T. Ghailane, R.A. Balkhmim, R. Ghailane, A. Souizi, R. Touir, M. Ebn Touhami, K.
Marakchi, N. Komiha, Experimental and theoretical studies for mild steel corrosion
inhibition in 1 M HCl by two new benzothiazine derivative, Corros. Sci. 76 (2013)
317–324.
[
10] A. Bousskri, A. Anejjar, M. Messali, R. Salghi, O. Benali, Y. Karzazi, S. Jodeh, M.
Zougagh, E.E. Ebenso, B. Hammouti, Corrosion inhibition of carbon steel in aggres-
sive acidic media with 1-(2-(4-chlorophenyl)-2-oxoethyl)pyridazinium bromide,
J. Mol. Liq. 211 (2015) 1000–1008.

404
M. El Faydy et al. / Journal of Molecular Liquids 219 (2016) 396–404
[
[
[
42] H.D. Leçe, K.C. Emregül, O. Atakol, Difference in the inhibitive effect of some Schiff
base compounds containing oxygen, nitrogen and sulfur donors, Corros. Sci. 50
[49] E. Kraka, D. Cremer, Computer design of anticancer drugs, J. Am. Chem. Soc. 122
(2000) 8245–8264.
[50] C. Adamo, V. Barone, A TDDFT study of the electronic spectrum of s-tetrazine in the
gas-phase and in aqueous solution, Chem. Phys. Lett. 330 (2000) 152–160.
[51] M. Parac, S. Grimme, Comparison of multireference Møller − plesset theory and
time-dependent methods for the calculation of vertical excitation energies of mole-
cules, J. Phys. Chem., A 106 (2003) 6844–6850.
(2008) 1460–1768.
43] R. Touir, M. Ebn Touhami, B. Lakhrissi, Mild steel corrosion inhibition in 200 ppm
NaCl by new surfactant, LAP LAMBRT Acadimic Publishing, Saarbrucken, 2014
Deutschland/Germany.
44] E. Khamis, F. Bellucci, R.M. Latanision, E.S.H. El-Ashry, Acid corrosion inhibition of
nickel by 2-(triphenosphoranylidene) succinic anhydride, Corrosion 47 (1991)
[52] G. Gece, The use of Quantum Chemical methods in corrosion inhibitor studies,
677–686.
Corros. Sci. 50 (2008) 2981–2992.
[
[
[
[
45] E. Blomgren, J.O'.M. Bockris, The Adsorption of Aromatic Amines at the Interface:
Mercury-Aqueous Acid Solution, J. Phys. Chem. 63 (1959) 1475–1484.
46] S. Rengamani, S. Muralidharan, M. Anbu Kulandainathan, S. Venkatakrishan Iyer, J.
Appl. Electrochem. 24 (1994) 355–360.
47] Z.A. Foroulis, Procceding of the Sixth European Symposium on Corrosion Inhibitors,
vol. 81985 130 Ferrara.
48] Z.A. Iofa, G.N. Thomashov, Zh. Fiz. Khim., 34 (1960) 1036.
[53] R.M. Issa, M.K. Awad, F.M. Atlam, Quantum Chemical studies on the inhibition of
corrosion of copper surface by substituted uracils, Appl. Surf. Sci. 255 (2008)
2433–2441.
[54] N. Khalil, Quantum Chemical approach of corrosion inhibition, Electrochim. Acta 48
(2003) 2635–2640.
[55] I. Lukovits, E. Kalman, I. Bako, I. Felhosi, J. Telegdi, Proc. Eighth European Symposium
on Corrosion inhibitors, Ann. Univ. Ferrara, N. S., Sez. V 10 (1995) 543 \.