Effect of OH, NH2 and OCH3 groups on the corrosion inhibition efficacy of three new 2,4,5-trisubstituted imidazole derivatives on mild steel in acidic solutions: Experimental, surface and DFT explorations

Article abstract of DOI:10.1016/j.molliq.2021.115587

Three new imidazole derivatives namely,4-(4,5-bis(4-methoxyphenyl)-1H-imidazol-2-yl)phenol (IM₁), 4-(4,5-bis(4-methoxyphenyl)-1H-imidazol-2-yl)benzenamine (IM₂), 2,4,5-tris(4-methoxy phenyl)-1H-imidazole (IM₃) were synthesized using microwave irradiation method. The noteworthy highlights of this method are safe reaction profiles, broad substrate scope, short run time, catalyst-free, excellent yields, economical, solvent-free, and simple workup conditions. The structural characterization of all the imidazole derivatives has been confirmed by ¹HNMR and mass spectral techniques. The corrosion inhibition potential of all the imidazoles was explored using weight loss and electrochemical methods. The imidazole derivative (IM₁) bearing a hydroxyl group exhibited maximum corrosion inhibition efficiency compared to other imidazoles (up to 96%). Strong adsorption of studied imidazole molecules followed the Langmuir model with very good correlation coefficients. The calculated Gibbs free energy of adsorption values suggested the mixed type of adsorption (physisorption and chemisorption). The polarization measurements indicated studied imidazole derivatives as mixed types of corrosion inhibitors. Further, scanning electron microscopy (SEM), XPS and XRD were performed to study the surface morphology of Mild steel (MS) surface. Quantum chemical calculations (DFT) was used to prove the obtained inhibition efficiencies (η %).

Full text of DOI:10.1016/j.molliq.2021.115587

Journal of Molecular Liquids 329 (2021) 115587
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Effect of OH, NH2 and OCH3 groups on the corrosion inhibition efficacy of
three new 2,4,5-trisubstituted imidazole derivatives on mild steel in
acidic solutions: Experimental, surface and DFT explorations
a
c
d
b
M.K. Prashanth a, C.B. Pradeep Kumar b, , B.S. Prathibha , M.S. Raghu , K. Yogesh Kumar , M.B. Jagadeesha ,
⁎
K.N. Mohana e, Honnur Krishna f
a
Dept of Chemistry, BNM Institute of Technology, Bangalore 560070, India
Dept of Chemistry, Malnad College of Engineering, Hassan 573202, India
Dept of Chemistry, New Horizon College of Engineering, Bangalore 560103, India
Department of Chemistry, Jain University, Ramanagara, 562112, Bangalore, India
b
c
d
e
Dept of Studies in Chemistry, University of Mysore, Manasagangothri, Mysuru 570006, India
f
Department of Chemistry, S.D.V.S. Sangh's S. S. Arts College T.P. Science Institute, Sankeshwar, Belagavi, Karnataka 591313, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Three new imidazole derivatives namely,4-(4,5-bis(4-methoxyphenyl)-1H-imidazol-2-yl)phenol (IM1), 4-(4,5-
bis(4-methoxyphenyl)-1H-imidazol-2-yl)benzenamine (IM2), 2,4,5-tris(4-methoxy phenyl)-1H-imidazole
(IM3) were synthesized using microwave irradiation method. The noteworthy highlights of this method are
safe reaction profiles, broad substrate scope, short run time, catalyst-free, excellent yields, economical,
solvent-free, and simple workup conditions. The structural characterization of all the imidazole derivatives has
been confirmed by 1HNMR and mass spectral techniques. The corrosion inhibition potential of all the imidazoles
was explored using weight loss and electrochemical methods. The imidazole derivative (IM1) bearing a hydroxyl
group exhibited maximum corrosion inhibition efficiency compared to other imidazoles (up to 96%). Strong ad-
sorption of studied imidazole molecules followed the Langmuir model with very good correlation coefficients.
The calculated Gibbs free energy of adsorption values suggested the mixed type of adsorption (physisorption
and chemisorption). The polarization measurements indicated studied imidazole derivatives as mixed types of
corrosion inhibitors. Further, scanning electron microscopy (SEM), XPS and XRD were performed to study the
surface morphology of Mild steel (MS) surface. Quantum chemical calculations (DFT) was used to prove the ob-
tained inhibition efficiencies (η %).
Received 16 December 2020
Received in revised form 27 January 2021
Accepted 2 February 2021
Available online 5 February 2021
Keywords:
Mild steel
Imidazoles
Electrochemical impedance spectroscopy
SEM
XPS
DFT
QC
© 2021 Elsevier B.V. All rights reserved.
1. Introduction
Metals destruction can be lowered by using many methods. Using a
small amount of organic compounds as inhibitors is a method exhibit
The study of corrosion and its inhibition is currently one of the most
active fields to protect metals from various corrosive environments
[1–3]. Mild steel (MS) is widely used in many industries because of its
excellent structural and mechanical properties. MS also has many draw-
backs i.e., degradation and corrosion in various acidic environments.
However different acidic and basic solutions are extensively used in
many chemical and petrochemical industries for effective acid pickling
treatment. The major consequence of the pickling process is in addition
to removing unwanted scales, acids cause significant damage to MS sub-
strate. Hence, the demand for reducing the rate of corrosion and method
development for the prevention of corrosion is high across the globe.
desirable practical application through which the rate of corrosion can
be controlled. Generally, organic compounds containing π - electrons
(N, S, and O) and different hetero atoms acts as efficient inhibitors in dif-
ferent aggressive solutions because of their strong adsorptive ability on
the metal surface [4].
Several authors reported many organic compounds as corrosion
inhibitors in different environments [5–9]. Studies have also demon-
strated the rate of corrosion can be prevented by forming donor-
acceptor complexes of inhibitor and metal surface. Thus, corrosion
protection efficiency is directly proportional to functional groups, elec-
tron density, and electronic structure of inhibitor molecules [10–12].
In this connection, organic compounds containing imidazole moiety
are the effective inhibitors for different metals in a different medium.
Many imidazoles and its derivatives have been reported as excellent
corrosion inhibitors in the different mediums [13–21]. Also, imidazole
⁎
Corresponding author at: Dept of Chemistry, Maland College of Engineering, Hassan
573202, India.
E-mail address: pradp12@gmail.com (C.B.P. Kumar).
https://doi.org/10.1016/j.molliq.2021.115587
0167-7322/© 2021 Elsevier B.V. All rights reserved.

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Table 1
Optimization of reaction parameters.
Entry
NH4OAc (mmol)
Temp (°C)
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
1
1
1
1
1
2
2
2
2
2
2
3
100
100
100
110
120
100
100
100
110
110
120
110
5
8
10
10
10
5
63
68
72
76
77
71
79
84
93
93
93
93
8
10
10
12
10
10
9
10
11
12
contains 2 to 3 hetero atoms, therefore it is worth investigating the cor-
rosion inhibition efficiency. Other important characteristic features of
imidazole and its derivatives are low cost and low toxicity as reported
in the literature [22]. For many years imidazole represents eco-
friendly corrosion inhibitors for many substrates and belongs to the
class of nitrogen-containing organic compounds with greater inhibition
potential due to the high electron density around the nitrogen atoms
[23].
A thought-provoking task has been the hunt for a creative key for the
reduction reaction time, by products, workup procedure and increased
yield in organic process. This can be resovled by carrying out the reac-
tion in microwave condition. For accelerated organic synthesis,
microwave-assisted synthesis has a significant effect on the synthetic
organic chemist to prevent side product development. To date, numer-
ous traditional methods for imidazole synthesis have been reported in
the literature [24–28]. However, it was mentioned that all these ap-
proaches include several drawbacks such as tedious workup procedure,
prolonged reaction time, poor yields, and use of expensive and environ-
mentally toxic organic reagents or catalyst or solvent. We have there-
fore developed an ecofriendly, efficient, catalyst and solvent free
method for the synthesis of imidazoles.
In the present work authors used three newly designed imidazole
derivatives namely, 4-(4,5-bis(4-methoxyphenyl)-1H-imidazol-2-yl)
phenol (IM1), 4-(4,5-bis(4-methoxyphenyl)-1H-imidazol-2-yl)
benzenamine (IM2), 2,4,5-tris(4-methoxyphenyl)-1H-imidazole (IM3)
to evaluate corrosion inhibition efficiency on MS in HCl medium. To
evaluate the inhibition efficiency both electrochemical (EIS & Potentio-
dynamic polarization) and gravimetric methods are used. Suitable ad-
sorption isotherm was proposed, and thermodynamic parameters are
calculated and reported. Surface morphology of MS surface (inhibited
& uninhibited) has been evaluated using scanning electron microscopy
(SEM), X-Ray Diffraction (XRD), and X-Ray photoelectron (XPS)
techniques.
the remaining is iron. The specimens under study are abraded by
using various grades SiC emery papers, then the MS specimen is washed
with demineralized water and finally dried by using tissue paper after
those MS specimens are immersed for 10 S in acetone and dried out
later placed in desiccators. After the completion of weight loss experi-
ments, the MS coupons were rinsed with acetone and weighed. Electro-
chemical measurements were performed by exposing an MS surface
area of 1 cm3 (1 cm2 surfaces was exposed by covering the MS surface
by using epoxy resin). The calculated quantities of the imidazole deriv-
atives were used to prepare the concentration of different inhibitors.
2.2. Synthesis of inhibitors
2.2.1. General procedure for the synthesis of 2,4,5-trisubstituted imidazole
derivatives (3a-c)
The mixture of 4,4′-dimethoxybenzil (1 mmol), aromatic aldehyde
(1 mmol), and ammonium acetate (2 mmol) were transferred to a
clean and dry mortar, triturated to form a uniform mixture. The
resulting mixture was then transferred to a 10 mL microwave vessel
and it was heated at 110 °C using microwave irradiation (300 W) for
10 min. The reaction was monitored by TLC (hexane: ethyl acetate
7:3 v/v) and the products were allowed to cool to room temperature.
The resulting residue was directly purified by column chromatography
using hexane: ethyl acetate 7:3 v/v as eluent.
2.2.2. Synthesis of 4-(4,5-bis(4-methoxyphenyl)-1H-imidazol-2-yl)phenol
(3a, IM1)
mp.: 271 °C.Anal.calc. For C23H20N2O3: C, 74.18; H, 5.41; N, 7.52.
found: C, 74.06; H, 5.35; N, 7.43. 1H NMR (400 MHz, DMSO‑d6) δ: 3.73
(s, 6H, (-OCH3)2), 5.22 (s, 1H, -OH), 7.33–7.75 (m, 12H, Ar\\H), 12.32
(s, 1H, -NH).MS, m/z: 373 (M + 1).
2. Experimental
2.2.3. Synthesis of 4-(4,5-bis(4-methoxyphenyl)-1H-imidazol-2-yl)aniline
(3b - IM2)
2.1. Materials
mp.: 274 °C.Anal.calc. For C23H21N3O2: C, 74.37; H, 5.70; N, 11.31.
found: C, 74.31; H, 5.62; N, 11.39. 1H NMR (400 MHz, DMSO‑d6) δ:
3.73 (s, 6H, (-OCH3)2), 6.47 (s, 2H, -NH2), 7.03–7.88 (m, 12H, Ar\\H),
12.50 (s, 1H, -NH). MS, m/z: 372 (M + 1).
The chemical composition of the studied MS coupon is as follows
(wt%): Si-0.023, S- 0.023, C-0.051, Mn-0.179, Al-0.103, P 0.005, and
2

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Table 2
Substrate scope of the reaction.
Compound
IM1 (3a)
R
Product
Yield (%)
93
IM2 (3b)
91
IM3 (3c)
90
2.2.4. Synthesis of 2,4,5-tris(4-methoxyphenyl)-1H-imidazole (3c)
polarization measurements. By using Tafel plots, the corrosion current
mp.: 286 °C. Anal.calc. For C24H22N2O3: C, 74.59; H, 5.74; N, 7.25.
found: C, 74.48; H, 5.69; N, 7.18. 1H NMR (400 MHz, DMSO‑d6) δ: 3.76
(s, 9H, (-OCH3)3), 7.04–7.50 (m, 12H, Ar\\H), 12.58 (s, 1H, -NH). MS,
m/z: 387 (M + 1).
density (icorr) was evaluated.
2.3.2. Mass loss measurements
0.5 M HCl solution was used to immerse the 2 × 2 × 0.1 cm dimen-
sion MS sample. To this, different concentrations of the imidazole deriv-
atives were added and after 6 h, the corrosion rate (CR) and inhibition
efficiency (EWL %) are calculated using eqs. (1) and (2).
2.3. Methods
2.3.1. Electrochemical techniques
ΔW
St
CR
¼
ð1Þ
ð2Þ
All the electrochemical evaluation was carried out in three-electrode
systems namely, reference electrode (calomel), auxiliary (Pt), and
working electrode (MS) in a CH1660D electrochemical workstation. Dif-
ferent concentrations of the imidazole derivatives were prepared and
later evaluated for their electrochemical characteristics after immersing
for 30 min at 30 °C. EIS analysis was carried out in 10.0 kHz to 0.1 Hz fre-
quency range and at an amplitude of 0.005 V. A scan rate of 0.4 mV s−1
was used at −200 to +200 mV potential range in potentiodynamic
ðCRÞa−ðCRÞ
ðCRÞa
E
WL% ¼
p ꢀ 100
where, (CR)a and (CR)p; corrosion rate in the absence and presence of in-
hibitors, S; surface area of the specimen (cm2), ΔW: weight loss, t; im-
mersion time (h).
3

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Fig. 1. Nyquist plots for MS in 0.5 M HCl solution containing different concentrations of (a) IM1 (b) IM2 (c) IM3.
3. Results and discussion
different temperature and various amounts of ammonium acetate as ni-
trogen source. The respective results are summarized in Table 1. After
performing the test reaction at different temperatures (100, 110 and
120 °C) and in a various amounts of ammonium acetate, the highest
conversion was obtained when the reaction mixture was irradiated at
300 W and 110 °C with the concentration of 2 mmol of ammonium
3.1. Synthesis of imidazoles
Initially, to optimize the reaction conditions a model reaction was
performed by the condensation of 4,4′-dimethoxybenzil (1 mmol) and
4-hydroxybenzaldehyde (1 mmol) under solvent-free conditions at
4

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Table 3
Electrochemical impedance parameters for MS in 0.5 M HCl in the absence and presence of different concentrations of IM1, IM2 and IM3.
CPEfilm
CPEdl
Inhibitor
IM1
C (mM)
Yo (μ Ω−1sn)
n1
Rfilm
Yo (μ Ω−1sn)
n2
Rct
Rp
Cdl (F cm−2
)
IE%
0
0.000087
0.8169
0.8000
1.0000
0.7650
0.7734
5.14
0.14
1.87
2.56
5.90
0.21
0.22
0.11
0.23
0.29
0.000016
0.01143
0.001487
0.00003639
0.00002664
1.000
25.1
454
544
617
675
0.19
0.11
0.14
0.32
0.25
30
0.000016
0.01725
0.001412
0.000028
0.000025
0.4
0.6
0.8
1.0
0.0002001
0.0000082
0.00009842
0.00008073
0.8000
0.7886
0.9361
0.9927
454
555
619
681
93
94
95
96
IM2
IM3
0.4
0.6
0.8
1.0
0.00006787
0.00008269
0.00007026
0.00006737
0.9006
0.7309
1.0000
0.7519
275
0.15
0.13
0.35
0.29
0.001411
0.9244
1.0000
0.8136
1.0000
40.1
326
368
434
0.34
0.16
0.23
0.26
315
337
370
444
0.00132
90
91
92
93
10.7
2.40
10.3
0.00002891
0.0001825
0.00002092
0.000028
0.000098
0.000020
0.4
0.6
0.8
1.0
0.0001461
0.0001147
0.00007391
0.00008839
0.7679
0.8000
0.8422
0.7539
7.0
0.0
2.2
6.6
0.10
0.22
0.21
0.32
0.00003857
0.00000000
0.00012460
0.00002914
0.8795
0.8000
0.8047
1.0000
239
280
311
364
0.06
0.09
0.21
0.34
246
280
313
371
0.00002038
0.00004856
0.0000567
0.00002914
88
89
90
92
ðRPÞp−ðRPÞ
ðRPÞp
acetate in solvent-free conditions. Under optimized conditions, the gen-
erality and scope of this approach were assessed with a representative
selection of 4,4′-dimethoxybenzil and various aromatic aldehydes. The
findings are listed in Table 2.
E
RP % ¼
a ꢀ 100
ð5Þ
Inspection of Table 3 reveals that increasing RP values with increas-
ing the inhibitors concentrations and RP values reach 95, 93 and 92%
for IM1, IM2 and IM3, respectively at 1.0 mM concentration suggesting
superior corrosion inhibition protection due to presence of electron-
donating groups in the studied imidazole derivatives. The bodes plots
(Fig. 2a, b & c) explores one-time constant behavior of investigated im-
idazole derivatives. The values of the phase angle for blank are lowest
compare to different concentrations indicating corrosion of MS [36].
The impedance results support that greater inhibition efficiency of IM1
with more electron-donating group (OH) has more absorption capabil-
ity on MS surface compare to IM2 with OCH3 and IM3 with NH2 groups.
Hammett equation generally represents the electron-donating and
electron releasing capability of various functional groups. Hammett
constant (σ) is one of the prominent parameters which describes the
electron-donating and accepting tendency of different substituents.
Hammett constant (σ) value of IM1 and IM2 is +0.12 (σm) and − 0.37
(σp) and for IM3is − 0.16 (σm) and − 0.66 (σp). Positive sign of Ham-
mett constant associated with electron-donating substituents causes in-
creasing corrosion inhibition efficiency. Whereas negative values of
Hammett constant are always associated with electron-withdrawing
substituents [37].
3.2. Electrochemical impedance analysis (EIS)
The Nyquist plots for studied inhibitors (IM1, IM2 & IM3) (Fig. 1a, b &
1c) are obtained by immersing the different concentrations in 0.5 M HCl
for about 30 min. Inspections of the figures revealed that the shape of
the Nyquist plots are semicircles indicating the charge transfer process
is mainly responsible for the corrosion process [29,30]. The impedance
circles are not perfect semicircles. The distorted semicircles may be
due to the surface inhomogeneity and roughness of the MS electrode
[31–33]. Different concentrations of the inhibitors were added and ob-
served the enhancement in the diameter of the semicircle upon increas-
ing the inhibitor concentration. This suggests strong adsorption of the
imidazole derivatives on the MS surface by blocking the active sites.
The semicircle size of the IM1 with electron-donating group OH is
greatest compare to other imidazole derivatives (IM2 with OCH3 and
IM3 with NH2) indicating the presence of more electron-donating
groups in the inhibitors enhances corrosion inhibition by preventing
the rate of corrosion to a greater extent. From the Nyquist plots, we
have selected a suitable equivalent circuit (R(Q(R(QR))) with two
time constant (Fig. 3) and analyzed all the plots. To fit EIS data more ac-
curately the constant phase element (CPE) has been replaced by the ca-
pacitance in the interface, where Rs is the solution resistance; Rf and CPEf
represent the resistance and capacitance of inhibitor film. Rct and CPEdl
represent the charge transfer resistance and double layer capacitance.
The calculated CPEf, CPEdl, Cdl, RP and IE% from the Nyquist plots are
depicted in Table 3. The capacitance in the double layer is replaced
with a constant phase element (CPE) to minimize the deviation caused
due to frequency dispersion [34]. In the process of dissolution of metals
in different acidic media, replacement of Rct by Rp gives better approx-
imation as Rp contains other resistance along with Rct such as film resis-
tance (Rf), i.e., Rp = Rf + Rct [35]. The n value is derived from the Bodes
plots and indicating the deviation from the ideal capacitive behavior.
The broader nature of Bode plots at higher concentrations suggested
an increase in adsorption of inhibitor molecules on the mild steel sur-
face. The ZCPE, double-layer capacitance (Cdl) and η (%) can be calculated
using the following equations:
3.3. Polarization studies
Fig. 4a, b & c depicts the potentiodynamic polarization plots of MS in
the presence and absence of various concentrations of IM1, IM2 and IM3.
Cathodic Tafel slope (βa), current density (icorr) and anodic Tafel slope
(βa) were calculated by the Tafel extrapolation method and the results
are displayed in Table 4. From the figures, a shift of anodic and cathodic
branches of Tafel plots to lower current densities indicates mixed mode
(suppression of anodic metal dissolution and cathodic hydrogen evolu-
tion reactions) of corrosion inhibition. Mixed type of corrosion inhibi-
tion is also confirmed by evaluating the corrosion potential (Ecorr: not
greater than 85 mV) in presence of IM1, IM2 and IM3 and found [38].
From the Table 4, it is also confirmed that the sharp decrease in icorr
values in presence of different concentrations of the imidazole deriva-
tives causing an increase in corrosion inhibition efficiency (η%) reaches
up to 96% for IM1, 94% for IM2 and 93% for IM3 at 1.0 mM. This data sug-
gests the strong corrosion protection efficiency of studied imidazole de-
rivatives. The protonated IM1, IM2 and IM3 reacts with hydrogen ions
and adsorb on the cathodic regions and retard the hydrogen evolution
reaction mediated by H+ ions released by acids. Oxidation of iron gen-
erates Fe2+ at the anode and negative charge caused due to chloride
–n
−1
ZCPE ¼ Yo ðiwÞ
ð3Þ
ð4Þ
ꢀ
ꢁ
1=n
1−n
Cdl
¼
YoRct
5

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Fig. 2. Bodes plots for MS in 0.5 M HCl solution containing different concentrations of (a) IM1 (b) IM2 (c) IM3.
ions from hydrochloric acid would attracts IM1, IM2 and IM3 for adsorp-
tion. Studied imidazole derivatives donate lone pair of electrons and
benzene pi electrons to d orbitals of iron for effective adsorption. The
η% follows the order IM1 > IM2 > M3. The η % at various concentrations
of imidazole derivatives are calculated using the eq. (6),
ꢀ
ꢁ
ꢀ
ꢁ
i0corr − iicorr
ꢀ
ꢁ
Ep% ¼
ꢀ 100
ð6Þ
i0corr
where, (i°corr); current density (μA cm−2) for blank, (iicorr); current den-
sity (μA cm−2) for inhibitors.
Fig. 3. Equivalent circuit diagram.
6

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Fig. 4. Potentiodynamic polarization curves for MS in 0.5 M HCl solution containing different concentrations of (a) IM1 (b) IM2 (c) IM3.
3.4. Weight loss studies
Table 5 depicts the calculated corrosion rate (CR) and inhibition effi-
ciency (η %) values for 4,4′-dimethoxybenzil, 4- hydroxy benzaldehyde,
4- methoxy benzaldehyde, 4- Amino benzaldehyde and all the imidaz-
ole derivatives using weight loss measurements. Inhibition efficiency
of starting compounds are relatively less comparing to other organic
compounds. To achieve higher corrosion inhibition, we have synthe-
sized IM1, IM2 and IM3 and investigated their corrosion inhibition
efficiency. The mass loss studies have been carried out at 303 K for a pe-
riod of 24 h. Results in the table indicate after the addition of IM1, IM2
and IM3 corrosion rate decrease gradually indicating greater η % of in-
vestigated inhibitors. This could be attributed to the presence of π-
electrons in the benzene ring as well as lone pair of electrons on the ni-
trogen atoms of the imidazole derivative which serve as a medium of
adsorption [39].
7

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Fig. 5. Langmuir adsorption isotherm on MS in 0.5 M HCl at different temperatures (a) IM1 (b) IM2 (c) IM3.
3.5. Adsorption studies
isotherms the Langmuir isotherm model was best fitted with very
good correlation coefficients (Very close to 1). Various adsorption ther-
modynamic parameters are calculated by fitting surface coverage values
with functions of inhibitor concentrations. The best fit with a good cor-
relation coefficient was showed by the Langmuir adsorption isotherm
model compare to other isotherms. According to Langmuir adsorption
To establish the interaction between MS surface and IM1, IM2 and
IM3, various adsorption isotherm models were computed. These ad-
sorption models include Langmuir, El -Awady, Frumkin, Temkin,
Freundlich, and Flory -Huggins adsorption isotherms. Among various
8

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Fig. 6. Plot of lnKads versus 1/T.
isotherm, θ is related to the C and Kads (equilibrium constant of adsorp-
tion), using eq. (7), and Kads and Gibbs free energy are related using
Eq. (8)
3.6. QC calculations
In order to understand the geometrical confinement of the imidazole
derivatives, Gaussian 09 package with DFT calculations using B3LYP
functional with 6–311 + G (d,p) level basis set for all atoms [44–46].
The optimized structures, highest occupied molecular orbitals
(HOMO) and lowest unoccupied molecular orbitals (LUMO), electro-
static potential map of neutral and protonated forms of IM1, IM2 and
IM3 were displayed in Fig. 7 and Fig. 8. All the calculated quantum
chemical parameters such as EHOMO, ELUMO, electronegativity (χ), dipole
moment (μ), global hardness (η), energy gap (ΔE), global softness (s),
and electrophilicity index (ω) of the IM1, IM2 and IM3 and their proton-
ated forms are shown in Table 7. Inspection of Fig. 7 revealed that
HOMO density of all the studied imidazole derivatives was located on
both imidazole and bis-methoxy benzene moiety indicating the major
portion of the investigated imidazole derivatives were involved for elec-
tron donation [47], means the studied imidazole derivatives interact
with both the cathodic and anodic sites on the metal surface through al-
most all parts of the inhibitors. Whereas LUMO is located on imidazole
moiety and part of the bis methoxy benzene moiety. The LUMO and
HOMO energy associated with electron-accepting and electron-
donating capacity of the organic inhibitor molecules [48]. The reported
values in Table 7 disclose that the higher HOMO value of IM1 compares
to IM2 and IM3 suggesting greater inhibition efficiency of IM1. The en-
ergy gap gives an idea in understanding the reactivity of the inhibitors.
The lower the value of ΔE exhibits more reactivity of the inhibitor mol-
ecules and exerts greater inhibiting action [49]. The order of the ΔE
values is IM1 < IM2 < IM3. This order indicated that IM1 is the best inhib-
itor compare to other imidazole derivatives and represents a very good
correlation with the experimental results.
The electrode surface characteristics are greatly affected by the ad-
sorption of inhibitor molecules on the surface of MS because of its dipole
moment (μ). The dipole moment indicates the mechanism of inhibition
of inhibitors [50]. The inhibitors with higher μ undergo greater polariza-
tion compare to inhibitors with lesser μ [51]. Therefore, the larger μ
value of IM1 (3.56) compares to IM2 and IM3 suggests higher corrosion
inhibition performance of IM1. Chemical hardness (ƞ) is also an impor-
tant parameter used to predict corrosion inhibition efficiency with the
experimental results. The chemical hardness and inhibition efficiency
are inversely related [52]. According to Koopman's definition another
parameter global softness is the inverse of global hardness. Generally,
the most preferred interaction is between lowered hardness and higher
softness. The hard base and soft acid theory is the basis to consider iron
as soft acid and always shows a tendency to react with soft base. The
C
θ
1
Kads
¼
þ c
ð7Þ
ð8Þ
ꢂ
ꢃ
1
55:5
−ΔGads
RT
Kads
¼
exp
where C is inhibitors concentration, Kads is adsorption equilibrium con-
stant, θ is the surface coverage, T is absolute temperature, R is the uni-
versal gas constant, and 55.5 is the molar concentration of water. The
Langmuir plots for IM1, IM2 and IM3 are presented in (Fig. 5a, b & 5c).
The correlation coefficient values are very close to 1 indicating strong
agreement with the Langmuir adsorption isotherm model. The calcu-
lated thermodynamic adsorption parameters are given in Table 6. The
obtained values reveal that the Kads values follow the order
IM1 > IM2 > IM3 supporting strong adsorption and greater inhibition ef-
ficiency of IM1 compare to other imidazole derivatives. The greater ad-
sorption of the studied imidazole derivatives is may due to interaction
of nitrogen atoms of the imidazole, dimethoxy groups and pi electrons
of the inhibitor and MS surface. On increasing temperature, the values
of Kads decreased, which explains the increase in solution entropy leads
to desorption of inhibitor molecules [40]. The larger values of Kads point
out strong adsorption of IM1, IM2 and IM3 on the surface of MS. The neg-
ative sign of ΔGads (Table 6) reflects in the spontaneity of the adsorption
process. The calculated ΔGads values of IM1, IM2 and IM3 are (−33 to 36
KJ mol−1) once again representing the mixed type of adsorption i.e. in-
volving both physisorption and chemisorption [41]. The enthalpy and
entropy of adsorption (ΔHads and ΔSads) are calculated using eq. (9):
1
55:5
ΔHads ΔSads
lnKads ¼ ln
−
þ
ð9Þ
RT
R
The evaluated values of ΔHads and ΔSads are given in Fig. 6. The neg-
ative values of ΔHads (Table 6) indicate the exothermic nature of the ad-
sorption on the MS surface, further, the positive values of ΔSads indicate
an increase in solvent entropy during adsorption [42]. The increase of
disorders on MS surface is because of the elimination of a large number
of water for the adsorption of one inhibitor molecules [43].
9

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Fig. 7. The optimized structures, HOMOs, LUMOs and electrostatic potential structures of imidazole derivatives.
reported results in Table 7 suggested that IM2 (2.02) and IM2 (2.01)
have higher hardness values compare to IM1 (1.9) supporting greater
inhibition efficiency of IM1. Fig. 7 presents Mulliken charge population
for IM1, IM2 and IM3,C1, O2, C3, C4, C5, C7, C10, N11, N13, C15, C17,
O18, C20, C22, C23, O25, C26 and C28 (IM1), C1, O2, C3, C4, C5, C7,
C10, N11, N13, C15, C16, C17, O18, C19, C21, C23, C24, C25, O26, C27,
C29 (IM2) and C1, O2, C3, C4, C5, C7, C10, N11, N13, C15, N18, C20,
C22, C23, O25, O26, and C28 (IM3) are having excess negative charges.
The higher corrosion inhibition efficiency of all the studied imidazole
derivatives is may be due to the presence of different hetero atoms
such as oxygen and nitrogen atoms. After protonation of nitrogen
atom of imidazole moiety acquires positive charge and adsorbed on
the MS surface (Fe2+) combined with chlorine atom results the forma-
tion of protective complex. This protective layer formation retard corro-
sion of MS to a greater extent [53].
3.7. Surface morphology studies
3.7.1. XPS analysis
Further, to evaluate the composition of film adsorbed on the surface
of MS, XPS analysis has been conducted in 0.5 M Hydrochloric acid solu-
tion for IM1 Inhibitor. The C 1 s spectrum is given in Fig. 9a and it con-
sists of three characteristic peaks of carbon. The peak at 284.5 eV is
the most intense that could be accredited to the presence of C–C, C–H
and C_C in IM1. The N 1 s spectrum in Fig. 9b exhibit two distinct
peaks. The peak at 399.5 eV is attributed to the unprotonated C–N and
C_N of imidazole rings present in IM1 Inhibitor. Another peak posi-
tioned at 400.4 eV is due to the co-ordination of N atoms of IM1 with
the surface of MS and probably leads to the formation of N\\Fe. The
Fe 2p spectrum given in Fig. 9c exhibit a typical two peaks with ghost
structure at 711.6 and 725.1 eV corresponding to Fe 2p3/2 and2p1/2
,
10

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Fig. 8. The optimized structures, HOMOs, LUMOs and electrostatic potential structures of protonated imidazole derivatives.
respectively. The deconvolution of Fe 2p3/2 consists of four major peaks.
The first peak observed at a binding energy of 710.89 eV is ascribed to
Fe2O3 of N–Fe and a peak at 712.3 eV could be assigned to FeOOH. The
other peaks at 714 and 718.75 eV are attributed to the peak of surface
and satellite of Fe (III), respectively. The enhanced corrosion inhibition
efficiency of IM1 on MS in 0.5 M HCl is due to the decrease in the diffu-
sion of ions because of generation of the Fe2O3 and FeOOH insoluble
layer. Two main peaks are observed for O 1 s (Fig. 9d), first one is at
529.95 eV attributed to oxygen atoms of Fe2O3 (detected in Fe 2p spec-
trum). The other intense peak at 531.8 eV is probably due to OH ions of
FeOOH.
3.7.2. XRD analysis
Surface analysis of the MS is further evaluated using XRD studies to
understand the crystalline nature of the layer adsorbed on it. To fur-
ther know the crystalline nature of the layer adsorbed on the surface
of MS, XRD analysis has been carried out. The surface of the MS in
0.5 M HCl in presence and absence of inhibitor was scratched and re-
corded the XRD. Fig. 10a exhibits characteristic peaks at 2θ = 24.140,
33.130, 35.610, 40.870, 49.680, 54.20 and 64.010 are attributed to the
scattering from (012), (104), (110), (113), (024), (116), (214) and
(300), planes respectively (JCPDS card No. 33–0664) assigned to hex-
agonal type α-Fe2O3. Fig. 10b shows the XRD of scratched samples of
11

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Fig. 9. XPS spectra of the MS surface after 24 h immersion in 0.5 M HCl solution uninhibited and inhibited with 0.5 mM IM1.
MS in presence of inhibitor IM1, clearly indicated non-crystallinity
with low intensity indicated amorphous nature of the protective
oxide layer.
3.7.3. Surface studies
MS surface analysis was further examined using scanning electron
microscopic technique to understand the morphology of the MS in
0.5 M HCl in the absence and presence of IM1, IM2 and IM3for 24 h of im-
mersion. Damage on the MS surface has been observed in Fig. 11a due to
the dissolution of the metal in the uninhibited solution. Upon addition
of the imidazole derivatives as an inhibitor to the corrosive solution,
no evidence of the cracks and pits on the surface was observed in the
Figs. 11(b)-11(d). These SEM images suggest a uniform surface of the
MS due to the homogenous adsorption of inhibitors on its surface and
indicate studied IM1, IM22 and IM3 derivatives as inhibitors exhibit
great affinity to adhere on MS surface.
4. Conclusions
Three imidazole derivatives have been evaluated for their corrosion
inhibition efficiency on MS in 0.5 M HCl medium. The results suggest, in-
hibition efficiencies of all the inhibitors increase with the increase in its
concentration, IM1 with OH functional group exhibited maximum inhi-
bition efficiency up to 96% compared to other imidazoles. Inhibition
Fig. 10. XRD patterns of MS scratched sample after immersion in 0.5 M HCl and MS
scratched sample after immersion in 0.5 M HCl in presence of IM1.
12

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Fig. 11. SEM images of MS in 0.5 M HCl after 24 h immersion at (a) without inhibitor (blank) (b) with 1.0 mM IM1 (c) with 1.0 mM IM2 (d) with 1.0 mM IM3.
Table 4
Potentiodynamic polarization parameters for MS in 0.5 M HCl in the absence and presence of different concentrations of IM1, IM2 and IM3.
Inhibitor
C (mM)
Ecorr (mV)
Icorr (μA cm−2
)
β
a (mA dec−1
)
−βc (mA dec−1
)
η (%)
0
−0.588
−0.549
−0.556
−0.557
−0.528
0.31
0.52
0.46
0.23
0.44
766
53
46
40
31
0.20
0.21
0.20
0.19
0.20
5.34
8.70
6.97
7.30
8.42
0.25
0.29
0.23
0.34
0.29
7.15
13.4
11.8
11.9
13.9
0.16
0.19
0.24
0.21
0.20
IM1
0.4
0.6
0.8
1.0
93.0
93.9
94.7
95.9
IM2
IM3
0.4
0.6
0.8
1.0
−0.565
−0.568
−0.539
−0.545
0.28
0.30
0.24
0.26
69
62
51
42
0.32
0.31
0.34
0.26
4.45
5.34
11.2
10.74
0.15
0.19
0.11
11.1
11.6
14.3
14.8
0.27
0.21
0.15
0.23
90.9
91.8
93.3
94.5
0.34
0.4
0.6
0.8
1.0
−0.569
−0.568
−0.550
−0.524
0.36
0.31
0.30
0.21
78
70
54
49
0.19
0.23
0.22
0.21
5.53
6.15
8.44
11.84
0.32
0.17
0.22
12.6
10.1
13.9
10.29
0.16
0.15
0.21
89.8
90.8
92.9
93.6
0.26
0.25
Author statement
efficiencies obtained by different electrochemical and weight loss
methods are in good agreement with each other, inhibition efficiencies
trend follows the order IM1 > IM2 > IM3. The mechanism of adsorption
of all the imidazoles follows the Langmuir isotherm model. A mixed
type of corrosion inhibition activity was indicated by polarization stud-
ies. RP values in EIS measurements increase with increasing inhibitor
concentrations. SEM, XRD and XPS analysis was used to investigate
the protective layer formed on the MS surface. Finally, experimental re-
sults are well correlated theoretically by using the DFT method.
On behalf of all the coauthors am declaring that this manuscript is
original, has not been published before and is not currently being con-
sidered for publication elsewhere. I confirm that the manuscript has
been read and approved by all named authors and that there are no
other persons who satisfied the criteria for authorship but are not listed.
I further confirm that the order of authors listed in the manuscript has
been approved by all of us.
13

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
Declaration of Competing Interest
This manuscript has not been submitted to, nor is under review at,
another journal or other publishing venue.
All authors have participated in (a) conception and design, or analy-
sis and interpretation of the data; (b) drafting the article or revising it
critically for important intellectual content; and (c) approval of the final
version.
The authors have no affiliation with any organization with a direct or
indirect financial interest in the subject matter discussed in the
manuscript
References
[1] E. Kusmierek, E. Chrzescijanska, Atmospheric corrosion of metals in industrial city
environment, Data Brief 3 (2015) 149–154.
Table 5
[2] D. Balgude, A. Sabnis, Sol–gel derived hybrid coatings as an environment friendly
surface treatment for corrosion protection of metals and their alloys, J. Sol-Gel Sci.
Tech. 64 (2012) 124–134.
Weight loss data of MS in 0.5 M HCl for various concentrations of IM1, IM2 and IM3 at
303 K.
Inhibitor
Concentration
(mM)
Corrosion rate
(mg cm−2 h−1
η
(%)
[3] A.A. Nazeer, M. Madkour, Potential use of smart coatings for corrosion protection of
metals and alloys: a review, J. Mol. Liq. 253 (2018) 11–22.
)
[4] S. Pareek, D. Jain, S. Hussain, A. Biswas, R. Shrivastava, S.K. Parida, H.K. Kisan, H. Lgaz,
I.-M. Chung, D. Behera, A new insight into corrosion inhibition mechanism of copper
in aerated 3.5 wt.% NaCl solution by eco-friendly Imidazopyrimidine dye: experi-
mental and theoretical approach, Chem. Eng. J. 358 (2019) 725–742.
[5] C.B. Pradeep Kumar, M.K. Prashanth, K.N. Mohana, M.B. Jagadeesha, M.S. Raghu, N.K.
Lokanath, K. Yogesh Kumar, Protection of mild steel corrosion by three new
Quinazoline derivatives: experimental and DFT studies, Surf. Interfaces 18 (2020),
100446, .
[6] C.B. Pradeep Kumar, K.N. Mohana, M.S. Raghu, M.B. Jagadeesha, M.K. Prashanth, N.K.
Lokanath, Mahesha, “fluorine substituted thiomethyl pyrimidine derivatives as effi-
cient inhibitors for mild steel corrosion in hydrochloric acid solution: thermody-
namic, electrochemical and DFT studies”, J. Mol. Liq. 113311 (2020).
[7] C.B. Pradeep Kumar, K.N. Mohana, Corrosion inhibition efficiency and adsorption
characteristics of some Schiff bases at mild steel/hydrochloric acid interface, J.
Taiwan Inst. Chem. Eng. 45 (2014) 1031–1042.
Blank
0.4283
0.1462
0.2955
0.3055
1.10
1.22
1.76
0.83
4,4′-dimethoxybenzil
4- hydroxy benzaldehyde
4- methoxy
benzaldehyde
4- Amino benzaldehyde
IM1
1.0
1.0
1.0
65
31
28
1.0
0.4
0.6
0.8
1.0
0.4
0.6
0.8
1.0
0.4
0.6
0.8
1.0
0.3088
0.0467
0.0805
0.0322
0.0372
0.0255
0.0459
0.0343
0.0434
0.0546
0.1192
0.0752
0.1512
0.91
0.98
1.10
0.94
1.23
0.83
0.86
1.32
0.97
0.88
0.76
0.72
0.92
27
93
94
95
96
90
92
92
94
88
89
90
92
IM2
IM3
[8] V. Kalia, P. Kumar, S. Kumar, P. Pahuja, G. Jhaa, S. Lata, H. Dahiya, Synthesized
oxadiazole derivatives as benign agents for controlling mild steel dissolution: ex-
perimental and theoretical approach, J. Mol. Liq. 313 (2020) 113601.
[9] T. Nesakumar, J.I. Edison, R. Atchudan, A. Pugazhendhi, Y. Rok Lee, M.G. Sethuraman,
Corrosion inhibition performance of spermidine on mild steel in acid media, J. Mol.
Liq. 264 (2018) 483–489.
[10] J.O. Mendes, E.C. da Silva, A.B. Rocha, On the nature of inhibition performance of im-
idazole on iron surface, Corros. Sci. 57 (2012) 254–259.
[11] A. Popova, M. Christov, S. Raicheva, E. Sokolova, Adsorption and inhibitive properties
of benzimidazole derivatives in acid mild steel corrosion, Corros. Sci. 46 (2004)
1333–1350.
[12] S. Varvara, L.M. Muresan, K. Rahmouni, H. Takenouti, Evaluation of some non-toxic
thiadiazole derivatives as bronze corrosion inhibitors in aqueous solution, Corros.
Sci. 50 (2008) 2596–2604.
[13] M. Ouakki, M. Rbaa, M. Galai, B. Lakhrissi, E.H. Rifi, M. Cherkaoui, Experimental and
quantum chemical investigation of imidazole derivatives as corrosion inhibitors on
mild steel in 1.0 m hydrochloric acid, J. Bio. Tribo Corros. 4 (2018) 35.
[14] V. Srivastava, M. Salman, D.S. Chauhan, S. Abdelazeim, M.A. Quraishi, (E)-2-styryl-
1H-benzo[d]imidazole as novel green corrosion inhibitor for carbon steel: experi-
mental and computational approach, J. Mol. Liq. 324 (2020), 115010, .
[15] M. Ouakki, M. Galai, M. Rbaa, Ashraf S. Abousalem, B. Lakhrissi, M. EbnTouhami, M.
Cherkaoui, Electrochemical, thermodynamic and theoretical studies of some imid-
azole derivatives compounds as acid corrosion inhibitors for mild steel, J. Mol. Liq.
319 (2020), 114063, .
[16] M. Talari, S.M. Nezhad, S.J. Alavi, M. Mohtashamipour, A. Davoodi, S. Hosseinpour,
Experimental and computational chemistry studies of two imidazole-based com-
pounds as corrosion inhibitors for mild steel in HCl solution, J. Mol. Liq. 286
(2019) 110915.
[17] M. Ouakki, M. Rbaa, M.B. Lakhrissi Galai, E.H. Rifi, M. Cherkaoui, Experimental and
quantum chemical investigation of imidazole derivatives as corrosion inhibitors
on mild steel in 1.0 m hydrochloric acid, J. Bio. Tribo Corros. 4 (2018) 35.
Table 6
Thermodynamic parameters of adsorption for MS in 0.5 M HCl at different temperatures
from Langmuir adsorption isotherm.
Inhibitor Temperature
(K)
Kads
ΔGads
ΔHads
ΔSads
(L mol−1
)
(kJ mol−1
)
(kJ mol−1
)
(J mol−1 K−1
)
IM1
IM2
IM3
303
313
323
333
26,010
23,420
21,611
20,121
−33.9
−34.5
−35.5
−36.1
−8.1
−8.6
−11.1
82
83
71
303
313
323
333
22,121
20,100
17,221
15,844
−33.2
−34.5
−35.3
−36.0
303
313
323
333
21,312
19,721
17,644
13,492
−33.6
−34.4
−35.1
−36.8
Table 7
Quantum chemical parameters for neutral and protonated IM1, IM2 and IM3.
Neutral
Protonated
Molecular Properties
EHOMO (eV)
IM1
IM2
IM3
IM1
IM2
IM3
−4.9111
−0.9334
3.9778
4.9111
0.9334
1.9889
0.9944
−2.9223
2.9223
2.1468
3.56
−5.1963
−1.1562
4.0401
5.1963
1.1562
2.0201
1.0100
−3.1763
3.1763
2.4971
3.25
−5.1400
−1.1162
4.0238
5.1400
1.1162
2.0119
1.0059
−3.1281
3.1281
2.4318
3.21
−2.0341
−0.7796
1.3785
2.3211
0.7796
0.6893
0.3446
1.5504
−1.5504
1.5593
6.22
−2.3021
−0.7687
1.5334
2.3021
0.7687
0.7667
0.3833
1.5354
−1.5354
1.5375
5.83
−2.3211
−0.6555
1.5415
2.0341
0.6555
0.7708
0.3854
1.3448
−1.3448
1.3119
2.98
ELUMO (eV)
EHOMO - ELUMO gap (eV)
Ionization Potential (I) (eV)
Electron affinity (A) (eV)
Global hardness (η)
Global Softness (S)
Chemical potential (μ)
Electro negativity (χ)
Electrophilicity index (ω)
Dipole moment (μ)
14

M.K. Prashanth, C.B.P. Kumar, B.S. Prathibha et al.
Journal of Molecular Liquids 329 (2021) 115587
[18] M. Ouakki, M. Galai Rbaa, M. Ashraf, S. Abousalem, B. Lakhrissi, E.H. Rifi, M.
Cherkaoui, Investigation of imidazole derivatives as corrosion inhibitors for mild
steel in sulfuric acidic environment: experimental and theoretical studies, Ionics
26 (2020) 5251.
[36] A. Dehghani, G. Bahlakeh, B. Ramezanzadeh, M. Ramezanzadeh, Detailed macro−/
micro-scale exploration of the excellent active corrosion inhibition of a novel envi-
ronmentally friendly green inhibitor for carbon steel in acidic environments, J.
Taiwan Inst. Chem. Eng. 100 (2019) 239–261.
[37] C. Verma, E.E. Ebenso, M.A. Quraishi, Molecular structural aspects of organic corro-
sion inhibitors: influence of –CN and –NO2 substituents on designing of potential
corrosion inhibitors for aqueous media, J. Mol. Liq. 316 (2020) 113874.
[38] C.B. Pradeep Kumar, K.N. Mohana, Phytochemical screening and corrosion inhibitive
behavior of Pterolobium hexapetalum and Celosia argentea plant extracts on mild
steel in industrial water medium, Egypt. J. Pet. 23 (2014) 201–211.
[39] A. Singh, K.R. Ansari, D.S. Chauhan, M.A. Quraishi, H. Lgaz, Comprehensive investiga-
tion of steel corrosion inhibition at macro/micro level by ecofriendly green corrosion
inhibitor in 15% HCl medium, J. Colloid Interface Sci. 560 (2020) 225–236.
[40] L. Jiang, Y. Qiang, Z. Lei, J. Wang, Z. Qin, B. Xiang, Excellent corrosion inhibition per-
formance of novel quinoline derivatives on mild steel in HCl media: experimental
and computational investigations, J. Mol. Liq. 255 (2018) 53–63.
[41] R. Solmaz, G. Kardas, B. Yazıcı, M. Erbil, Adsorption and corrosion inhibitive proper-
ties of 2-amino-5-mercapto-1,3,4-thiadiazole on mild steel in hydrochloric acid
media, Colloids Surfaces A 312 (2008) 7–17.
[42] R.S.A. Hameed, Aminolysis of polyethylene terephthalate waste as corrosion inhibi-
tor for carbon steel in HCl corrosive medium, Adv. Appl. Sci. Res. 2 (2011) 483–499.
[43] M. Bouklah, B. Hammouti, M. Lagrenee, F. Bentiss, Thermodynamic properties of 2,5-
bis(4-methoxyphenyl)-1,3,4-oxadiazole as a corrosion inhibitor for mild steel in
normal sulfuric acid medium, Corros. Sci. 48 (2006) 2831–2842.
[44] C. Lee, W. Yang, R.G. Parr, Development of the Colle-Salvetti correlation-energy for-
mula into a functional of the electron density, Phys. Rev. B 37 (1988) 785–789.
[45] A.D. Becke, Density-functional thermochemistry. I. the effect of the exchange-only
gradient correction, J. Chem. Phys. 96 (1992) 2155–2160.
[46] P.C. Hariharan, J.A. Pople, The influence of polarization functions on molecular or-
bital hydrogenation energies, Theor. Chem. Accounts 28 (1973) 213–222.
[47] S.K. Saha, A. Dutta, P. Ghosh, D. Sukul, P. Banerjee, Novel Schiff-base molecules as ef-
ficient corrosion inhibitors for mild steel surface in 1 M HCl medium: experimental
and theoretical approach, Phys. Chem. 18 (2016) 17898–17911.
[48] S. Xia, M. Qiu, L. Yu, F. Liu, H. Zhao, Molecular dynamics and density functional the-
ory study on relationship between structure of imidazoline derivatives and inhibi-
tion performance, Corros. Sci. 50 (2008) 2021–2029.
[49] M. Ozcan, I. Dehri, M. Erbil, Organic Sulphur-containing compounds as corrosion in-
hibitors for mild steel in acidic media: correlation between inhibition efficiency and
chemical structure, Appl. Surf. Sci. 236 (2004) 155–164.
[19] N.S. Patel, S. Jauhari, G.N. Mehta, The inhibition of mild steel corrosion in 1 n hcl by
imidazole derivatives, Acta Chim. Slov. 57 (2010) 497.
[20] U. Eduok, O. Faye, J. Szpunar, Corrosion inhibition of X70 sheets by a film-forming
imidazole derivative at acidic pH, RSC Adv. 6 (2016), 108777, .
[21] T. Yan, S. Zhang, L. Feng, Y. Qiang, L. Lu, D. Fu, Y. Wen, J. Chen, W. Li, B. Tan, Investi-
gation of imidazole derivatives as corrosion inhibitors of copper in sulfuric acid:
combination of experimental and theoretical researches, J. Taiwan Inst. Chem. Eng.
106 (2020) 118.
[22] T. Yan, S. Zhang, L. Feng, Y. Qiang, L. Lu, D. Fu, Y. Wen, J. Chen, W. Li, B. Tan, Investi-
gation of imidazole derivatives as corrosion inhibitors of copper in sulfuric acid:
combination of experimental and theoretical researches, J. Taiwan Inst. Chem. Eng.
106 (2019) 118–129.
[23] U. Eduok, O. Faye, J. Szpunar, Corrosion inhibition of X70 sheets by a film-forming
imidazole derivative at acidic pH, RSC Adv. 6 (2016) 108777.
[24] A. Shaabani, A.J. Rahmati, Silica sulfuric acid as an efficient and recoverable catalyst
for the synthesis of trisubstituted imidazoles, J. Mol. Catal. A Chem. 249 (2006)
246–248.
[25] B. Karami, K. Eskandari, A. Ghasemi, Facile and rapid synthesis of some novel
polysubstituted imidazoles by employing magnetic Fe3O4 nanoparticles as a high
efficient catalyst, Croat. Chem. Acta 36 (2012) 601.
[26] A. Teimouri, A.N. Chermahini, An efficient and one-pot synthesis of 2,4,5-trisubsti-
tuted and 1,2,4,5-tetrasubstituted imidazoles catalyzed via solid acid nano-
catalyst, J. Mol. Catal. A Chem. 46 (2011) 39–45.
[27] A.R. Khosropour, Ultrasound-promoted greener synthesis of 2,4,5-trisubstituted im-
idazoles catalyzed by Zr(acac)4 under ambient conditions, Ultrason. Sonochem. 15
(2008) 659–664.
[28] M.S. Raghu, C.B. Pradeep Kumar, K.N.N. Prasad, S. Chandrasekhar, K. Yogesh Kumar,
M.K. Prashanth, B. Veeresh, MoS2-CA4 catalyzed synthesis and molecular docking
study of 2,4,5-trisubstituted imidazoles as potent inhibitors of Mycobacterium tuber-
culosis, ACS Comb. Sci. 22 (2020) 509–518.
[29] C. Gabrielli, Identification of Electrochemical Processes by Frequency Response
Analysis: Technical Report Number 004/83, Schlumberger Instruments, 1984.
[30] S.F. Mertens, C. Xhoffer, B.C. De Cooman, E. Temmerman, Short-term deterioration
of polymer-coated 55% Al-Zn — part 1: behavior of thin polymer films, Corrosion.
53 (1997) 381–388.
[50] G. Gece, The use of quantum chemical methods in corrosion inhibitor studies,
[31] G. Trabanelli, C. Monticelli, V. Grassi, A. Frignani, Electrochemical study on inhibitors
of rebar corrosion in carbonated concrete, Cem. Concr. Res. 35 (2005) 1804–1813.
[32] S.K. Shukla, M.A. Quraishi, Cefotaxime sodium: a new and efficient corrosion inhib-
itor for mild steel in hydrochloric acid solution, Corros. Sci. 51 (2009) 1007–1011.
[33] W.R. Fawcett, Z. Kováčová, A.J. Motheo, C.A. Foss, Application of the ac admittance
technique to double-layer studies on polycrystalline gold electrodes, J. Ectroanal.
Chem. 326 (1992) 91–103.
[34] C. Verma, A.A. Sorour, E.E. Ebenso, M.A. Quraishi, Inhibition performance of three
naphthyridine derivatives for mild steel corrosion in 1M HCl: computation and ex-
perimental analyses, Results Phys. 10 (2018) 504–511.
Corros. Sci. 50 (2008) 2981–2992.
[51] A. Mishra, C. Verma, H. Lgaz, V. Srivastava, M.A. Quraishi, E.E. Ebenso, Synthesis,
characterization, and corrosion inhibition studies of N-phenyl-benzamides on the
acidic corrosion of mild steel: experimental and computational studies, J. Mol. Liq.
251 (2018) 317–332.
[52] L.O. Olasunkanmi, M.F. Sebona, E.E. Ebenso, Influence of 6-phenyl-3(2H)-
pyridazinone and 3-chloro-6-phenylpyrazine on mild steel corrosion in 0.5 M HCl
medium: experimental and theoretical studies, J. Mol. Struct. 1149 (2017) 549–559.
[53] E.A. Yaqo, R.A. Anaee, M.H. Abdul Majeed, I. Hameed R. Tomi, M. Mohammed
Kadhim, Potentiodynamic polarization, surface analyses and computational studies
of a 1,3,4-thiadiazole compound as a corrosion inhibitor for Iraqi kerosene tanks, J.
Mol. Struct. 1202 (2020) 127356.
[35] A. Doner, E.A. Sahin, G. Kardas, O. Serindag, Investigation of corrosion inhibition ef-
fect of 3-[(2-hydroxy-benzylidene)-amino]-2-thioxo-thiazolidin-4-one on corro-
sion of mild steel in the acidic medium, Corros. Sci. 66 (2013) 278–284.
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