Synthesis and assessment of new cationic gemini surfactants as inhibitors for carbon steel corrosion in oilfield water

Article abstract of DOI:10.1039/c7ra07176k

Three gemini surfactants were synthesized having the same length of terminal chain but differing in the spacer chain length and they were evaluated as corrosion inhibitors for carbon steel in oilfield water using weight loss, EIS, potentiodynamic polarization and open-circuit potential measurements. These measurements revealed that the synthesized materials have served as effective mixed-type corrosion inhibitors. Their adsorption on a carbon steel surface was well described by means of the Langmuir adsorption isotherm. The activation parameters for the dissolution of carbon steel in solutions of oilfield water in the absence and presence of these inhibitors were calculated. The effect of immersion time on the stability and durability of protective films adsorbed on a carbon steel surface was studied using weight loss method. Ex situ inspection, i.e. post-exposure analysis, for the treated carbon steel surface has been performed using SEM, EDX and FT-IR tools.

Full text of DOI:10.1039/c7ra07176k

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PAPER
Synthesis and assessment of new cationic gemini
surfactants as inhibitors for carbon steel corrosion
in oilfield water†
Cite this: RSC Adv., 2017, 7, 47335
F. El-Taib Heakal, *a M. A. Deyab,
b
b
b
b
M. M. Osman, M. I. Nessim and A. E. Elkholy
Three gemini surfactants were synthesized having the same length of terminal chain but differing in the
spacer chain length and they were evaluated as corrosion inhibitors for carbon steel in oilfield water
using weight loss, EIS, potentiodynamic polarization and open-circuit potential measurements. These
measurements revealed that the synthesized materials have served as effective mixed-type corrosion
inhibitors. Their adsorption on a carbon steel surface was well described by means of the Langmuir
adsorption isotherm. The activation parameters for the dissolution of carbon steel in solutions of oilfield
water in the absence and presence of these inhibitors were calculated. The effect of immersion time on
the stability and durability of protective films adsorbed on a carbon steel surface was studied using
weight loss method. Ex situ inspection, i.e. post-exposure analysis, for the treated carbon steel surface
has been performed using SEM, EDX and FT-IR tools.
Received 28th June 2017
Accepted 30th September 2017
DOI: 10.1039/c7ra07176k
rsc.li/rsc-advances
Among the methods followed for protecting metals against
their corrosion is using corrosion inhibitors. It is the most
1
. Introduction
Carbon steel (C-steel) is the main engineering material used in suitable procedure because of its high efficiency, economic
5
constructing pipelines for transferring water, chemicals and advantages, and wide applicability in various elds. A corro-
petroleum products in addition to vessels used in oil and gas sion inhibitor is any material that can reduce the corrosion rate
6
production systems. This broad usage of carbon steel is due to its of a metal via displacing water molecules from the vicinity of
1,2
excellent mechanical properties and cheapness. Unfortunately, the metallic surface then its molecules can interact with the
7
carbon steel-based materials are vulnerable to corrosion by their anodic and/or cathodic sites by adsorption. These materials
neighboring environment. Among the corrosive media doing can be classied according to their chemical nature into three
violence to C-steel is oileld water which naturally exists in gas genres: (i) inorganic inhibitors, (ii) organic inhibitors, and (iii)
8
and oil reservoirs. It contains huge amounts of dissolved salts (e.g. mixed-compound inhibitors. Nevertheless, most commonly
chloride and sulfate ions) and dissolved corrosive gases (e.g. CO
2
used inhibitors are organic compounds especially those con-
3
9
and H
2
S) as well. In petroleum oilelds, the disposal of oileld taining hetero atoms (O, N and/or S) and/or those containing
10
water separated from crude oil represents a nuisance for workers multiple bonds or aromatic rings (p-systems). Inhibition
in the petroleum industry because it is highly saline and polluted process can be performed by electrons transfer between the
by oil. So, this water is mixed with fresh water and re-injected in inhibitor and the metal surface (vacant d-orbitals) forming
11
the oil wells so as to stimulate the crude oil stuck to rocks in the coordinate covalent bonds between them. Furthermore,
oil reservoir to be recovered with the advantage of increasing the adsorption can be due to electrostatic interaction between the
12
oil productivity on one hand and the disposal of oileld water on metal surface and inhibitor molecules. As a result, inhibitor
the other hand in a process called hydraulic fracturing. Before adsorption relies on the surface charge of the metal, i.e., the
injection, some chemicals are added to this uid such as scale adsorption of cations is favored if the net charge is negative
and corrosion inhibitors to prevent scale deposition inside oil while adsorption of anions is favored when the case is
4
11
pipelines and also to prevent their corrosion.
reversed.
Surfactants, or surface active agents, are a general class of
organic chemical compounds of amphiphilic molecules, each
a
Chemistry Department, Faculty of Science, Cairo University, 12613 Giza, Egypt. of them contains a hydrophobic (non-polar) tail and a hydro-
E-mail: fakihaheakal@yahoo.com; feltaibheakal@gmail.com; Fax: +20 35738425;
13
philic (polar) head. Usually, the hydrophilic head (either polar
Tel: +20 1002449048
b
or ionic group) of surfactant molecule attaches to the metal
surface and its tail or hydrophobic moiety extends away from
the interface towards the solution bulk forming an array of
Department of Analysis and Evaluation, Egyptian Petroleum Research Institute, 11727
Cairo, Egypt
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c7ra07176k
hydrophobic tails which leads to
a
change in the
1
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Paper
Table 1 Physical properties of oilfield water
Physical property
Value
111.9255 g l
ꢁ
1
Total dissolved solids
Conductivity
ꢁ1
14.61 mohs cm @ 20.1
ꢂ
C
ꢂ
Resistivity
Salinity
pH
Density
Specic gravity
Hardness
0.0685 ohm m @ 20.1 C
ꢁ1
109.5072 g l
ꢂ
6.85 @ 25 C
Fig. 1 Shape of gemini surfactant molecule.
ꢁ
1
ꢂ
1.0842 g ml @ 15.56 C
1.0853
ꢁ
1
25.0657 g l
electrochemical behavior of metal (increasing the corrosion
14
resistance). Gemini surfactants are a class of surfactants in
which the molecule is composed of two identical molecules of
ordinary surfactant linked together via a linkage called spacer Table 2 Chemical composition of oilfield water
1
5
(
Fig. 1). This spacer may be hydrophilic or hydrophobic, short
16
Concentration
Concentration
or long and rigid or exible. The current study aims to inves-
tigate the corrosion inhibition efficiency of some developed
cationic gemini surfactants for C-steel in oileld water. These
ꢁ
1
ꢁ1
Constituents
Lithium
(mg l
)
Constituents
(mg l
)
0.01
Fluoride
Chloride
Bromide
Nitrate
Hydroxide
Carbonate
Bicarbonate
Sulfate
0.00
surfactants were prepared in the series of a,u-alkanediyl bis(3- Sodium
30 543.00
3402.13
1197.24
8063.85
38.69
0.15
Nil
Nil
66 368.00
209.45
Nil
Nil
Nil
Potassium
dodecylimidazolium-1-yl)dibromide with the same length of
terminal chains but differing in the length of spacer chain (2, 6
and 10 methylene groups).
Magnesium
Calcium
Iron
Copper
Strontium
Barium
244.00
1859.00
2. Materials and experimental
methods
ꢀ
pH value was determined according to ASTM D-1293 using
2.1. Materials
digital pH meter model Mettler Toledo-Seven Go.
Carbon steel samples used in all experiments has the following
elemental composition (in wt%): 0.200 C, 0.350 Mn, 0.024 P,
2
ꢁ
ꢁ
ꢁ
3
ꢀ
Alkaline species (CO
3
, OH , and HCO ) were measured
according to ASTM D-3875 calculations was done using Alka-
linity calculator ver. 2.10 (USGS).
0.003 Si and balance Fe. C-steel electrode and weight loss
coupons were polished before each experiment with several
emery sheets ranging from 400 to 2500 grades, washed with
distilled water and dried using a lter paper.
The test solution used in this study was oileld water free
from oils and greases. It was collected from several Egyptian
oilelds. The physical properties and chemical composition of
oileld water are shown in Tables 1 and 2, respectively. The
components of this medium are known to be highly corrosive to
The corrosion inhibitors used in this study are some cationic
gemini surfactants differing in the length of spacer chain (2, 6
and 10 methylene groups). For simplicity, they are abbreviated
according to their spacer length as GS2, GS6 and GS10,
respectively. The chemicals from which these gemini surfac-
tants are prepared have been purchased from Alfa Aesar Co.
These chemicals are namely, 1H-imidazole (99%), 1-bromodo-
decane (98%), 1,2-dibromoethane (99%), 1,6-dibromohexane
17,18
the oil extraction structures.
(
97%), 1,10-dibromo decane (97%), acetonitrile (HPLC grade)
and KOH (pellets).
Anions and cations of oileld water were determined
according to ASTM D-4327 and 6919, respectively using ion
chromatography. The instrument used was Dionex IC model
ICS 1100 equipped with high capacity columns (AS9 and CS12)
2
.2. Synthesis of gemini surfactants
for anion and cations, respectively. Heavy metals present in The three imidazolium-based gemini surfactants are prepared
oileld water were determined using Flame Atomic Absorption through two steps as follows:
Spectrophotometer model Zenit 700p according to ASTM
2.2.1. Synthesis of 1-dodecyl-1H-imidazole. 1-Dodecy-1H-
D4691. Physical properties of oileld water including density, imidazole represents the monomeric form (the intermediate
specic gravity, pH, etc., were measured according to the compound) of the three gemini surfactants under study. It was
following standard procedures:
prepared by mixing 0.1 mol dodecyl bromide (2.49 g) with
0.1 mol imidazole (6.8 g) and 5.6 g KOH in 50 ml acetonitrile as
ꢀ
TDS was determined according to ASTM D-1888.
Conductivity and resistivity was determined on site using a solvent (Scheme 1). This mixture was continuously stirred at
ꢀ
digital conductivity meter WTW 330I according to ASTM D- room temperature for about three hours. The product (the
1
125.
Density and specic gravity was determined according to precipitate (KBr). The nal product was recrystallized from
ASTM D-1429. acetonitrile by evaporation under vacuum.
monomer dissolved in acetonitrile) was ltered off from the
ꢀ
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Dw
n ¼
(1)
t ꢃ A
n
0
ꢁ n
E
w
% ¼
ꢃ 100
(2)
n
0
ꢁ2
ꢁ1
where n
o
and n are the corrosion rates (mg cm
h
) of carbon
Scheme 1 Synthetic route for 1-dodecyl-1H-imidazole.
steel in oileld water in absence and presence of inhibitors,
respectively. Dw is the weight loss of the specimen in mg. A is
the total surface area of specimens in cm . t is the immersion
2
2.2.2. Synthesis of gemini surfactants. The desired gemini
time in hours.
surfactants (GS2, GS6 and GS10) were synthesized by a coupling
reaction between 1-dodecyl-1H-imidazole (0.2 mol) with 1,2-
dibromoethane, 1,6-dibromohexane and 1,10-dibromodecane
2.4.2. Electrochemical measurements. A three-electrode
glass cell with a capacity of 100 ml was used in all electro-
chemical experiments. A platinum sheet and a saturated
calomel electrode (SCE) have served as counter and reference
electrodes, respectively. The working electrode designed from
(
0.1 mol), respectively in 50 ml acetonitrile (Scheme 2). The
ꢂ
reaction mixture was reuxed for 12 h at 80 C. Produced gemini
surfactants were recrystallized from acetonitrile by evaporation
under vacuum.
2
carbon steel has a xed surface area of 0.285 cm exposed to test
solution. All electrochemical experiments were always carried
out using the electrochemical work station IM6e Zahner-
electrik, Kronach, Germany, provided with Thales soware.
All electrochemical corrosion parameters were calculated using
EC-Lab V10.40 corrosion soware whilst EIS parameters were
calculated using Thales Z1.28 Soware. Before polarization and
impedance experiments, open-circuit potential of the working
electrode is measured with time till reaching a steady state value
2.3. Characterization of the synthesized gemini surfactants
The synthesized gemini surfactants were characterized using
elemental analysis, mass spectrometry, Fourier transform
1
infrared (FT-IR) spectroscopy and H -NMR spectroscopy. Mass
spectrometric analysis was performed using Thermo Scientic
ISQ QD GC-MS system. FT-IR spectroscopic analysis was per-
formed using KBr pellets via Perkin Elmer, model: Spectrum
(E
ss) aer about 30 minutes. EIS experiments were carried out at
E
ss using a single sinusoidal perturbation signal of 10 mV peak
1
One FT-IR spectrometer. H -NMR spectroscopy was carried out
to peak amplitude while the frequency is changed over the
range (100 kHz to 10 MHz).
in CDCl using Varian Gemini-200 MHz system. Thermogravi-
3
metric analysis (TGA) was carried out for the synthesized
surfactants to determine their thermal stability using simulta-
neous TGA-DSC, model: SDT Q600, USA. Critical micelle
concentration (CMC) was measured in oileld water at room
temperature using Du-Nouy tensiometer (KRUSS K6, Type
In case of the electrochemical impedance spectroscopy, the
corrosion inhibition efficiency (E
calculated from the value of the total resistance (R
surface (R + Rct ¼ R + R ) obtained from EIS measure-
¼ R
ments, according to the following equation:
i
%) for all inhibitors was
t
) of the metal
t
f
1
2
20,21
4851). All gures and tables concerning the characterization of
R
t
ꢁ RtðoÞ
the prepared gemini surfactants are included as ESI materials.†
E
i
% ¼
ꢃ 100
(3)
R
t
where Rt(o) and R is the total corrosion resistance of the metal
surface in the absence and presence of inhibitors,
respectively.
t
2
.4. Methodology
2.4.1. Chemical measurements. Carbon steel specimens of
3
dimensions 1 ꢃ 0.9 ꢃ 0.3 cm were prepared, weighed and then
immersed in 50 ml oileld water solutions free and containing
different concentrations of inhibitors for one week (168 h). Aer
that, the specimens are removed from the electrolyte, corrosion
products are removed and the specimens were washed with
distilled water. Then, they are dried using a lter paper and
reweighed using an analytical balance (model: Precisa 205 A,
having a precision of ꢄ0.1 mg). The weight loss method is
The potentiodynamic polarization measurements were
ꢁ1
carried out at a scan rate of 5 mV s starting from ꢁ1 to ꢁ0.4 V
vs. SCE). The inhibition efficiency (E %) was determined using
(
p
20,22
corrosion current density according to eqn (4):
0corr
I
ꢁ Icorr
corr
E
p
% ¼
ꢃ 100
(4)
0
I
0
where I corr and Icorr are the uninhibited and the inhibited
employed to calculate the corrosion rate (n). The values of corrosion current densities, respectively. Corrosion parameters
corrosion rate and inhibition efficiency (E %) were calculated including corrosion current density (Icorr), corrosion potential
w
19
from eqn (1) and (2), respectively:
Scheme 2 Synthetic route for the three gemini surfactants (GS2, GS6 and GS10).
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corr), cathodic and anodic Tafel slopes (b
Paper
(E
c
and b
a
) are obtained
ꢀ The aromatic proton (c) has the value (6.969 ppm), whereas
by extrapolating the linear parts of cathodic and anodic Tafel the aromatic protons (d) have the chemical shis of 6.843 ppm.
20
curves to the point of intersection. The effect of temperature Both of the two types showed doublet spin multiplicity.
was studied using polarization technique throughout
ꢀ Protons of the type (e), attached directly to nitrogen atom,
a temperature range of 283–313 K. The potential of zero charge have the value of 4.274.
pzc) is recorded as a relation between potential and capaci-
ꢀ In the case of protons (f), the chemical shi appears at
tance giving a plot having a shape of a downward parabola 3.864 ppm.
(
2
3
whose minimum represents pzc. The potential is scanned over
ꢀ The d value of (g) protons is 1.703 ppm.
the range from ꢁ0.8 to ꢁ0.6 V (vs. SCE).
ꢀ In case of four protons (h), d value is 1.187 ppm.
ꢀ
The highly shielded protons of the monomer have the value
of 0.812 ppm.
3
.1.2. The gemini surfactants. The mass spectrum of GS2
2
.5. Surface analysis
+
(
Fig. S4†) shows a base peak at m/z ¼ 136.92 [(C
3 2 3 5 10
N H )C H ]
2.5.1. SEM and EDX. Surface morphology of carbon steel
and other signicant peaks some of them are shown at m/z:
immersed in blank and inhibited solutions of oileld water is
investigated using Scanning Electron Microscopy (SEM) and
Energy Dispersive X-ray (EDX). Then, the surface morphology of
carbon steel coupons is scanned using FE-SEM Model Quanta
+
+
6
8.98 [CH
2
CHCH
2
CH
2
CH
2
] , 81.99 [(C
[(C
)] , 179.06 [(C
3
N
2
H
3
)CH
12] ,
3
] , 123.03
+
+
[
[
[
(C
(C
3
3
N
N
2
2
H
H
3
)C
4
H
8
] ,
[(C
151.03
3
N
2
H
3
)C
6
H
162.01
+
+
3
)(CH
2
)
2
3
N
2
H
3
3
N
2
H
3
)C
8
H
16] , 193.02
+
+
(C N H )C H ] , 207.07 [(C N H )C H ] , 235.08 [(C N H )
3
2
3
+
9
18
3
2
3
10 20
+
3
2
3
2
50 attached with EDX (Energy Dispersive X-ray) unit, FEI
Company, Netherlands.
.5.2. FT-IR. FT-IR analysis is performed for corrosion
C H ] , and 236.13 [(C N H )C H ] . The molecular ion peak
1
2
24
3
2
3
12 25
+
appears at m/z of 660 [C H (C N H ) C H Br ] .
1
2
25
3
2
3 2 12 25
2
2
Fig. S5 through Fig. S7† display the FT-IR spectra of GS2, GS6
and GS10. The FT-IR absorption bands of the prepared gemini
surfactants are listed in Table S1† and can be discussed as
products scratched from surface of C-steel immersed in
inhibited solutions and compared with FT-IR spectra of crude
inhibitors to conrm the occurrence of adsorption of inhibitors
molecules on C-steel surface. FT-IR analysis was performed
using KBr pellets via Perkin Elmer, Spectrum One FT-IR
spectrometer.
following:
24
ꢁ1
ꢀ
N–H stretching bands (broad) appear at: 3417 cm ; GS2,
ꢁ1
ꢁ1
3
416 cm ; GS6 and 3419 cm ; GS10 due to the presence of the
+
carbene proton in the form of NH (Scheme 2).
Aromatic C–H stretching bands appear at: 3039 cm
ꢁ
1
ꢀ
ꢁ1
ꢁ1
(
GS2), 3073 cm (GS6) and 3070 cm (GS10).
Aliphatic C–H stretching bands appear at: 2922–2852 cm
ꢁ1
ꢀ
3
3
. Results and discussion
.1. Characterization of the synthesized gemini surfactants
ꢁ1
ꢁ1
(
GS2), 2924–2854 cm (GS6) and 2923–2853 cm (GS10).
ꢁ1
ꢀ
C]C stretching bands appear at: 2042 cm
(GS2),
ꢁ
1
ꢁ1
3
.1.1. The intermediate compound. The mass spectrum of 2062 cm (GS6) and 2055 cm (GS10).
ꢁ1
the intermediate compound (Fig. S1†) shows a base peak at m/z
ꢀ C–C stretching bands appear at: 1563 cm
(GS2),
+
.
ꢁ1
ꢁ1
¼
81.99 [(C
3
N
2
H
3
)CH
3
]
and other signicant peaks some of 1625 cm (GS6) and 1623 cm (GS10).
+
ꢁ1
them are shown at m/z: 68.98 [CH
2
CHCH
2
CH
2
CH
2
] , 123.03
ꢀ C–Br (ionic bond) bands appear at: 635.7 cm (GS2),
+
+
ꢁ1 ꢁ1
[
(C N H )C H ] , 136.92 [(C N H )C H ] , 151.03 [(C N H ) 634.9 cm (GS6) and 634.8 cm (GS10).
3
2
3
4
8
3
2
3
+
5
10
3
2
3
+
+
1
C H ] , 179.06 [(C N H )C H ] , 193.02 [(C N H )C H ] ,
2
Fig. S8 through Fig. S10† demonstrates the H -NMR spec-
07.07 [(C N H )C H ] and 235.08 [(C N H )C H ] . The trum of GS2, GS6 and GS10. The chemical shis of H -NMR
molecular ion peak appears at m/z of 236.13 [(C N H )C12H25] . spectra for different types of protons in the three gemini
3 2 3
6
12
3
2
3
8
16
3
2
3
9
+
18
+
1
3 2 3 10 20 3 2 3 12 24
+
Fig. S2† displays the FT-IR spectrum of the intermediate surfactants (Fig. S11†) are listed in Table S3† and we can
compound. Its FT-IR absorption bands are listed in Table S1† observe the following:
and can be discussed as following:
ꢀ The proton (a), [compounds GS2, GS6 and GS10], has high
ꢁ1
ꢀ
ꢀ
ꢀ
Aliphatic C–H stretching bands appear at 2923–2854 cm .
Aromatic C–H stretching bands appear at 3099 cm
chemical shi (10.168, 10.177 and 10.323 ppm, respectively).
ꢁ
1
.
This could be attributed also to the presence of the carbene
ꢁ
1
+
N–H stretching bands (broad) appear at 3407 cm . This proton in the form of NH .
could be attributed to the presence of the carbene proton in the
ꢀ The same protons (b) [with the values of 8.409, 9.375 and
+
form of NH (Scheme S1†).
9.274 ppm], possess the carbene type.
ꢁ
1
ꢀ
C]C stretching bands appear at 2028 cm
.
ꢀ The aromatic protons (c) have the values (7.376, 7.453 and
7.421 ppm), whereas the aromatic protons (d) have the chemical
ꢁ1
ꢀ
C–C stretching bands appear at 1563 cm
.
1
Fig. S3† demonstrates the H -NMR spectrum of the inter- shis of 7.270, 7.272 and 7.271 ppm. Both of the two types
mediate compound. From the data listed in Table S2,† we can showed doublet spin multiplicity.
+
observe the following:
ꢀ Protons of the type (e), attached directly to N , have the
ꢀ
The proton (a) has a high chemical shi which could be values of 4.534, 4.308 and 4.335 ppm respectively. The spin
attributed to the presence of the carbene proton.
multiplicity of (e) proton is triplet.
ꢀ
The same protons (b) [with the value of 7.436 ppm],
possesses the carbene type.
ꢀ In case of compound GS2, the four protons (f) possess (d)
value of 4.202 ppm (triplet). Whereas the four (f) protons of
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compounds GS6 and GS10 have the values of 4.248 and solutions in absence and presence of the three synthesized
.370 ppm with triplet spin multiplicity and the four (f*) gemini surfactants, GS2, GS6 and GS10 at ambient temperature.
protons possess (d) values of 4.283 and 3.393 ppm respectively Table 3 reveals that the corrosion rate of C-steel immersed in
with multiplet spin multiplicity. oileld water containing GS2, GS6 or sGS10 decreases with
The (d) value of the four multiplet (g) protons in (GS2) is increasing their concentration (up to critical values). This
.094 ppm. In the case of GS6 and GS10, the eight (multiplet g) behavior can be attributed to the increase in the number of
protons are approximately equal and possess 3.462 and surfactant molecules adsorbed at metal/solution interface on
3
ꢀ
4
2
.568 ppm respectively.
In case of four protons (h) of GS2 and GS6, d values are surfactants constitute adsorption lms on C-steel surface which
.881 and 1.854 ppm respectively with multiplet spin multi- protects it against corrosive species. The maximum E % values
increasing its concentration. So, molecules of the gemini
ꢀ
1
w
plicity. While in GS10, the twelve protons possess 1.844 ppm for the three gemini surfactants are 67.64% at 200 ppm GS2,
with multiplet multiplicity. 62.30% at 300 ppm GS6 and 85.21% at 150 ppm GS10. The
The 32 protons (i) for GS2, GS6 and GS10 have the values of decrease in the corrosion rate of C-steel in oileld water in
.273, 1.383 and 1.235 ppm respectively, with multiplet presence of these gemini surfactants conrms that their mole-
ꢀ
1
2
0
multiplicity.
cules have adsorbed on C-steel surface.
3.2.2. EIS measurements. EIS is an effective technique
the values of 0.838, 0.811 and 0.842 ppm respectively with utilized for studying the corrosion behavior of protected and
ꢀ
The highly shielded six protons of GS2, GS6 and GS10, have
25
triplet spin multiplicity.
bare carbon steel. EIS spectra for solutions containing any
Table S4† illustrates the results of elemental analysis where gemini surfactant show some deviations from the ideal
the observed results are in good agreement with the calculated
ones. The thermal stability of the three prepared gemini
surfactants was assessed using thermogravimetric analysis
(
2
TGA). Fig. S12† shows that the three surfactants are stable up to
50 C and completely lose their weights at 340 C. Both GS6
ꢂ
ꢂ
and GS10 have comparable thermal stability but the gemini
surfactant of shortest spacer (GS2) has showed a slight increase
in the degradation temperature in comparison to both GS6 and
GS10.
3
.2. Effect of inhibitor concentration
.2.1. Weight loss measurements. Gravimetric (chemical)
method is utilized for evaluating the corrosion rate and inhi-
bition efficiency (E %) for carbon steel in oileld water
3
w
Table 3 Weight loss rate and inhibition efficiency calculated from
gravimetric measurements for C-steel in oilfield water as a function of
gemini surfactant concentration at room temperature for one week
Concentration
(ppm)
Weight loss rate
ꢃ 10 (mg cm
3
ꢁ2 ꢁ1
Inhibitor
h
)
w
E %
Blank
GS2
—
50
5.30
4.16
1.98
1.83
1.72
1.75
1.75
4.79
3.46
3.29
3.12
2.65
3.02
2.04
0.85
0.78
0.85
0.98
1.27
—
21.49
62.69
65.47
67.64
67.04
67.05
17.89
34.76
37.93
41.13
62.30
43.05
61.53
83.98
85.21
1
1
2
3
4
00
50
00
00
00
GS6
50
1
1
2
3
4
00
50
00
00
00
GS10
50
1
1
2
3
4
00
50
00
00
00
83.96
81.52 Fig. 2 EIS spectra for C-steel in oilfield water as a function of GS2
76.01 concentration at 293 K in the Bode format (a) and Nyquist format (b).
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capacitive behavior recorded in any tested solution. As an water inhibited by gemini surfactants, the straight line
example, Bode plot for GS2 (Fig. 2(a)) displays a two-time appearing at LF region in blank solution turns to take the shape
constant behavior where the resistive part at LF region in of an arc whose angle increases with inhibitor concentration
Bode plot doesn't appear and F doesn't reach 0 although the (till a critical value) due to the increase in the degree of surface
29
spectra was measured down to 0.01 Hz. Two-time constant coverage (q) by inhibitor molecules. Above the critical
behavior may be attributed to roughness and other inhomoge- concentrations, the arcs are lowered again indicating that
26
neity of solid surface. Moreover, Nyquist format (Fig. 2(b)) corrosion protection has decreased again. EIS spectra for GS6
shows no ideal capacitive semicircles but each plot displays two and GS10 are shown in ESI data (Fig. S13 through Fig. S16†).
incomplete semicircles: the rst one, at high frequency (HF)
region appearing as a part of small loop linked to another large the equivalent circuit depicted in Fig. 3 was found to give
In an attempt to analyze the experimental impedance data,
30
incomplete one at low frequency region (LF) and deects a satisfactory tting result with a maximum average error 0.3%.
upward giving to a slightly inclined line or an arc. This feature In this electrical model, two constant phase elements (Q and
1
21
27
refers to Warburg impedance due to diffusion process. For
2
Q ) are used instead of the two real capacitances to give the best
more clarication, Nyquist spectrum for the blank solution is tting. For a rough or porous surface, non-homogeneity can
displayed in the inset. The arcs that have appeared in the cause the double layer capacitance to appear as a constant
31
Nyquist plots represent parts of depressed semicircles whose phase element. This model consists of two-time constants
centers are located beneath the real axis. This behavior is ((Q W) and (Q )) parallel to each other and all in series to
characteristic for solid electrodes and is oen referred to as the solution resistance (R ). The rst time constant (Q R W)
1
R
1
2 2
R
s
1 1
frequency dispersion and occurs due to surface roughness, expresses the behavior at LF region and is attributed to the
2
8
impurities or dislocations. Surface roughness is attributed to adsorbed lm while the other one (Q R ) is related to the HF
2
2
22
the eating away of local sites on electrode surface. For oileld region and describes the behavior of the double layer at the base
of pores or defects in the lm. The constant phase element has
a non-integer parameter called the phase shi (n) which is used
to compensate the system heterogeneity. So, the phase shi (n)
can be described as a degree of surface roughness or non-
32
homogeneity.
Investigating the simulated data listed in Table 4 illustrates
the following important points:
s
(a) The solution resistance (R ) is low and nearly remains
constant either in the absence or presence of inhibitors (ranges
2
between 1.11 and 1.61 U cm ) due to good conductivity of all
33
tested solutions.
Fig. 3 The equivalent circuit.
Table 4 Electrochemical impedance parameters and inhibition efficiency calculated for C-steel in oilfield water as a function of gemini
surfactant concentration at 293 K
W
2
ꢁ0.5
2
ꢁ2
2
ꢁ2
2
Inhibitor
C (ppm)
(U cm s
)
R
1
(U cm )
Q
1
(mF cm
)
n
1
R
2
(U cm )
Q
2
(mF cm
)
n
2
R
s
(U cm )
i
E %
Blank
GS2
—
50
66.23
24.74
7.5
491.34
1010.04
1056.21
1181.33
1726.53
1574.06
1529.88
654.08
100.21
136.81
252.32
306.00
314.21
280.67
255.05
62.67
104.14
118.91
215.16
132.04
182.46
207.47
177.05
131.65
129.4
0.47
10.10
14.25
12.41
12.52
11.39
11.63
11.75
17.12
13.47
13.86
21.79
15.04
19.31
14.09
19.93
22.54
20.09
25.95
22.65
68.11
62.21
71.44
72.32
69.02
71.33
70.25
51.75
47.65
50.98
57.26
45.65
55.96
58.42
54.81
51.79
52.35
48.25
49.26
0.82
1.13
1.2
—
0.537
0.585
0.609
0.601
0.591
0.611
0.42
0.484
0.498
0.556
0.501
0.534
0.6
0.836
0.815
0.819
0.819
0.806
0.814
0.804
0.753
0.777
0.725
0.749
0.746
0.79
51.05
53.08
58.00
71.15
68.38
67.47
25.29
38.57
50.21
63.77
64.40
59.11
54.73
66.38
74.60
71.66
69.78
67.24
1
1
2
3
4
00
50
00
00
00
1.29
1.11
1.20
1.33
1.32
1.29
1.35
1.57
1.59
1.16
1.61
1.27
1.28
1.36
1.37
1.33
1.15
7.21
11.39
30.75
35.23
150.08
27.87
128.14
1.85
740.15
2.62
7.46
GS6
50
1
1
2
3
4
00
802.85
993.23
1362.3
50
00
00
00
1393.65
1206.98
1093.55
1471.74
1951.4
1749.33
1633.34
1507.94
GS10
50
1
1
2
3
4
00
10.66
75.13
74.53
9.1
0.61
0.58
0.58
0.62
0.79
0.79
0.82
0.8
50
00
00
00
161.19
121.37
48.22
0.57
0.82
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b) The resistance (R
adsorbed lm resistance (R ) is generally with much higher
values than those for R2 representing the charge transfer
RSC Advances
(
1
) denoting to the resistance of the Table 5 Electrochemical corrosion parameters and inhibition effi-
ciency calculated for C-steel in oilfield water as a function of gemini
f
surfactant concentration at 293 K
2
resistance (R ). R possesses a value of 10.01 U cm (in blank
ct
2
Conc. Icorr
oileld water) and slightly increases up to a maximum value of Inhibitor (ppm) (mA cm
Ecorr
(V)
b
b
c
a
ꢁ2
ꢁ1
ꢁ1
)
(V dec.
)
(V dec.
)
Ep%
2
2
1
4.25 U cm in presence of GS2, 21.79 U cm in presence of GS6
2
Blank
GS2
—
50
95.37
52.42
45.39
37.28
28.67
31.34
32.20
67.93
56.64
43.12
35.98
35.31
36.58
34.27
26.22
18.36
23.26
24.34
28.88
ꢁ0.825 0.185
ꢁ0.836 0.175
ꢁ0.831 0.145
ꢁ0.844 0.127
ꢁ0.847 0.090
ꢁ0.842 0.107
ꢁ0.828 0.134
ꢁ0.861 0.195
ꢁ0.872 0.175
ꢁ0.878 0.140
ꢁ0.880 0.126
ꢁ0.890 0.108
ꢁ0.887 0.047
ꢁ0.823 0.161
ꢁ0.823 0.164
ꢁ0.821 0.118
ꢁ0.815 0.147
ꢁ0.822 0.169
ꢁ0.817 0.176
ꢁ0.107
ꢁ0.123
ꢁ0.112
ꢁ0.098
ꢁ0.084
ꢁ0.091
ꢁ0.101
ꢁ0.113
ꢁ0.099
ꢁ0.086
ꢁ0.077
ꢁ0.070
ꢁ0.039
ꢁ0.122
ꢁ0.123
ꢁ0.105
ꢁ0.125
ꢁ0.128
ꢁ0.134
—
and 25.95 U cm in presence of GS10. So, the change in R
signicant.
2
is not
45.03
52.41
60.91
69.93
67.14
66.24
28.77
40.61
54.79
62.28
62.98
61.65
64.06
72.51
80.75
75.61
74.47
69.71
1
1
00
50
(c) Upon increasing the concentration of any gemini
surfactant, a continuous signicant increase in R1 value is
200
300
400
50
2
observed. In the blank solution, R ¼ 491.34 U cm but R1
1
2
increases to 1726.53 U cm (for oileld water inhibited by
2
GS6
2
3
1
00 ppm GS2), 1393.65 U cm (for solution inhibited by
00 ppm GS6) and 1951.40 U cm (for solution inhibited by
50 ppm GS10). Above these concentrations, R
1
1
00
50
2
1
suffers a small
200
300
decrease in its value.
d) Comparing the values of the heterogeneity parameter (n)
indicates that n < n . The value of n (relating to the adsorbed
400
(
GS10
50
1
2
1
1
1
00
50

lm) increases from 0.47 in the blank solution and reaches
maximum values of 0.61, 0.56 and 0.62 in presence of GS2, GS6
and GS10, respectively. On the other hand, the values of n
relating to the double layer at the metal/native lm interface)
200
300
2
400
(
nearly remains constant in all cases. These indications suggest
that the C-steel surface contains voids and pores and the pres-
ence of gemini surfactants leads to reduction in surface
roughness due to the adsorption of their molecules on
31
adsorption sites of the C-steel surface.
.2.3. Potentiodynamic polarization
3
measurements.
Potentiodynamic polarization measurements can provide
important information about the kinetics of cathodic and
20
anodic corrosion reactions.
Electrochemical corrosion
parameters involve the corrosion potential (Ecorr), corrosion
current density (Icorr), as well as the anodic and cathodic Tafel
constants (ba and b ), respectively. These parameters were
c
derived from Tafel polarization curves (E–log I) for carbon steel
immersed in oileld water solutions in the absence and pres-
ence of gemini surfactants and their values are listed in Table 5.
As an example, Tafel curves of GS2 are shown in Fig. 4. Tafel
curves for GS6 and GS10 are presented in ESI materials (Fig. S17
and S18,† respectively). Icorr values are obtained from the
Fig. 4 Polarization curves for carbon steel in oilfield water as a func-
intersection between the extrapolations of linear regions of the tion of GS2 concentration at 293 K.
anodic and cathodic branches in the Tafel polarization plot
provided that the intersection point corresponds to E
(the
corr
34
potential at which Icorr is minimum). Investigating Table 5 inhibitor according to the direction of the potential shi
yields the following information:
either to the more negative or to the more positive direction,
1) Icorr values decrease with the increase in concentrations respectively. If the displacement in Ecorr is <85 mV, the inhibitor
(
20
of gemini surfactants till their critical values (200 ppm for GS2, can be classied as a mixed-type inhibitor. So, GS2 and GS6
00 ppm for GS6 and 150 ppm for GS10). Aer that, Icorr re- are mixed-type inhibitors with major cathodic effectiveness,
increases again because the surface becomes slightly bare and while GS10 is a mixed type inhibitor but with a predominant
3
vulnerable to corrosion attack.
anodic effect.
(2) For GS2, the maximum displacement in Ecorr is about
(3) Both anodic and cathodic Tafel slopes (b and b ) are
a
c
ꢁ
22 mV relative to Ecorr recorded in the blank solution. For GS6, changed signicantly for all gemini surfactants which conrms
the maximum Ecorr displacement is about ꢁ65 mV, while GS10 that these inhibitors affect mechanisms of both cathodic and
35
shows a maximum displacement in Ecorr of about +10 mV. By anodic reactions (they belong to mixed-type inhibitors), where
convention, if the magnitude of Ecorr displacement in the the displacement in the values of Tafel slopes is attributed to
20
presence of inhibitor is >ꢄ 85 mV with respect to Ecorr in blank a change in reaction mechanism.
solution, the inhibitor is classied as cathodic or anodic-type
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The inhibition efficiency values increase as a function of
(b) Above the optimum concentration, the number of
concentration of gemini surfactants till certain values. Above surfactant molecules becomes so much that electrostatic
these critical concentrations, the inhibition efficiency values interactions between them force the initially adsorbed mole-
start to decrease again with increasing concentration. There are cules (in their parallel position) to change their mode of
two suggestions for explaining this behavior:
adsorption to allow more number of molecules to adsorb on the
36
1
Mu et al. have studied the inhibitive effect of sodium metal surface. So, gemini surfactant molecules adsorb on the
dodecyl sulfonate (SDS) on mild steel in 2 M HCl and found that surface in a perpendicular position (with respect to C-steel
the maximum inhibition efficiency was obtained at 150 ppm surface) to permit steel surface to be attached to more and
and the inhibition efficiency decreases when surfactant more surfactant molecules. Accordingly, the surface area occu-
concentration increases above this value. They explained this pied by surfactant molecules, despite their huge number,
behavior in a manner that at the high concentration range, SDS becomes lower than before. So, corrosive species have the
adsorbed on the steel surface may form hemi-micelles through chance again to attack the steel surface and hence the corrosion
the interaction between their hydrophobic groups and these rate increases again (Fig. 5(c)).
hemi-micelles are similar in structure to the normal micelles.
3.2.4. Surface tension measurements. Generally, the rela-
According to this attitude, high concentrations of gemini tionship between the surface tension and the concentration
surfactants lead to aggregation of their molecules which may added from each tested gemini surfactant (Fig. S19†) reveals an
lead to the desorption of some initially adsorbed ones.
initial sharp decrease in the surface tension of the oileld water
37
2
Jiang et al. have proposed another mechanism for the solution. This is followed by a slighter decrease in the surface
decrease in the inhibition efficiency values above an optimum tension value as the GS concentration is further increased
or a critical concentration based on the adsorption mode of which ends nally with a plateau. Just at the beginning of this
surfactant molecules on steel surface as follows (Fig. 5):
plateau the critical micelle concentration (CMC) is attained.
(a) Below or at the optimum concentration surfactant CMC is the lowest concentration at which micelles (surfactant
molecules adsorb on steel surface in a parallel position (with aggregations) begin to form. When micelles are formed, the
respect to C-steel surface). As the surfactant concentration repulsion forces between the head groups of surfactant mole-
increases, more surfactant molecules adsorb on the steel cules constructing the micelle are balanced by hydrophobic
surface leading to covering more active sides on the steel attractions between chains. For ionic micelles, these forces are
surface. When concentration reaching the optimum value, steel balanced also by attractions between head groups and counter
15
surface becomes covered with surfactant molecules to its ions. Herein, CMC values for GS2, GS6 and GS10 are approx-
maximum extent (Fig. 5(b)). imately 300, 300 and 200 ppm, respectively. It is obvious that the
Fig. 5 Adsorption mechanism of gemini surfactant on carbon steel surface.
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maximum inhibition efficiency is below or just at the CMC
values at which micelles begin to form. Aer CMC, the inhibi-
tion efficiency decreases as surfactant molecules start to leave
the carbon steel surface offering a chance for the corrosive
species to re-attack the bare region on the steel surface.
3.2.5. Adsorption isotherms. Since the metal surface in
aqueous solutions is always covered with adsorbed water
molecules, the adsorption of inhibitor molecules from the
aqueous solution can be considered as a quasi-substitution
process between the inhibitor molecules in the aqueous
phase, Inh(sol), and the water molecules at the metal surface,
38
H O(ads):
2
Inh(sol) + xH
2
O
(ads) / Inh(ads) + xH
2
O
(sol)
(5)
where x represents the number of water molecules replaced by
one molecule of organic inhibitor. Corrosion inhibition is
a
surface process based on the adsorption of organic
39
compounds on the metal surface. The presence of chemically
stable and surface active inhibitor molecules increases the
energy of activation for iron dissolution reaction and leads to
diminishing its surface area available for corrosion attack.
The mechanism of corrosion inhibition can be thus
explained on the basis of adsorption principle and the nature
of the interaction between the inhibitor and C-steel surface can
be understood using an adsorption isotherm. Assuming that
the gemini surfactants reduce the rate of corrosion process
mainly through the increase in the degree of C-steel surface
coverage (q) by surfactant molecules, the inhibition efficiency
40
41
42
ꢁ2
22
can be considered as a function of q, i.e. q ¼ 10 ꢃ E%.
Frumkin, Freundlich, Temkin, Flory–Huggins and Langmuir
adsorption isotherms have been attempted for tting the
adsorption of molecules of GS2, GS6 and GS10 on C-steel
surface in oileld water. It was found that the Langmuir
model have showed the best tting where it had the highest
2
values of regression factor, r . Langmuir isotherm is repre-
C
q
40,43
sented with a relation between and C according to eqn (6):
C
1
¼ K þ C
(6)
q
ads
where Kads is the adsorption–desorption equilibrium constant.
Langmuir isotherm assumes that the solid surface contains
a xed number of adsorption sites and each site holds one
Fig. 6 Langmuir adsorption plots for carbon steel in oilfield water
inhibited by gemini surfactants based on data from weight loss (a), EIS
22
adsorbed species and there are no interactions between the
40
adsorbed molecules on the metal surface. Langmuir plot is
drawn based on the data obtained from weight loss, EIS and
polarization techniques (Fig. 6) and the change in free energy of
adsorption (DGads) is calculated according to the following
(b) and polarization (c).
the adsorption will be physical (known as physisorption) which
44
equation:
occurs via electrostatic interactions. (ii) If DGads is more nega-
ꢁ
1
tive than ꢁ40 kJ mol the adsorption is chemical (known as
chemisorption) where coordinate bonds are formed via electron
transfer from inhibitor molecules to the metal surface. (iii) But, if
6
DGads ¼ ꢁRT ln(10 Kads
)
(7)
6
where the factor 10 represents the concentration of water
ꢁ
1
ꢁ1
the DGads is between ꢁ20 and ꢁ40 kJ mol then both types of
molecules in the solution (in mg l ) and R is the universal gas
38
ꢁ
1
ꢁ1
adsorption are involved. For GS2, GS6 and GS10, DGads values are
constant (8.314 J K mol ). DGads values are depicted in Table
ꢁ
1
ranging between ꢁ20.58 and ꢁ30.44 kJ mol which indicate the
6
. The value of DGads determines the nature of adsorption
ꢁ1
occurrence of both physisorption and chemisorption processes
process such that: (i) if DGads is less negative than ꢁ20 kJ mol
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Table 6 Langmuir adsorption parameters for the adsorption of gemini
surfactants on C-steel surface in oilfield water at 293 K
DG
(kJ mol )
2
ꢁ1
ꢁ1
Inhibitor
GS2
Technique
r
K
ads (ppm
)
Weight loss
EIS
Tafel polarization
Weight loss
EIS
Tafel polarization
Weight loss
EIS
0.9995
0.9806
0.9882
0.9271
0.9591
0.9793
0.9877
0.9930
0.9947
0.107
0.022
0.020
0.005
0.007
0.009
0.267
0.079
0.195
ꢁ28.20
ꢁ24.39
ꢁ24.17
ꢁ20.58
ꢁ21.50
ꢁ22.14
ꢁ30.44
ꢁ27.47
ꢁ29.67
GS6
GS10
Tafel polarization
45
with the predominance of the former mode. The negative values
of DGads for adsorption of all gemini surfactants on C-steel implies
46
the spontaneity and stability of adsorption process.
3.3. Effect of temperature
The effect of temperature on corrosion rates of C-steel and its
impact on the stability of the protective lm in oileld water in
the absence and presence of gemini surfactants were studied
electrochemically using the potentiodynamic polarization
method over the temperature range 283–313 K. Fig. 7 reveals
that the C-steel potential either in the blank or inhibited solu-
tions is shied towards more negative values with time and the
E
ss value is shied also towards the more negative direction as
Fig. 7 Variation of C-steel potential in oilfield water free from inhibi-
tors (a) and containing 300 ppm GS2 (b) with time at different
temperatures. Inset: change in Ess of C-steel in oilfield water with
temperature.
temperature increases but the shi in Ess value is more signif-
icant for blank solution than in the presence of inhibitors. This
could be attributed to the effect of adsorption layer which can
slightly isolate the C-steel surface from the corrosive medium.
Fig. 8 shows that the magnitude of corrosion current density
(
Icorr) increases as temperature is raised either for the inhibited
ꢁ1
ꢁ1
13.59 kJ mol
2
(in blank oileld water) to 22.37, 17.70 and
or uninhibited solutions of oileld water. Nevertheless, Table 7
reveals that the change in Icorr between 283 and 313 K in oileld
water solutions containing GS2, GS6 or GS10 is small (ꢅ31, 26
4.92 kJ mol , respectively. This indicates that the energy
barrier for the corrosion reaction has been raised and hence the
corrosion inhibition is enhanced.
oileld water inhibited by GS2 and GS10 are over 20 kJ mol
indicating that the inhibition process is under surface reaction
47
E
a
values for solutions of
ꢁ
2
and 26 mA cm , respectively) in comparison to that of blank
ꢁ1
ꢁ2
oileld water (ꢅ51 mA cm ) which could be also related to the
isolating effect of adsorption lms of gemini surfactants. The
22
control.
rate of change in Ess is coincident with the rate of change in Icorr
Analysis of the dependence of inhibition efficiency on
temperature as well as the comparison of corrosion activation
energies in the absence and presence of an inhibitor give useful
information about the mechanism of inhibitor adsorption.
Upon elevating the ambient temperature a simultaneous
decrease in the inhibition efficiency together with a concurrent
which conrms that adsorption lms maintain their stability
and protective effect even at elevated temperatures.
Thermodynamic activation parameters have an important
role in understanding the inhibitive mechanism of organic
additives. The apparent activation energy associated with C-
steel corrosion in free and inhibited solutions of oileld water
was determined using Arrhenius plot (Fig. 9(a)) according to the
22
a
increase in corrosion activation energy (E ) in presence of
inhibitor compared to its absence conrms the formation of an
adsorption lm of physical nature (electrostatic). On the other
hand, the increase in inhibition efficiency with raising
temperature accompanied with a decrease in activation energy
in the presence of inhibitor suggests a chemisorption mecha-
nism. Physical adsorption arises by electrostatic interaction,
while chemical adsorption occurs through a bond formation by
sharing an electron. So, these gemini surfactants adsorb
24
following equation:
(
ꢁE
a
/RT)
I
corr ¼ Ae
(8)
a
where E is the apparent activation energy, A is Arrhenius factor,
48
T is the absolute temperature and R is the universal gas
constant. Table 8 shows that the apparent activation energy (Ea)
obtained from Arrhenius plots has increased for solutions of
oileld water inhibited by GS2, GS6 and GS10 from
49
mainly via physical adsorption on C-steel surface.
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Fig. 8 Polarization curves for carbon steel in oilfield water free (a) and
containing 300 ppm GS2 (b) at different temperatures.
Table 7 Corrosion kinetic parameters for carbon steel in oilfield water
in absence and presence of 300 ppm of each gemini surfactant as
a function of temperature
Temperature Icorr
Inhibitor (K) (mA cm ) (V)
E
corr
b
a
b
c
ꢁ2
ꢁ1
ꢁ1
p
(V dec. ) (V dec. ) E %
Fig. 9 Arrhenius plot (a) and transition state plot (b) for carbon steel in
oilfield water in absence and presence of GS2, GS6 and GS10.
Blank
GS2
283
63.58
95.37
101.05
114.70
20.00
31.34
38.78
51.09
23.51
35.31
42.11
49.12
14.71
24.34
34.27
40.24
ꢁ0.793 0.239
ꢁ0.132
ꢁ0.107
ꢁ0.121
ꢁ0.569
ꢁ0.139
ꢁ0.099
ꢁ0.096
ꢁ0.112
ꢁ0.109
ꢁ0.070
ꢁ0.102
ꢁ0.082
ꢁ0.117
ꢁ0.128
ꢁ0.134
ꢁ0.141
—
—
—
—
2
3
3
93
03
13
ꢁ0.824 0.185
ꢁ0.825 0.135
ꢁ0.827 0.057
ꢁ0.813 0.158
ꢁ0.842 0.129
ꢁ0.831 0.128
ꢁ0.847 0.171
ꢁ0.811 0.139
ꢁ0.890 0.108
ꢁ0.848 0.153
ꢁ0.815 0.079
ꢁ0.809 0.131
ꢁ0.822 0.169
ꢁ0.806 0.174
ꢁ0.802 0.169
!
*
ꢁ
DH*
67.14 2:303R
R
DS
283
68.54
and its intercept represents log
þ
NAh 2:303R
where
2
3
3
93
03
13
61.62
54.20
63.02
ꢁ34
h is Planck's constant (6.626 ꢃ 10
A
J s), N is Avogadro's
number (6.022 ꢃ 10 mol ), R is the general gas constant
2
3
ꢁ1
GS6
283
ꢁ1
ꢁ1 24
2
3
3
93
03
13
62.98 (8.314 J K mol ).
58.33
57.17
76.87
74.47
66.09
64.91
ꢀ
ꢁ
*
*
I
corr
R
DH
DS
log
¼ log N ꢁ
þ
(9)
T
A
h
2:303RT 2:303R
GS10
283
2
3
3
93
03
13
The DH* values of activation for the dissolution reaction of
C-steel surface in oileld water in the presence of GS2, GS6 and
ꢁ
1
GS10 are high (19.89, 15.22 and 22.44 kJ mol , respectively) in
ꢁ
1
Thermodynamic parameters of activation, enthalpy change
comparison to that in absence of inhibitors (11.12 kJ mol ).
The positive signs of DH* reect the endothermic nature of C-
steel dissolution activated process which suggests the slow
(DH*) and entropy change (DS*), were calculated from eqn (9)
ꢀ
ꢁ
Icorr
using log
vs: T plot (Fig. 9(b)) where its slope equals
T
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Table 8 Activation parameters for carbon steel in oilfield water in decrease with time. These results indicate that in blank oileld
absence and presence of 300 ppm GS2, GS6 and GS10
water, the continuous increase in corrosion rate during the
initial days of immersion could be due to the dissolution of the
air-oxide lm formed before immersion. In the meantime, the
DH*
(kJ mol
DS*
(J mol
ꢁ
1
2
ꢁ1
ꢁ1 ꢁ1
2
Inhibitor
E
a
(kJ mol
)
r
)
K
)
r
prevailing corrosive species aggressively attack the C-steel and
Blank
GS2
GS6
13.59
22.37
17.70
24.92
0.8731 11.12
0.9813 19.89
0.9529 15.22
0.9626 22.44
ꢁ170.01
ꢁ148.93
ꢁ163.94
ꢁ142.29
0.8198 corrosion products (Fe oxides and salts) accumulate on its
0.9760
surface with time forming a somewhat protective lm which
0.9363
33
slightly isolates the C-steel surface from the medium. Aer
longer immersion time, the amount of corrosion products
becomes so much that the aggressive species can hardly attack
the metal surface. So, the corrosion process continues but with
a decreasing rate. For solutions of oileld water inhibited by
gemini surfactants, the corrosion rate was found to be contin-
uously decreasing with time due to the inhibitive contribution
between adsorption lm and corrosion products. With pro-
longing immersion time, more surfactant molecules come in
the vicinity of C-steel surface and adsorb on it until the surface
is covered with surfactant molecules to its maximum value.
Aer that, surfactant molecules can form multilayers over the
surface leading to more enhanced adsorption lm and the
GS10
0.9753
38
dissolution of C-steel surface in presence of inhibitors. Large
and negative values of DS* show that the activated complex in
the rate determining step represents an association rather than
a dissociation step, meaning that a decrease in disordering or
randomness takes place on going from reactants to the acti-
vated complex (molecules are in higher ordered state in the
22
activated complex than in the initial state). Comparing the
entropy of activation in both inhibited and uninhibited oileld
water reveals that the values of DS* are less negative in solutions
containing GS2, GS6 and GS10 (ꢁ148.93, ꢁ163.94 and ꢁ142.29 J
50
corrosion process becomes more inhibited.
ꢁ
1
ꢁ1
mol
K
, respectively) than for uninhibited solution (ꢁ170.01
ꢁ1
ꢁ
1
J mol
K ). The thermodynamic values obtained for DS* are
the algebraic sum of the adsorption of inhibitor molecules 3.5. Inhibition mechanism
(
solute) and desorption of water molecules (solvent). Hence, the
increase in entropy of activation in presence of gemini surfac-
tants is attributed to the increase in the solvent (H O) entropy as
a result of H O molecules desorbed from C-steel surface.
It is important to determine the potential of zero charge (pzc) of
C-steel in oileld water to know the charge of steel surface and
hence we can explain the adsorption mechanism of gemini
2
38
2
32
surfactants. Values of pzc for the blank and all inhibited
3.4. Effect of immersion time
It is of prime importance to study the effect of immersion time
on corrosion inhibition to examine the stability of the inhibitor

lm with time. Weight loss method was employed to evaluate
the effect of immersion time on the corrosion rate of C-steel up
to four weeks. Fig. 10 shows that oileld water (free from
inhibitor) leads to severe corrosion for C-steel with a corrosion
rate being continuously increased during the rst two weeks.
Aer that, the corrosion rate drops suddenly till the end of the
third week and eventually becomes nearly constant. For C-steel
coupons immersed in oileld water inhibited by any of the three
tested gemini surfactants, the corrosion rate continues to
Fig. 11 Variation of the capacitance as a function of potential applied
Fig. 10 Effect of immersion time on corrosion rate of carbon steel on carbon steel in oilfield water in the absence and presence of gemini
recorded at room temperature. surfactants at 293 K.
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Table 9 Comparison between Ess and pzc
Ess vs.
pzc vs.
Inhibitor
SCE (mV)
SCE (mV)
Blank
GS2
GS6
ꢁ656
ꢁ670
ꢁ656
ꢁ645
ꢁ737
ꢁ760
ꢁ738
ꢁ739
GS10
Fig. 14 HOMO (a) and LUMO (b) distributions in GS6 molecule.
1
ꢁ
22
involved in oxygen reduction; H O + O + 2e ¼ 2OH . Table 2
2
2
2
shows that the corrosive medium under study is slightly acidic
(
pH ¼ 6.85 at 25 ꢂC) so the possible cathodic reactions are
+
35
oxygen reduction and hydrogen evolution; 2H + 2e ¼ H
2
.
Since the C-steel is positively charged either in inhibited or
uninhibited oileld water, the inhibitor molecules can be
adsorbed on the metal/solution interface by one or more of the
38
following ways : (i) donor–acceptor interactions between the
p-electrons of aromatic imidazolium ring and vacant d-orbitals
of iron surface atoms. (ii) Unshared electron pairs of tertiary
imidazolium N atoms and vacant d-orbitals of iron surface
atoms. (iii) Interaction of d-electrons of iron surface atoms and
the positive charge delocalized over the imidazolium ring.
Gemini surfactants may also adsorb on positively charged C-
Fig. 12 Adsorption modes of GS2, GS6 and GS10.
ꢁ
ꢁ
oileld water solutions were calculated from Fig. 11. Table 9 steel surface in a manner that anions (e.g. Cl , Br and
ꢁ
reveals that all pzc values are more negative than their corre- HCO
) adsorb directly on C-steel surface then molecules of
3
35
sponding steady state (E ) values. This means that the C-steel cationic gemini surfactants adsorb on the anionic layer.
ss
15
surface either in the blank or inhibited solutions is positively
According to Heakal and Elkholy, research works that have
charged at the open-circuit conditions. This observation can be studied the effect of spacer revealed two contradictory opinions:
explained such that steels or iron corrode when Fe atoms (i) the inhibition efficiency decreases with increasing the length
decompose from their surfaces into positive ions and electrons; of spacer chain. This behavior has been explained such that the
2
+
Fe ¼ Fe + 2e leaving the surface positively charged. In natu- increase in the number of methylene units in the spacer chain
rally aerated neutral solutions, the released electrons are leads to an increase in the molecule exibility. This hinders the
Fig. 13 HOMO (a) and LUMO (b) distributions in GS2 molecule.
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explained assuming that lengthening the spacer chain
increases the degree of surface coverage and also the average
area occupied by each adsorbed molecule. Hence, the inhibi-
tion efficiency increases. Both phenomena have been observed
in our study for the three gemini surfactants having the same
terminal chain length (dodecyl group) and differing in the
spacer length (2, 6 and 10 methylene groups). Data obtained
from electrochemical and chemical measurements conrm that
GS10 > GS2 > GS6 in inhibition efficiency as well as their critical
concentrations follows the trend: GS10 < GS2 < GS6, i.e.
150 ppm, 200 ppm and 300 ppm, respectively. In other words,
GS10 demonstrates higher efficiency at lower concentration
than GS2 which, in turn, shows also higher efficiency at lower
concentration than GS6. This behavior can be elucidated as
follows (Fig. 12):
(1) For the gemini surfactant of shortest spacer (GS2), the very
short spacer allows the terminal chains to be very close to each
other. So, there is a degree of attraction forces between adjacent
chains in the same molecule and between neighboring molecules
by hydrophobic interaction. This leads to the presence of arrays
of stacked molecules which represent a barrier against corrosive
molecules to penetrate to C-steel surface (Fig. 12(a)).
Fig. 15 HOMO (a) and LUMO (b) distributions in GS10 molecule.
51
adsorption of the gemini surfactant on metal surface and thus
the inhibition efficiency decreases. (ii) The inhibition efficiency
increases as the length of spacer chain is increased. This can be
(2) On the other hand, GS6 has a longer spacer and its
terminal chains are far away from each other so there are weak
Table 10 Quantum chemical parameters calculated for GS2, GS6 and GS10
Molecule
EHOMO (eV)
ELUMO (eV)
DE
I (eV)
A (eV)
c (eV)
h (eV)
m (Debye)
GS2
GS6
GS10
ꢁ8.357
ꢁ8.134
ꢁ8.234
ꢁ1.071
ꢁ0.721
ꢁ1.453
7.286
7.413
6.781
8.357
8.134
8.234
1.071
0.721
1.453
4.714
4.428
4.844
3.643
3.707
3.391
5.946
14.596
30.551
Fig. 16 SEM micrographs and EDX images for: (a) abraded C-steel surface, (b) surface of C-steel immersed in a solution of oilfield water.
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hydrophobic interactions between the terminal chains. In 3.6. Quantum chemical calculations
addition, a specic region on C-steel surface can be covered by
In an attempt to undergo a correlation between computational
chemical calculations and experimental measurements, the
quantum chemical parameters are calculated and discussed. All
optimization calculations were done using VAMP module in
Materials Studio 6.0 soware from Accelrys Inc. The Parametric
Method (PM3), a semi-empirical method was employed to
obtain quantum chemical parameters and to optimize the
a number of GS6 less than GS2. In this case there may be voids
or weak regions through which corrosive species can attack C-
steel surface (Fig. 12(b)).
Unlike GS2 and GS6 whom molecules are predicted to
adsorb on C-steel via vertical orientation, GS10 molecules are
expected to adsorb on C-steel surface via lateral interactions due
to the absence of hydrophobic interactions between terminal
chains. So, both terminal chains in GS10 molecule can extend
over C-steel surface instead of being extended in the solution
52
molecule geometry. As it can be seen in Fig. 13–15, both
HOMO and LUMO regions are focused on imidazolium rings
where in each molecule; HOMO is localized on one imidazo-
lium ring while LUMO is distributed over the other ring. This
indicates that the imidazolium rings are the active parts in
(Fig. 12(c)). Moreover, this mode of interaction allows more
GS10 molecules to overlay on each other forming multilayers.
So, GS10 forms a tough barrier against corrosive species.
A conclusion can be gained from these observations that very
short and very long spacer-gemini surfactants are more efficient
than those of intermediate spacers. This assumption compro-
mises between the previously mentioned contradictory
phenomena concerning the effect of spacer length on the
corrosion inhibition efficiency.
these gemini surfactants. Low values of the gap energy (DE ¼
20
E
LUMO ꢁ EHOMO
) refer to good inhibition efficiencies because
the energy needed to remove an electron from the HOMO of an
inhibitor will be minimized and also it will be easy to donate
electrons for Fe d-orbital. Moreover, ELUMO will be minimum
and thus the inhibitor can gain electrons from lled Fe d-
Fig. 17 SEM micrographs and EDX images for surface of C-steel immersed in a solution of oilfield water inhibited by: (a) 300 ppm GS2, (b)
00 ppm GS6 and (c) 300 ppm GS10.
3
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Table 11 FT-IR stretching absorption bands for gemini surfactants before and after adsorption
Aromatic
C–H
Aliphatic
C–H
Combination
N–H
Aromatic
C]C or C]N
C–Br
or g-Fe O
2 3
59,60
Assignment
N–H
ꢁ1
Absorption bands (cm
)
GS2
Before
Aer
Before
Aer
Before
Aer
3417
3305
3416
3404
3419
3383
3039
—
3073
—
3070
—
2922–2852
2923–2872
2924–2854
2924–2854
2923–2853
2923–2853
2042
—
2062
—
2055
—
1563
1628
1625
1619
1623
1606
636
560
635
590
635
600
GS6
GS10
53
54
orbital or from the lled Fe 4s orbital. Table 10 reveals that indicating the accumulation of corrosion products (salts and
GS10 < GS2 < GS6 in DE giving a theoretical prediction that GS10 oxides) on C-steel surface. These features indicate that C-steel
>
GS2 > GS6 in agreement with the practical results. In litera- surface was highly corroded in oileld water free from inhibi-
ture, there is no regular correlation between the inhibition tors. In contrast, Fig. 17 displays that there are fewer damages
20
efficiency of a corrosion inhibitor and its dipole moment (m).
on C-steel surface in oileld water inhibited by gemini surfac-
If Fe and an inhibitor molecule are brought together, elec- tants following the order: GS10 > GS2 > GS6 in surface protec-
trons will ow from the less electronegative entity to the more tion. Surface enhancement conrms the inhibitive and
electronegative one until the values of the chemical potential protective action of these gemini surfactants for C-steel in oil-
31
become equal. The parameters, electronegativity (c) and global eld water. The corresponding EDX spectra show that there is
hardness (h), were calculated for the prepared gemini surfac- a reduction in the amount of corrosion products where the
tants. These parameters are related to the electron affinity (A) peaks corresponding to salts and oxides formed due to corro-
I þ A
I ꢁ A
sion process are diminished. The reduction in the amount of
corrosion products conrms the anti-corrosion effect of these
and ionization potential (I), where: c ¼
and A are related, in turn, to E
and h ¼
: I
2
2
and ELUMO as: I ¼ ꢁE
HOMO
HOMO gemini surfactants for C-steel in oileld water.
55
and A ¼ ꢁELUMO. Table 10 indicates that GS10 < GS2 < GS6 in
the ELUMO whereas the trend is reversed in the case of the
electronegativity of these compounds (c). Thus, the more elec-
tronegative the molecule, the better its interaction with Fe
surface. These observations indicate that these compounds may
act as potential inhibitors for Fe corrosion via electron transfer
from the metal surface to inhibitor where the transferred elec-
trons are hosted in the antibonding molecular orbitals
3.7.2.
FT-IR. FT-IR is a powerful technique that is always
used for determining the type of bonding of organic inhibitors
57
adsorbed on the metal surface. Compared to those of pure
gemini surfactants, FT-IR absorption bands for the corrosion
products scratched from C-steel surface immersed in oileld
water containing gemini surfactants are shied from their
positions and some bands disappeared (Table 11). These results
strongly support the presence of interaction between the
molecules of these gemini surfactants and the metal surface
56
(
LUMOs) and the measured inhibition efficiency follows the
order GS10 > GS2 > GS6.
58
conrming the occurrence of adsorption process.
3
.7. Surface analysis
4. Conclusions
3.7.1. SEM and EDX. SEM analysis is performed for C-steel
coupons immersed in blank and inhibited solutions of oileld This study evaluates three novel gemini surfactants as inhibi-
water and their SEM micrographs were recorded with a magni- tors for the corrosion of C-steel in oileld water. The main

cation power (5000ꢃ) in order to observe the changes occurred conclusions are as follows:
during corrosion process in the absence and presence of gemini (1) Weight loss method, polarization and EIS measurements
surfactants. Fig. 16(a) shows the SEM micrograph of abraded C- have showed that the synthesized gemini surfactants (GS2, GS6
steel surface where the slight scratches occurring by emery and GS10) are good inhibitors for the corrosion of C-steel in
papers are clearly visible on the surface. The corresponding EDX oileld water and the inhibition efficiency increases with the
spectrum shows that the elements constituting carbon steel inhibitor concentration up to a critical value above which the
sample (Fe, Mn, C and P) appears on EDX spectrum of the inhibition efficiency starts to decrease.
abraded sample in addition to the appearance of oxygen related
(2) The maximum inhibition efficiency values obtained from
to the air-formed oxide lm. Fig. 16(b) shows that C-steel weight loss method for GS2, GS6 and GS10 are 67.64% at
coupon immersed in blank solution was highly damaged and 200 ppm, 62.30% at 300 ppm and 85.21% at 150 ppm,
its surface is full of roughness and cavities. These features respectively.
indicate that C-steel surface was highly corroded in absence of
(3) EIS spectra of C-steel in oileld water in absence and
inhibitors. The corresponding EDX spectrum displays the peaks presence of any of the tested inhibitors show a two-time
of (Fe, Ca, Mg, Cl, S and O) special for the constituents of oileld constant behavior and displays the features of Warburg
2
+
2+
ꢁ
2ꢁ
water (e.g. Ca , Mg , Cl and SO
4
) (Table 2) and iron oxides impedance.
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(4) The synthesized gemini compounds act as mixed-type 18 M. Deyab, M. Osman, A. Elkholy and F. El-Taib Heakal, RSC
corrosion inhibitors, retarding both anodic metal dissolution
and cathodic reactions.
Adv., 2017, 7, 45241–45251.
19 M. Deyab, K. Eddahaoui, R. Essehli, T. Rhad,
S. Benmokhtar and G. Mele, Desalination, 2016, 383, 38–45.
(5) The decrease in corrosion rate of C-steel as a function of
each inhibitor concentration (till its critical value) indicates that 20 H. M. Abd El-Lateef, M. A. Abo-Riya and A. H. Tantawy,
its molecules adsorb on C-steel surface. Corros. Sci., 2016, 108, 94–110.
6) Adsorption of molecules of each gemini surfactant is 21 J. M. Zhao, H. B. Duan and R. J. Jiang, Corros. Sci., 2015, 91,
(
described according to Langmuir isotherm. Both physisorption
108–119.
and chemisorption processes are present but the former is 22 F. El-Taib Heakal, A. S. Fouda and M. S. Radwan, Mater.
predominant. Chem. Phys., 2011, 125, 26–36.
7) Thermodynamic parameters calculated from polarization 23 M. A. Amin, S. S. A. El-Rehim, E. El-Sherbini and
measurements indicate that the presence of these inhibitors R. S. Bayoumi, Electrochim. Acta, 2007, 52, 3588–3600.
increases the activation energy and these compounds are 24 M. A. Deyab and S. S. A. El-Rehim, J. Taiwan Inst. Chem. Eng.,
(
spontaneously adsorbed on C-steel surface mainly via phys-
isorption mechanism.
2014, 45, 1065–1072.
25 F. Ivu ˇs i ´c , O. Lahodny-Sarc, H. O. Curkovic and V. Alar,
Corros. Sci., 2015, 98, 88–97.
ˇ
´
´
(8) Surface analyses (SEM, EDX and FT-IR) conrm the
adsorption of these inhibitors on C-steel surface.
26 Q. Deng, H.-W. Shi, N.-N. Ding, B.-Q. Chen, X.-P. He, G. Liu,
Y. Tang, Y.-T. Long and G.-R. Chen, Corros. Sci., 2012, 57,
2
20–227.
7 F. El-Taib Heakal and S. Haruyama, Corros. Sci., 1980, 20,
87–898.
Conflicts of interest
2
2
2
8
There are no conicts to declare.
8 A. El Bribri, M. Tabyaoui, B. Tabyaoui, H. El Attari and
F. Bentiss, Mater. Chem. Phys., 2013, 141, 240–247.
9 A. M. Awad, O. S. Shehata and F. El-Taib Heakal, Appl. Surf.
Sci., 2015, 359, 939–947.
References
1
2
M. Deyab and S. Keera, Egypt. J. Pet., 2012, 21, 31–36.
30 A. E. Elkholy, M.Sc. thesis, Cairo University, 2017.
M. A. Migahed, M. M. Attya, S. M. Rashwan, M. Abd El-Raouf 31 A. Singh, Y. Lin, E. E. Ebenso, W. Liu, J. Pan and B. Huang, J.
and A. M. Al-Sabagh, Egypt. J. Pet., 2013, 22, 149–160.
M. A. Deyab, Desalination, 2016, 384, 60–67.
P. Boschee, Soc. Petrol. Eng. J., 2012, 1, 22–26.
M. A. M. Deyab, J. Surfactants Deterg., 2015, 18, 405–411.
D. Lopez, S. Simison and S. De Sanchez, Corros. Sci., 2005, 47,
Ind. Eng. Chem., 2015, 24, 219–228.
32 H. Bentrah, Y. Rahali and A. Chala, Corros. Sci., 2014, 82,
426–431.
33 Q. Qu, Y. He, L. Wang, H. Xu, L. Li, Y. Chen and Z. Ding,
Corros. Sci., 2015, 91, 321–329.
3
4
5
6
7
35–755.
34 S. Banerjee, V. Srivastava and M. Singh, Corros. Sci., 2012, 59,
35–41.
35 M. Lebrini, F. Robert, H. Vezin and C. Roos, Corros. Sci.,
2010, 52, 3367–3376.
7
M. Bobina, A. Kellenberger, J.-P. Millet, C. Muntean and
N. Vaszilcsin, Corros. Sci., 2013, 69, 389–395.
M. Deyab, RSC Adv., 2015, 5, 41365–41371.
8
9
M. Deyab, J. Taiwan Inst. Chem. Eng., 2016, 60, 369–375.
36 G. Mu, T. Zhao, M. Liu and T. Gu, Corrosion, 1996, 52, 853–
856.
1
1
1
0 M. Prabakaran, S.-H. Kim, V. Hemapriya, M. Gopiraman,
I. S. Kim and I.-M. Chung, RSC Adv., 2016, 6, 57144–57153. 37 X. Jiang, Y. Zheng and W. Ke, Corros. Sci., 2005, 47, 2636–
1 M. V. Fiori-Bimbi, P. E. Alvarez, H. Vaca and C. A. Gervasi,
Corros. Sci., 2015, 92, 192–199.
2658.
38 D. K. Yadav, M. Quraishi and B. Maiti, Corros. Sci., 2012, 55,
254–266.
2 L. Fragoza-Mar, O. Olivares-Xometl, M. A. Dom ´ı nguez-
Aguilar, E. A. Flores, P. Arellanes-Lozada and F. Jim ´e nez- 39 G. Karthik and M. Sundaravadivelu, Egypt. J. Pet., 2016, 25,
Cruz, Corros. Sci., 2012, 61, 171–184.
183–191.
3 P. Brown, T. Alan Hatton and J. Eastoe, Curr. Opin. Colloid 40 A. Satapathy, G. Gunasekaran, S. Sahoo, K. Amit and
Interface Sci., 2015, 20, 140–150. P. Rodrigues, Corros. Sci., 2009, 51, 2848–2856.
4 M. A. Amin, M. A. Ahmed, H. A. Arida, F. Kandemirli, 41 S. K. Shukla and M. Quraishi, J. Appl. Electrochem., 2009, 39,
1
1
M. Saracoglu, T. Arslan and M. A. Basaran, Corros. Sci.,
011, 53, 1895–1909.
5 F. El-Taib Heakal and A. E. Elkholy, J. Mol. Liq., 2017, 230,
95–407.
6 R. Zana and J. Xia, Gemini surfactants: synthesis, interfacial
1517–1523.
2
42 S. M. Tawk and M. F. Zaky, Res. Chem. Intermed., 2015, 41,
8747–8772.
43 A. M. Al-Sabagh, N. G. Kandile, N. M. Nasser, M. R. Mishrif
and A. E. El-Tabey, Egypt. J. Pet., 2013, 22, 351–365.
1
1
3
and solution-phase behavior, and applications, Marcel 44 M. Deyab, R. Essehli and B. El Bali, RSC Adv., 2015, 5, 48868–
Dekker, New York, 2003. 48874.
7 F. El-Taib Heakal, M. M. Osman, M. A. Deyab and 45 M. A. Migahed, M. M. Shaban, A. A. Fadda, T. A. Ali and
A. E. Elkholy, Z. Phys. Chem., 2017, 231, DOI: 10.1515/zpch- N. A. Negm, RSC Adv., 2015, 5, 104480–104492.
017-0949.
1
2
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 47335–47352 | 47351

View Article Online
RSC Advances
Paper
46 N. A. Odewunmi, S. A. Umoren, Z. M. Gasem, S. A. Ganiyu 53 E. Oguzie, C. Enenebeaku, C. Akalezi, S. Okoro, A. Ayuk and
and Q. Muhammad, J. Taiwan Inst. Chem. Eng., 2015, 51,
77–185.
7 J. C. da Rocha, J. A. d. C. P. Gomes and E. D'Elia, Corros. Sci.,
010, 52, 2341–2348.
8 M. Hegazy, M. Abdallah and H. Ahmed, Corros. Sci., 2010, 52,
897–2904.
9 D. Dwivedi, K. Lepkov ´a and T. Becker, RSC Adv., 2017, 7,
580–4610.
0 D. Ase, M. Arami and N. M. Mahmoodi, Corros. Sci., 2010,
2, 794–800.
1 W. Ansari, J. Aslam and U. Siddiqui, J. Mol. Liq., 2012, 174, 5–
0.
E. Ejike, J. Colloid Interface Sci., 2010, 349, 283–292.
54 F. El-Taib Heakal, A. Fouda and S. Zahran, Int. J. Electrochem.
Sci., 2015, 10, 1595–1615.
55 F. El-Taib Heakal, S. A. Rizk and A. E. Elkholy, J. Mol. Struct.,
2017, DOI: 10.1016/j.molstruc.2017.09.079.
56 F. El-Taib Heakal, S. K. Attia, S. A. Rizk, M. A. Abou Essa and
A. E. Elkholy, J. Mol. Struct., 2017, 1147, 714–724.
57 X. Li, S. Deng, H. Fu and T. Li, Electrochim. Acta, 2009, 54,
4089–4098.
58 T. Ramde, S. Rossi and C. Zanella, Appl. Surf. Sci., 2014, 307,
209–216.
1
4
4
4
5
5
5
2
2
4
5
1
59 B. Stuart, Infrared spectroscopy, Wiley Online Library, 2005.
2 A. Y. Musa, A. A. H. Kadhum, A. B. Mohamad and 60 L. Chauhan and G. Gunasekaran, Corros. Sci., 2007, 49,
M. S. Takriff, Mater. Chem. Phys., 2011, 129, 660–665. 1143–1161.
47352 | RSC Adv., 2017, 7, 47335–47352
This journal is © The Royal Society of Chemistry 2017