The inhibition performance of hydroxy lauric imidazoline for mild steel in chloride solution saturated with CO2

Article abstract of DOI:10.1134/S10704272160020221

In the paper, a novel hydroxy lauric imidazoline (HL-IM) was synthesized using lauric acid and ethylene diamine as raw materials. Methanol reaction method was introduced to prepare the hydroxy lauric imidazoline (HL-IM). According to the results of experiments, the optimum synthesis conditions of methanol reaction was determined through orthogonal experiment, which were: methyl laurate: ethylene diamine = 1: 1, sodium methoxide (0.75 wt %), reaction temperature 100°C, reaction time 2 h. The inhibition efficiency of HL-IM inhibitor was investigated in the condition of 5 wt % NaCl solutions saturated with CO₂ at 333.15 K for 72 h. With 150 mg L^–1 inhibitor dosage, the efficiency of inhibition reached 90.17% by weight loss method. Through film-forming property, foaming characteristic, and emulsification tendency test, it w a s shown that HL-IM had good water-solubility, a smaller emulsification tendency in 5 wt % NaCl solution, and a little foaming performance. Meanwhile, referring to the polarization curves tests, the synergistic effect of HL-IM with the potassium iodide, methylbutynol, and cetyltrimethyl ammonium bromide was studied.

Full text of DOI:10.1134/S10704272160020221

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2016, Vol. 89, No. 2, pp. 304−314. © Pleiades Publishing, Ltd., 2016.
VARIOUS TECHNOLOGICAL
PROCESSES
The Inhibition Performance of Hydroxy Lauric Imidazoline
for Mild Steel in Chloride Solution Saturated with CO21
a
*a,b
*a
b
b
b
Lan Ma , Yi He , PinYa Luo , Yingqing Zhan , RanRan Yang , and Yanqiu Zhou
a
State Key Lab of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum
University, 8 Xindu Avenue, Chengdu, Sichuan 610500, P R of China
School of Chemistry and Chemical Engineering, Southwest Petroleum University, 8 Xindu
b
Avenue, Chengdu, Sichuan 610500, P R of China
*
e-mail: heyi@swpu.edu.cn, luopy@swpu.edu.cn
Received February 29, 2016
Abstract—In the paper, a novel hydroxy lauric imidazoline (HL-IM) was synthesized using lauric acid and eth-
ylene diamine as raw materials. Methanol reaction method was introduced to prepare the hydroxy lauric
imidazoline (HL-IM). According to the results of experiments, the optimum synthesis conditions of methanol
reaction was determined through orthogonal experiment, which were: methyl laurate : ethylene diamine = 1 :
1, sodium methoxide (0.75 wt %), reaction temperature 100°C, reaction time 2 h. The inhibition efficiency
of HL-IM inhibitor was investigated in the condition of 5 wt % NaCl solutions saturated with CO at 333.15 K
2
–
1
for 72 h. With 150 mg L inhibitor dosage, the efficiency of inhibition reached 90.17% by weight loss method.
Through film-forming property, foaming characteristic, and emulsification tendency test, it w a s shown that
HL-IM had good water-solubility, a smaller emulsification tendency in 5 wt % NaCl solution, and a little foam-
ing performance. Meanwhile, referring to the polarization curves tests, the synergistic effect of HL-IM with
the potassium iodide, methylbutynol, and cetyltrimethyl ammonium bromide was studied.
DOI: 10.1134/S10704272160020221
INTRODUCTION
compact and regular film on the metal surface. In the
process, both the hydrophilic heads and hydrophobic tails
played a key role in protecting the metal from corrosion
[13].
In recent years, the corrosion in the oil and gas industry
[
1] caused by CO is more serious. It has been found
2
that, at the same pH, carbonic acid is more aggressive
than hydrochloric acid and causes severe problems for
mild steel pipelines. Solution of this problem, using
inhibitors [2, 3] is one of the most practical methods
for protection against corrosion, especially for acidic
media. Imidazoline inhibitors [4, 5], such as FLEK-IK
In the previous studies, there are several methods
for synthesizing the imidazoline inhibitors, for example,
vacuum method, solvent method. But the traditional
ways of synthesis have some shortcomings, such as high
energy consumption, low utilization of raw materials,
low yield and others. Therefore, the development of
new technology for synthesizing imidazoline inhibitor
becomes a trend.
2
01A, amido-imidazoline derivative [6], Heptadecyl-
tailed mono- and bis-imidazolines [7], diethylenetriamine
imidazoline [8] are widely used to inhibit corrosion
Herein, three methods for hydroxy lauric imidazoline
caused by CO . Imidazole derivatives [9–11] have
2
(
HL-IM) synthesizing were discussed, which are low-
imidazole ring, which can strongly absorb onto the metal
surface, especially for iron. Meanwhile, the hydrophobic
tail of imidazoline prevented the hydropohilic head and
metal from contacting with corrosive medium [5, 12].
Therefore, addition of imidazoline inhibitors can form
pressure reaction method, microwave reaction method,
and methanol reaction method. Methanol reaction method
was proposed to synthesize imidazoline inhibitor, which
was featured by low reaction temperature, low energy
consumption, simple equipment, and easilyindustrialized
production.
1
The text was submitted by the authors in English.
3
04

THE INHIBITION PERFORMANCE OF HYDROXY LAURIC IMIDAZOLINE
305
Scheme 1. Synthesis route of HL-IM by the low-pressure reaction method.
Scheme 2. Synthesis route of HL-IM by the microwave reaction.
So far, there is a lot of research on imidazoline derivatives
14], various modifications on hydrophobic chain were
studied. Due to its long hydrophobic chain, lauric acid
15] as a raw material is used for synthesis imidazoline
inhibitor. Synergistic effect of inhibitor is widely used in
industry, and the different ingredients in synergism have
good inhibition effect. Synergistic effect of inhibitor can
reduce dosage and cost of inhibitors.
ethylenediamine (HE) were chosen to carry out the orthogonal
test. The orthogonal table for acylation stage and cyclization
stage was shown in Tables 1 and 2, respectively.
[
[
Synthesis of hydroxy lauric imidazoline (HL-IM) by
microwave reaction method. Lauric acid and ethylene
diamine in certain ratio was added into a test tube of a
microwave reactor (Discover E-48 Automated microwave
synthesizer). After reaction the sample was kept in the test
tube at room temperature followed by adding ethyl acetate.
The desired product were obtained after the above mixture
was concentrated in a rotary evaporator.
EXPERIMENTAL
Materials
There were three factors affecting a yield of hydroxy
lauric imidazoline: the ratio of lauric acid and hydroxyethyl
ethylenediamine, a reaction time, and a microwave power.
According to experiment, the appropriate conditions of
synthesis were determined.
Sulfuric acid (98 wt %), methanol, lauric acid,
sodium methylate hydroxyethyl ethylenediamine,
sodium methylate, deionized water, sodium chloride.
These reagents were purchased from Chengdu Kelong
Company, China. All reagents were of AR grade and
used as supplied.
Table 1. L9(34) table of orthogonal test for the acylation stage
Factor
Level
Synthesis of Three Types of Hydroxy
Lauric Imidazoline (HL-IM)
LA: HE temperature, pressure, KPa time, h
1
2
3
1 : 1.0
1 : 1.1
1 : 1.2
413.15
433.15
453.15
5
7
1
2
3
Synthesis of hydroxy lauric imidazoline (HL-IM)
by low-pressure reaction method. Acertain molar ratio
of lauric acid and hydroxyethyl ethylenediamine was
added into a 100 mL three-necked flask. The mixture was
heated to 363.15 K. The typical reaction route was shown in
Scheme 1.
10
Table 2. L4(23) table of orthogonal test for the cyclization stage
Factor
temperature, K pressure, KPa
Level
time, h
To optimize the experimental condition, four key factors
such as reaction temperature, reaction pressure, reaction
time, and the ratio of lauric acid (LA) to hydroxyethyl
1
2
483.15
493.15
3
5
3
6
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 89 No. 2 2016

306
LAN MA et al.
Scheme 3. Synthesize route of HL-IM by the methanol reaction method.
Synthesis of hydroxy lauric imidazoline (HL-IM) by the
and finally dried before using. (P110 carbon steel composition
(wt %): 0.26 C, 0.19 Si, 1.37 Mn, 0.004 P, 0.004 S, 0.148 Cr,
0.028 Ni, 0.019 Cu, 0.013 Mo, 0.006 V, 0.062Al, the remainder
is Fe.)
methanol reaction method. Excessive methanol was added
into lauric acid, followed by stirring the mixture until the lauric
acid completely dissolved in methanol. Some sulfuric acid was
added to the above mixture via pressure-equalizing dropping
funnel, then heating mixture by oil bath. After reaction, methyl
laurate was separated using separating funnel. Hydroxyethyl
ethylenediamine and methyl laurate were mixed at a certain
molar ratio, then the blends and sodium methylate (0.75 wt %)
were added to a three-neck flask for reaction under heating.
The hydroxy lauric imidazoline(HL-IM) was obtained after
distilling the excessive methanol by vacuum distillation.
Solutions: The 5 wt % NaCl aggressive solution was
prepared in 500 mL container by adjusting the concentration of
deionized water with NaCl solid, then followed by deoxidizing
via nitrogen bubbles, and bubbling carbon dioxide to guarantee
a saturated solution all the time.
Weight loss measurement. For each concentration of
HL-IM three carbon steel specimens were immersed in
the corrosive medium at 333.15 K for 72 h, in which the
The methyl laurate which was obtained in the esterification
reaction was not soluble in methanol phase. Whether the
reaction was completed was judged by the volume of insoluble
substance. The yield was mainly affected by the reaction time,
reaction temperature, and the ratio of lauric acid methyl ester
and ethylene diamine. L9 (3 ) orthogonal table was shown in
Table 3.
concentration of HL-IM was set to be 0, 50, 100, 150, 200,
–1
2
50 mg L , respectively. Along with a powerful scrub, the
production of corrosion and the adsorbed film were washed
with deionized water, acetone, alcohol, and the deionized water
after immersion for 72 h. The water on the surface of specimen
was sucked by filter paper. At last the specimens were placed
into a dryer before weighing.
4
Content analysis of HL-IM. Content of the reaction
product was determined by extraction-spectrophotometric
method. The blends of imidazolines and acid orange II in acidic
medium was extracted by the chloroform, which can cause the
formation of orange complexes. The maximum absorption peak
of this complex was about 480 nm.The standard work curve
of HL-IM was shown in Fig. 1, the yield of hydroxyl lauric
imidazoline could be calculated from Fig. 1.
Potentiodynamic polarization [16] tests. An electro-
chemical cell with conventional three-electrode compartment
Table 4. Orthogonal experiment of amidation step
Factor
no.
Temperature, Pressure, Time, Yield,
LA: HE
K
KPa
h
%
1
2
1 : 1.0
1 : 1.0
1 : 1.0
1 : 1.1
1 : 1.1
1 : 1.1
1 : 1.2
1 : 1.2
1 : 1.2
53.20
51.97
57.03
5.07
413.15
433.15
453.15
413.15
433.15
453.15
413.15
433.15
453.15
53.70
5.00
1
50.2
57.3
52.1
53.7
53.1
49.1
57.2
56.3
57.6
Characterization and Test
7.00
10.00
5.00
2
3
3
Specimens: P110 carbon steel specimen was used
for weight loss samples, electrodes, SEM and the study
of synergy experiment. The surface of the test steel was
mechanically abraded by emery papers with 200 up to 1200
grit to ensure the same surface roughness, polished and
degreased with acetone, and then washed with distilled water
4
3
2
5
7.00
6
10.00
5.00
1
7
2
8
7.00
3
Table 3. L9(34) table of orthogonal test for methanol reaction
9
10.00
51.87
56.20
54.13
1.25
1
Factor
Level
k1
k2
k3
R
53.63
54.53
54.03
0.9
LA: HE
1 : 1.0
1 : 1.1
1 : 1.3
temperature, K
373.15
time, h
55.57
1
2
3
2
4
6
52.93
423.15
473.15
1.75
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 89 No. 2 2016

THE INHIBITION PERFORMANCE OF HYDROXY LAURIC IMIDAZOLINE
was employed to investigate the electrode behavior in the
307
CO saturated corrosive medium under the monitoring of
2
RARSTAT2273 electrochemical workstation. A platinum
sheet and a saturated calomel electrode (SCE) were used
as auxiliary electrode and reference electrode, respectively.
P110 carbon steel samples embedded in epoxy resin with an
2
exposed surface area of 1 cm were used as working electrodes.
The carbon steel working electrodes were ground up to 1200
grit abrasive paper, ethanol-cleaned, rinsed with distilled water,
and dried prior to use. With a stable open circuit potential,
the polarized potential was drifted from cathodic –150 mV
–
1
to anodic +150 mV at the scanning rate of 0.166 mV s .All
the electrochemical tests were conducted at 333.15 K.
Scanning electron microscopy. The steel coupons were
immersed for 48 h in CO saturated 5 wt % NaCl aggressive
2
–1
Fig.1.Standardworkcurveofhydroxyllauricimidazoline(HL-
IM).
solution without/with 150 mg L HL-IM at 333.15 K, washed
by distilled water, dried and submitted for SEM test. The
morphologies of the uninhibited/inhibited P110 steel surface
were investigated by scanning electron microscope (JSM-
gas. A disappearance time (s) and foam maximum height (mm)
of solutions in 3 min were measured and recorded.
7
500F).
Film-forming property. Based on the reaction between
Synergy experimental. In corrosion medium, a large
amount of HL-IM was needed when the HL-IM was used
alone. And efficiency of pitting corrosion inhibiting remained
to be improved. Herein, the synergy effect [17] of HL-IM with
potassium iodide, methyl acetylene alcohol, and cetyltrimethyl
ammonium bromide (CTAB) was studied by electrochemical
analysis.
iron and copper ions, the film formed on the substitution. Less
copper plating on the specimen surface indicates that corrosion
inhibitor has better film-forming property. There were different
concentrations of HL-IM aqueous solution in a 250 mL jar.
The specimen was suspended in jar, which was placed in water
bath and heated for 1 h at 353.15 K. The specimen was put
into a beaker containing a saturated copper sulfate solution and
soaked for 10 s, and then placed into the pH 3 of hydrochloric
acid solution, observing and calculating the area of copper
coating on the specimen surface.
RESULTS AND DISCUSSION
Synthesis of HL-IM Inhibitor
Water-soluble test. 5% sodium chloride solution (90 mL)
and 10 mg HL-IM were added into 100 mL graduated cylinder.
The solution tighted by the stopper followed by shaking the
solution up and down to mix completely, the solution was heated
in water bath at 353.15 K. The aqueous state of solution in the
cylinder was observed after heating for 30 min and 24 h.
Emulsification test. Referring to the oil and gas industry
standard SY/T 5273-2000 “ water corrosion performance
evaluation method oilfield,” the emulsifying tendency of
Synthesis of HL-IM inhibitor by the low pressure
method. 5% sodium chloride solution (90 mL) and 10 mg
HL-IM were added into 100 mL graduated cylinder. After
tighting the stopper followed by shaking the solution up
and down to mix completely, the solution was heated in
water bath at 353.15 K. The aqueous state of solution in the
cylinder was observed after heating for 30 min and 24 h.
–
1
HL-IM was tested. HL-IM solution (50 mL of 1000 mg L )
was added into cylinder A. In addition, 50 mL of 5%
sodium chloride solution was added into cylinder B as blank
comparative experiments. The two graduated cylinders were
heated to 353.15 K in thermostatic water bath for 30 min.
Shaking up and down the cylinders for 200 times, and putting
it into the water bath again after 10 min the situation of
oil-water interface stratification was observed in cylinder A
and the amount of water in the cylinder A after 60 min was
recorded. Then the phenomenon of solutions in cylinders A
and B was compared.
Table 5. Orthogonal experiment of cyclization step
Factor Temperature, Pressure,
Time,
h
Yield,
%
no.
K
KPa
1
483.15
483.15
493.15
493.15
47.95
53.5
3
3
6
47.7
48.2
52
2
5
3
3
6
4
5
3
55
k1
k2
R
49.85
51.6
1.75
51.35
50.1
1.25
Foaming test. Different concentration of HL-IM in water
solutions was added to graduated cylinders with bubbling CO2
5.55
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 89 No. 2 2016

308
LAN MA et al.
(a)
(b)
Fig. 2. Results of single factor experiment. (a) Effect of reaction time on yield of HL-IM; Microwave power is at 150 W, Ratio of
LA : HE) is 1 : 1, (b) effect of ratio of (LA : HE) on yield of HL-IM; Microwave power is 150 W and reaction time is 3 min.
(
Synthesis of HL-IM by the microwave reaction
changes the yield a little. The optimum the microwave
power is 100W. Therefore the best conditions of HL-
IM synthesized by microwave reaction method are:
microwave power is 100 W, ratio of (LA : HE) is 1 : 1,
and reaction time is 3 min. Under these conditions, the
yield of HL-IM by microwave reaction is 76%.
method. 150 W, ratio of LA to HE 1 : 1. An effect of the
ratio of LA to HE on yield of HL-IM was determined.
Microwave power is 150 W and reaction time is 3 min.
As can be seen from Fig. 2a with the growth in the
reaction time the content of hydroxy lauric imidazoline
increases. But the content of hydroxy lauric imidazoline
increases a little after 3 min. During the time between
Synthesis by methanol reaction method. According
to orthogonal experiments and range analysis in Table 7
an order of factors effecting on yield of HL-IM is the
following: the ratio of ML to HE > the reaction time >
the reaction temperature. The yield of experiment no. 1
is the largest in Table 7, so the best conditions of HL-IM
synthesis are: the ratio of ML to HE is 1 : 1, the reaction
temperature is 373.15 K, the reaction time is 2 h. Under
these conditions the yield of HL-IM is up to 79.5%.
3
to 5 min the content of hydroxy lauric acid (HL-IM)
increases only by 0.5%. The above data indicate that the
reaction could reach equilibrium after 3 min. Prolonging
the reaction time had little influence on the content of
the crude product. So reaction time of 3 min is suitable.
The effect of the ratio of LA to HE on the yield of
HL-IM at certain microwave power and reaction time
was shown in Fig. 2b. With the growth of the ratio
of LA to HE, the content of HL-IM increases. As
the ratio of (LA : HE) reached 1 : 1, the content of
HL-IM increases a little. Considering the cost of raw
materials, LA : HE = 1 : 1 is the appropriate ratio. In
microwave reaction, microwave power directly affects
the temperature of the reaction system and the pressure,
thus further affecting on the yield of HL-IM. According
to the results of Table 6, with the increase of microwave
power, yield of HL-IM rises. It can be concluded that the
yield reached 76% as the microwave power rises up to
Table 7. Orthogonal experiment of the methanol reaction
method
Factor
ML : HE Temperature, K Time, h Yield, %
no.
1
2
1 : 1.0
1 : 1.0
1 : 1.0
1 : 1.1
1 : 1.1
1 : 1.1
1 : 1.3
1 : 1.3
1 : 1.3
78.73
74.77
77.73
3.96
373.15
423.15
473.15
423.15
473.15
373.15
473.15
373.15
423.15
78.60
2
79.5
78.2
78.5
72.8
72.4
79.1
78.5
77.2
77.5
4
3
6
4
6
4
5
6
2
1
00 W. But continuous increasing of microwave power
7
4
8
6
Table 6. Effect of microwave power on yield
9
2
Microwave power, W
Yield, %
k1
k2
k3
R
78.70
76.37
76.17
2.53
5
0
65
76
77
76.17
1
1
00
50
76.47
2.43
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 89 No. 2 2016

THE INHIBITION PERFORMANCE OF HYDROXY LAURIC IMIDAZOLINE
309
Among three methods the maximum yield of HL-
IM is achieved by the method of methanol reaction.
The methanol reaction process is characterized by low
reaction temperature, low energy consumption, simple
equipment, and easily industrialized production.
FTIR Spectrum of HL-IM. The following absorption
bands at 1294.26 (CH symmetric bending), 1462.74 (CH
3
2
asymmetric bending), 2857.02 (CH symmetric stretching),
−
1
and 2915.85 cm (CH asymmetric stretching) were
shown in FTIR spectrum of the HL-IM inhibitor (Fig. 3).
–
1
And the characteristic peak appearing at 1609.30 cm
is obviously a C=N stretching peak, providing evidence
for the presence of imidazole ring. This fact illustrates
the synthesis of HL-IM inhibitor is successful. The data
of FTIR spectrum confirm that the expected functional
groups in the synthesized HL-IM inhibitor.
Fig. 3. FTIR spectrum of HL-IM inhibitor.
Weight loss method. Through weight loss experiment,
the values of average corrosion rate (r 0c orr) in different HL-
IM concentrations are showed in Fig. 1, which indicates
the HL-IM controls the corrosion rate of specimens. The
inhibition efficiencies are calculated [18] by Eqs. (1)
and (2).
through the surplus charges of organic molecule reacting
with the blank orbit of Fe to form the coordination bond.
Thus, an adsorption film is formed on the surface of
steel, which protects the steel from corrosion, leading to
isolation of the contact between the corrosive medium
and steel.
Table 9 shows the effect of temperature on the
performance of corrosion inhibitors. The dosage of
HL-IM in corrosive medium is 150 mg L . The range
4
8
.76 × 10 Δm
rcorr = –––––––––––,
stρ
(1)
–1
of experimental temperature is 298.15–363.15 K. With
increasing the temperature, the efficiency of HL-IM
inhibitor declines. Because the adsorption of HL-IM
inhibitors on the specimen surface active sites is an
exothermic reaction. When the temperature rises up,
the adsorption rate of inhibitor declines, and desorption
process accelerates corrosion of metal surface, increasing
the difficulty of filming on the P110 steel. But when the
temperature rises, the efficiency of HL-IM changes a
little, which illustrates that HL-IM inhibitor exhibits good
thermal stability.
whereinΔm is the mass loss of P110 steel coupons before
and after immersing in aggressive solutions. Here s is the
area of steel, t is time of evaluation, ρ is density of P110
steel, rcorr is the corrosion rate of steel coupons.
0
r
– r
corr
corr
η = –––––––––– × 100,
(2)
0
r
corr
where η is the inhibition efficiency, %; r 0c orr and rcorr are
the corrosion rate without and with HL-IM, respectively.
Table 8 shows that the corrosion rate decreases with
the increasing concentrations of HL-IM. As the dosage
of HL-IM is below 150 ppm the corrosion rate decreases
rapidly. Meanwhile, the inhibition efficiency increases
with the increasing concentrations of HL-IM. When
Table 8. Inhibition efficiencies of concentrations
Concentrations of
HL-IM, mg L
Corrosion
rate, mm a
η, %
θ
–
1
–1
–1
concentration of HL-IM is 150 mg L , and inhibition
efficiency reaches 90.17%. When the concentration is
0
0.175
–
–
–1
more than 150 mg L , the inhibition efficiency of HL-IM
changes a little. The increasing dosage of HL-IM inhibitor
accelerates the efficient and extensive adsorption of HL-
IM on the metal surface. Namely, N and imidazole ring as
two adsorption centre firstly adsorb onto the metal surface
5
0
0.0524
0.0272
0.0172
70.05
84.46
90.17
0.7005
0.8446
0.9017
1
1
00
50
2
2
00
50
0.0168
0.0165
90.40
90.50
0.9040
0.9050
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 89 No. 2 2016

310
LAN MA et al.
Table 9. Inhibition efficiencies of HL-IM at different
Table 10. Electrochemical parameters of Tafel polarization
temperature
Icorr
A cm
,
C, mg L–1 Ecorr, V
βa
βc
η, %
–2
Temperature , K
η, %
0
–0.74
–0.73
–0.73
–0.70
15.85
5.01
1.82
0.78
6.11
7.95
0.9
–
2
98.15
93.90
5
0
1.77
68.39
88.52
95.09
3
3
3
13.15
33.15
63.15
91.32
90.17
84.22
1
00
13.45 1.82
20.67 2.01
150
Potentiodynamic Polarization Test
current gradually decreases with the increasing HL-IM
dosage. It was easily found that Tafel slope of anodic
The results of the potentiodynamic polarization test
were shown in Fig. 4, which reveals that the potential is
significantly shifted to the positive direction by adding
HL-IM inhibitor. Furthermore, in the presence of different
HL-IM dosages, the more remarkable positive shifts
show that the HL-IM inhibitor inhibits corrosion of steel
polarization curves (β ) increases significantly, and Tafel
a
slope of cathode polarization curves (β ) changes a little
c
[20–23]. The results show that HL-IM inhibits both the
anodic reaction and cathode reaction. It suggests that
HL-IM acts as a mixed-type inhibitor.
in CO saturated 5 wt % NaCl solution mainly through
Scanning Electron Microscopy (SEM)
2
controlling the reaction of anode, although slight shifts are
observed in the curves of both anode and cathode [19].
SEM images of the P110 steel specimen surface after
immersion in CO saturated 5 wt % NaCl aggressive
2
Tafel polarization curves for P110 steel in CO2
saturated 5 wt % NaCl aggressive solution with dif-
ferent concentrations of HL-IM are depicted in Fig. 4.
The corrosion current (Icorr), corrosion potential (Ecorr),
the cathodic (β ) and anodic (β ) slopes are tabulated in
solution for 48 h at 333.15 K are shown in Fig. 5. The
micrograph (a), (c) reveals that the surface is strongly
damaged in the aggressive solution. Figures 5b, 5d
show the SEM images of P110 steel surface inhibited by
c
a
–
1
1
50 mg L of HL-IM, the mild steel surface is severely
Table 10. The current density of the P110 steel electrode
–
2
damaged. It indicates that the P110 steel coupons are less
corroded by 5 wt % NaCl aggressive solution saturated
decreases from 15.85 to 0.79 A·cm in the concentra-
tion range. Meanwhile the inhibition efficiency rises up
to 95.09%. The data of Table 9 show that the corrosion
with CO due to the protective effect of HL-IM inhibi-
2
tor. This is because of the formation of a protective film
of HL-IM on the mild steel surface imparts a smoother
surface to the substrate.
The result in Fig. 6 shows that surface area of the
copper layer is gradually decreased. When the inhibitor
3
2
1
–
1
concentration is 150 mg L the surface area of the speci-
men is about 1/3 of the copper layer. As the dosage of
–
1
corrosion inhibitor is more than 150 mg L , the surface
areas of copper layer on specimen increases a little. This
result is consistent with the results measured by the weight
loss experiment.
Water-Soluble Test
The HL-IM aqueous solution was homogeneous and
non-transparent after placing for 30 min at 353.15 K, and
remained homogeneous and non-transparent in 24 h at
353.15 K. The result showed that HL-IM was of good
water-solubility.
Fig. 4. Tafel polarization curves for P110 carbon steel
electrodes in the absence of HL-IM and with various
–1
concentrations of HL-IM, mg L : (1) blanc, (2) 50, (3) 100,
4) 150, (5) 200.
(
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 89 No. 2 2016

THE INHIBITION PERFORMANCE OF HYDROXY LAURIC IMIDAZOLINE
311
1
0 μm
10 μm
1
μm
1 μm
Fig. 5. SEM micrographs of P110 steel surface (a, c) uninhibited and (b, d) inhibited by HL-IM.
in HL-IM inhibitor’ dosage, the foam maximum height
Emulsification Test
(mm) and disappearance time (s) both increased.
The oil–water interface in cylinder A was clear after
0 min, and the amount of water was more than the
amount of water in cylinder B. We could know that HL-
IM had a smaller emulsification tendency in 5 wt % NaCl
solution from above results.
1
Synergy Experiment
According to the Fig. 8, the mixture of HL-IM and
potassium iodide [24] makes the corrosion potential move
to anode. Slope of cathodic polarization curves increases
sharply, however the slope of anodic polarization curves
changes a little. This illustrates that mixture of HL-IM
and potassium iodide has good inhibition, which mainly
Foaming Test
Figure 7 revealed that HL-IM had a little foaming
performance, but not obviously. Along with the increase
Fig. 6. Surface area of specimens for different concentrations
Fig. 7. Foaming performance for different concentrations of
of HL-IM.
HL-IM.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 89 No. 2 2016

312
LAN MA et al.
Fig. 8. Tafel polarization curves of HL-IM (M) with potassium
Fig. 9. Tafel polarization curves of HL-IM (M) with
methylbutynol (Q), mg L : (1) blanc, (2) 50 M + 50 Q,
(3) 50 M + 100 Q, (4) 50 M + 150 Q, (5) 50 M + 200 Q.
–
1
–1
iodide (N), mg L : (1) blanc, (2) 50 M + 50 N, (3) 50 M +
00 N, (4) 50 M + 200 N.
1
inhibits the cathodic process of corrosion. Because of the
absorption property, iodide ions can affect metal/solution
interface layer’s structure and charged properties that
leads to the improvement of the absorbability for HL-IM
inhibitor. When the dosages of HL-IM and potassium
the metal surface, so that the performance of corrosion
inhibitors was strengthened.
Adsorption Isotherm
In order to determine the best fit at 333.15 K for
several adsorption isotherms, Langmuir, Temkin, and
Frumkin isotherms were considered. As depicted in
Fig. 11, straight lines are obtained when C/θ is plotted vs.
C and the linear correlation coefficients of the fitted data
are 0.99802 indicating that HL-IM was easily absorbed
on the P110 surface and therewith protected the steel.
The slope and intercept of HL-IM were 1.02688 and
16.866, respectively. This confirms that the adsorption of
corrosion inhibitor obeys Langmuir adsorption isotherm
expressed as the following Eq. (3) [25]:
–
1
iodide were 50 and 200 mg L , respectively, potassium
iodide already has good synergistic effect on inhibition
at room temperature in CO saturated 5 wt % NaCl
2
aggressive solution.
The mixture of HL-IM and methylbutynol are added
into aggressive solutions. Both the anodic and cathodic
slopes of P110 carbon steel polarization curves increase
a little. Figure 9 reflects that the mixture of HL-IM and
methylbutynol belongs to inhibitors of a mixing type.
When the amounts of HL-IM and methylbutynol are 50
–1
and 200 mg L , individually, the mixture exhibits the
best effect on inhibition of steel.
C
1
i
–
–– = ––– + C ,
(3)
(4)
i
θ
K
ads
Hydroxy lauric imidazoline and cetyltrimethyl
ammonium bromide (CTAB) [24] as complexes are
added into aggressive solution, there is a significant
moving forward of corrosion potential. The corrosion
current gradually decreases with the increasing of
cetyltrimethyl ammonium bromide’s dosage. Slope of
cathodic polarization curve changes a little, while the
slope of anode polarization curve was greatly changed,
indicating that complexes of hydroxy lauric imidazoline
and cetyltrimethyl ammonium bromide inhibit the
anodic process. Therefore, the mixture is anode type
inhibitor. Surfactants may improve the dispersion of
HL-IM inhibitor in water-soluble medium. Surfactants
have a synergistic effect in the adsorbed film forming on
Δm – Δm
0
θ = –––––––,
Δm
0
In the equation, θ is the surface coverage listed in Table
8, which is determined by the weight loss through Eq. (4),
Kads is the adsorption-desorption equilibrium constant,
C is the concentration of inhibitor [26]. The adsorption-
i
desorption equilibrium constant K approaching to
ads
3
3.73×10 for HL-IM was employed to evaluate the
standard Gibbs free energy (ΔG ) of adsorption through
0
ads
Eq. (5) [22]:
ΔG0 = –RTln (55.5Kads),
(5)
ads
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 89 No. 2 2016

THE INHIBITION PERFORMANCE OF HYDROXY LAURIC IMIDAZOLINE
313
2
–
9.5 –8.5 –7.5 –6.5 –5.5 –4.5 –3.5
Fig. 10. Tafel polarization curves of HL-IM (M) with
–1
cetyltrimethyl ammonium bromide (S), mg L : (1) blanc,
2) 50 M + 25 S, (3) 50 M + 50 S, (4) 50 M + 100 S, (5) 50 M +
50 S.
(
1
Fig. 11. Langmuir adsorption plot of HL-IM on P110 steel
surface in CO saturated 5% NaCl solution at 333.15 K.
2
–
1
where R represents the universal gas constant
at 333.15 K for 72 h. With 150 mg L inhibitor dosage,
the inhibition efficiency reaches 90.17% by the weight
loss method. With the increasing dosage of HL-IM, the
inhibition efficiency of HL-IM demonstrates distinct
uptrend. HL-IM inhibitor exhibits good thermal stability.
8.314 J mol–1 K ), T is the temperature (333K) and
–1
(
5
–
1
5.5 is the molar concentration (mol L ) of water in the
0
–1
solution. So, the value of ΔG is –33.89 kJ mol for
ads
HL-IM.
0
The value of ΔG , generally, in the range of 0 to
(3) With the potentiodynamic polarization test, it
suggests that HL-IM acts as a mixed-type inhibitor. In
addition, HL-IM inhibitor has good synergistic effect
with potassium iodide, methylbutynol, and cetyltrimethy
lammonium bromide (CATB).
ads
–1
2
0 kJ mol was corresponding to the physical adsorption
which was introduced by electrostatic interaction between
the charged molecules and the charged metal surface.
While, beyond the value of 40 kJ mol the adsorption
was dominated by the chemical adsorption resulting from
the coordination of corrosion inhibitor with the metal
through both the sharing and transferring of charges to
–
1
REFERENCES
0
1. Dawson, J.L., G. John, and K. Oliver, in Shreir’s Corrosion,
Stott, B.C.G.L.L.R.S., Ed.. Elsevier: Oxford, 2010,
p. 3230–3269.
the metal unoccupied orbit [27]. Here, the value ofΔG
ads
–
1
for HL-IM is –33.89 kJ mol and the adsorption of HL-
IM on P110 steel surface occurs by both physisorption
and chemisorptions.
2
3
4
. Nam, N.D., et al., Corrosion Sci., 2013, vol. 76, pp. 257–
66.
. Nam, N.D., et al., Corrosion Sci., 2014, vol. 80, pp. 128–
38.
2
CONCLUSIONS
1
. Ortega-Toledo, D.M., et al., Corrosion Sci., 2011, vol. 53,
(
1) Through test, methanol reaction method is proved
no. 11, pp. 3780–3787.
to be the best method of HL-IM synthesis. The optimal
synthesis conditions are: methyl laurate : ethylene
diamine = 1: 1, sodium methoxide (0.75 wt %), reaction
temperature is 100°C, reaction time is 2 h. HL-IM
is characterized by good water-solubility, a smaller
emulsification tendency in 5 wt %NaCl solution, and a
little foaming performance, but not obviously.
5. Okafor, P.C., Liu, X., and Zheng, Y.G., Corrosion Sci.,
009, vol. 51, no. 4, pp. 761–768.
2
6. Heydari, M. and Javidi, M., Corrosion Sci., 2012, vol. 61,
pp. 148-155.
7
. Jawich, M.W.S., Oweimreen, G.A., and Ali, G.A.,
Corrosion Sci., 2012, vol. 65, pp. 104–112.
(
2) The inhibition efficiency of HL-IM inhibitor was
8. Jevremovic, I., et al., Corrosion Sci., 2013, vol. 77,
investigated in 5 wt % NaCl solutions saturated with CO2
pp. 265–272.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 89 No. 2 2016

3
14
LAN MA et al.
18. Negm, N.A., et al., Corrosion Sci., 2012, vol. 65, pp. 94–
9
. Zhang, K., et al., Corrosion Sci., 2015, vol. 90, pp. 284–
95.
0. Liu, F., et al., Corrosion Sci., 2015, vol. 93, pp. 293–300.
1. Jevremović, I., et al., Corrosion Sci., 2013, vol. 77,
2
103.
1
19. Liu, F.G., et al., Corrosion Sci., 2009, vol. 51, no. 1,
pp. 102–109.
1
2
0. Obot, I.B., et al., J. Ind. & Eng. Chem., 2015, vol. 21,
pp. 265–272.
pp. 1328–1339.
1
1
2. Finšgar, M. and Jackson, J., Corrosion Sci., 2014, vol. 86,
2
1. Yıldız, R., Corrosion Sci., 2015, vol. 90, pp. 544–553.
2. Hamani, H., et al., Corrosion Sci., 2014, vol. 88, pp. 234–
pp. 17–41.
2
3. Olivares-Xometl, O., et al., Appl. Surface Sci., 2006,
2
45.
vol. 252, no. 6, pp. 2139–2152.
2
2
3. McCafferty, E., Corrosion Sci., 2005, vol. 47, no. 12,
1
4. He, X., et al., Corrosion Sci., 2014, vol. 83, pp. 124–136.
pp. 3202–3215.
1
5. Lu, P., et al., Arc. Biochem. & Biophys., 1997, vol. 337,
4. Arukalam, I.O., Carbohydrate Polymers, 2014, vol. 112,
no. 1, pp. 1–7.
pp. 291–299.
1
1
6. El-Haddad, M.N., Carbohydrate Polymers, 2014, vol. 112,
25. Qian, B., et al., Corrosion Sci., 2013, vol. 75, pp. 184–192.
pp. 595–602.
2
6. Zhang, F., et al., Science, 2010, vol. vol. 52, vol. 9,
7. Jabeera, B., Shibli, S.M.A., and Aniradhan, T.S. Appl.
Surface Sci., 2006, vol. 252, no. 10, pp. 3520–3524.
pp. 3042–3051.
27. Herrag, L., et al., Corrosion Sci., 2012, vol. 61, pp. 1–9.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 89 No. 2 2016