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Carbon Dots as Green Corrosion Inhibitor for Mild Steel in HCl Solution
Article in ChemistrySelect · July 2020
DOI: 10.1002/slct.202000625
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Indian Institute of Technology (ISM) Dhanbad
Defence Institute of Advanced Technology
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z Electro, Physical & Theoretical Chemistry
Carbon Dots as Green Corrosion Inhibitor for Mild Steel in
HCl Solution
Vandana Saraswat and MahendraYadav*[a]
Two carbon dots namely, S, N co-doped (CD1) and N doped
(CD2) were synthesized by solvothermal treatment of pyromelletic acid in presence of thiourea, urea and DETA at 180 °C. The
synthesized carbon dots were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Transmission electron microscopy (TEM) and Raman spectroscopy analysis. The dimension
of synthesized carbon dots were found in the range of 1.63 nm
to 2 nm with significant graphitic carbons. These carbon dots
(CD1 and CD2) were used as green corrosion inhibitor to
mitigate corrosion of mild steel (MS) in 15 % HCl solution using
gravimetric and electrochemical methods. Studied carbon dots,
CD1 and CD2 exhibited inhibition efficiency of 96.40 and
90.00 %, respectively, at 100 ppm concentration and 303 K
temperature. The observed corrosion inhibition occurs due to
adsorption of the carbon dots to the MS surface. Both the
carbon dots follow Langmuir adsorption isotherm model and
show physisorption on the MS surface. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis
was used to study the morphology of the uninhibited and
inhibited surface of the sample. The interaction of the carbon
dots and composition of adsorbed layer on the MS surface was
confirmed using X-ray photoelectron spectroscopy (XPS). The
XPS analysis revealed that heteroatoms present in the structural moiety of the carbon dots efficiently binds on the MS
surface.
1. Introduction
demand towards eco-friendly pickling corrosion inhibitors with
high corrosion inhibition efficiency and low price have come in
the demand.[10,11,12]
Carbon dots (zero dimensional materials) have gain huge
interest in last decade due to their low cost, non-toxicity, easily
available raw materials and easy preparation methods.[13,14]
They have applications in catalysis, cell imaging, sensors,
biomedicine, and optoelectronic devices.[15] Presently carbon
dots found application as green corrosion inhibitor and
displayed promising results. Ye.et al. synthesized three types of
carbon dots N-CDs, first one by taking citric acid carbon dots,
N-carboxysuccinimide and (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride as starting material, second one by
taking ammonium citrate as raw material and third one
prepared by using methacrylic acid and n-butylamine as raw
material by using hydrothermal process and reported that
these carbon dots exhibit corrosion inhibition efficiency of 93.4,
84 and 94 %, respectively, at 200 ppm concentration and 303 K
temperature for MS in 1 M HCl solution.[16–18] Yang et al.
prepared citric acid based ionic liquid functionalized CDs and
examined inhibitive nature on carbon steel in HCl and NaCl
soution, found 92.6 and 83.45 % efficiency respectively at
200 ppm.[19] Cen et al. prepared carbon dots by taking aminosalicylic acid and thiourea as starting material and reported
93 % efficiency on carbon steel in NaCl solution at 50 ppm
concentration.[20] Cui et al. synthesized carbon dots by taking 4aminosalicylic acid as raw material and reported its corrosion
inhibition efficiency of 87.2 % on steel in HCl at 100 ppm
concentration.[21] Wang et al. synthesized N-doped carbon dots
and studied inhibitive nature on copper in H2SO4 solution,
found 89.2 % efficiency at 50 ppm.[22] Ye. et al. synthesized
some N-doped carbon dots (N-CDs) and reported that these
MS is one of the most widely used construction materials for
industrial equipments such as heat exchanger, cooling system,
boilers etc. Due to prolonged usage of these equipments scales
of carbonate and rust accumulates at the exterior surface.[1,2]
For removal of scales and rust these equipments often exposed
to strong acids such as HCl, H2SO4, phosphoric acid and HF
solution. Among these HCl and H2SO4are commonly used.
These acids not only remove the scales efficiently but also
corrode the metallic structure, which leads to huge economic
losses.[3] The application of corrosion inhibitor is one of the
simplest methods to mitigate the corrosion of MS in acidic
environment. Inorganic inhibitors such as molybdates, chromates and phosphates are the initial preferences. In spite of
their good corrosion inhibition efficiency towards metals and
alloys, mostly they are hazardous to the human health and eco
system. Hence as an alternative, the application of organic
corrosion inhibitors is gaining much significance in industrial
sectors. Organic compounds containing N, O, P, S along with
aromatic ring and long alkyl chain in their structural moiety are
reported as efficient corrosion inhibitors for MS in acidic
environment.[4–8] These corrosion inhibitors give good inhibition
efficiency, but some of these are also toxic and not good for
human health as well as environment.[9] In present time people
awareness towards environment has increased and the
[a] V. Saraswat, Dr. MahendraYadav
Department of Chemistry, IIT(ISM) Dhanbad, Jharkhand 826004, India
E-mail: mahendra@iitism.ac.in
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/slct.202000625
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carbon dots act as good corrosion inhibitor for steel in HCl
solution.[23,24] Seeing the good corrosion inhibition property of
carbon dots, in present investigation CD1 and CD2 carbon dots
were synthesized and their corrosion mitigation property was
studied for mild steel (MS) in 15 % HCl solution using,
gravimetric, potentiodynamic and electrochemical impedance
spectroscopy (EIS) methods. TEM, FTIR and Raman spectroscopy was performed to elucidate the structure of the
synthesized carbon dots. Two type of carbon dots, CD1 and
CD2 were taken to study the effect of dopent on corrosion
inhibition efficiency. Surface characterization of uninhibited
andinhibited sample was performed by using SEM, AFM and
XPS analysis.
2.1.2. FTIR
FTIR spectra of CD1 and CD2 were carried out before and after
exposure to corrosive conditions are displayed in Figure 2.It
was observed that in CD1 spectra, stretching frequency of C=N,
C=O, C=S, N H and N=C=S were seen at 1645, 1715, 1110,
3460 and 2070 cm 1 respectively, whereas after corrosion these
peaks were shifted at1630, 1703, 1100, 3400 and 2060 cm 1
respectively. In case of CD2 stretching frequency of C=O, C=N
and N H were seen at 1720, 1630 and 3450 cm 1 respectively
and after corrosion process these peaks were shifted at 1710,
1620 and 3410 cm 1respectively. The outcome reflects the
interaction between MS surface and CD1 and CD2 resulting
adsorption through these functional groups.
2. Results and discussion
2.1. Characterization of CDs
2.1.1. TEM
TEM was done to analyze the structural properties of the
synthesized CD1 and CD2 (Figure 1). These carbon dots show
uniformity. The average range of S, N-CDs and N-CDs are 2 nm
and 1.63 nm, respectively.
2.1.3. Raman spectroscopy
The Raman study was carried out to analyze the different state
of carbon of CD1 and CD2, which represents the two peaks
about 1310, 1631 cm 1and 1301, 1627 cm 1, respectively
associated to the D and G band, respectively, as displayed in
Figure 3.
Figure 1. TEM images of (a) S, N- CDs (b) N- CDs.
Figure 2. FTIR of (a) pure CD1 and corrosion product (b) pure CD2 and corrosion product
ChemistrySelect 2020, 5, 7347 – 7357
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Table 1. -Corrosion parameters for (a) CD1 (b) CD2.
Conc. (ppm)
Blank
CD1
10
25
50
75
100
CD2
10
25
50
75
100
303 K
313 K
323 K
333 K
CR (mmy 1)
θ
η %
CR
(mmy 1)
θ
η%
CR (mmy 1)
θ
η%
CR
(mmy 1)
θ
η%
38.4
13.33
–
0.65
–
65.28
67.3
28.41
–
0.57
–
57.78
110.4
49.37
–
0.55
–
55.28
172.5
85.93
–
0.50
–
50.18
9.98
6.17
3.36
1.38
14.66
0.74
0.83
0.91
0.96
0.61
74.01
83.93
91.25
96.40
61.82
22.13
14.65
9.40
5.11
30.75
0.67
0.78
0.86
0.92
0.54
67.11
78.23
86.03
92.4
54.3
40.72
29.78
21.71
13.46
53.21
0.63
0.73
0.80
0.87
0.51
63.11
73.02
80.33
87.8
51.8
72.26
57.40
43.24
28.29
95.56
0.58
0.66
0.74
0.83
0.44
58.11
66.72
74.93
83.6
44.6
11.78
9.02
6.43
3.84
0.69
0.76
0.83
0.90
69.32
76.51
83.25
90.00
26.16
20.78
14.77
9.42
0.61
0.69
0.78
0.86
61.12
69.12
78.05
86.0
48.11
40.61
30.75
20.64
0.56
0.63
0.72
0.81
56.42
63.21
72.14
81.3
85.69
73.29
57.20
39.67
0.50
0.57
0.66
0.77
50.32
57.51
66.84
77.0
The D band is assigned to sp3 hybridized carbon and G
band is assigned to sp2 hybridized carbon. The ID/IG ratio for
CD1 and CD2 is 1.13 and 1.21, respectively, reflecting
graphitization degree in the synthesized carbon dots.[25]
2.2. Gravimetric measurements
Gravimetric measurement was performed in absence and in
presence of inhibitor at various concentrations and temperatures, obtained results are displayed in Table1.
Table 1, shows that the enhancement in inhibitor concentration, enhanced the inhibition efficiency due to enhancement
in adsorption of the studied carbon dots with enhancement in
concentration. The higher extent of adsorption efficiently
protects the corrosion sites of the MS surface and thereby
suppresses the CR :[26] The observed h % of CD1 and CD2 at
100 ppm was 96.4 and 90.00 %, respectively, at 303 K. With the
increase in temperature, corrosion inhibition efficiency of CD1
and CD2 decreases due to the desorption of CD1 and CD2 from
the MS surface.[27] The inhibition efficiency of CD1 is higher
than CD2 because adsorption through both S, N present in
CD1 is stronger as comparison to N alone[28] in CD1.
2.3. Kinetic and thermodynamic parameters
Arrhenius equation was used to calculate apparent activation
energy Ea.
logCR ¼
Ea
þ logP
2:303 RT
(1)
where P is pre-exponential factor, T is temperature, Ea is the
apparent activation energy, R is the universal constant of gas
and CR is the corrosion rate.
Slope of log CR vs 1/T (Figure 4) was used to evaluate
apparent activation energy and acquired values are given in
Table 2. It can be seen from Table 2 that Ea in presence of
inhibitor is higher than in absence of inhibitor because of the
CD1 and CD2 adsorption on the MS surface.[29]
Table 2. Kinetic parameters for (a) CD1 (b) CD2
Concentration(ppm)
Ea( kJmol 1)
ΔH (kJ/mol)
ΔS (Jmol 1K 1)
CD1
42.04
51.65
55.06
62.20
71.53
84.47
51.88
55.18
58.49
61.29
65.50
39.38
49.01
52.44
59.56
68.89
81.83
49.24
52.53
55.85
58.64
62.86
84.68
61.55
52.63
33.14
7.27
28.47
60.06
50.88
42.17
35.89
26.24
CD2
Figure 3. Raman spectra of CD1 and CD2
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Blank
10
25
50
75
100
10
25
50
75
100
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Figure 4. Arrhenius graphs for: (a) CD1 (b) CD2
Transition equation was used for evaluating entropy of
activation (DS ) and enthalpy of activation (ΔH ).
*
CR ¼
RT DS�
eRe
NH
*
DH�
RT
(2)
ΔS and ΔH values were evaluated from slope and
intercept of log (CR/T) vs 1/T ( Figure 5) plots and acquired
values are displayed in Table 2. Table 2 reflects that
enhancement in concentration of CD1 and CD2, results in
enhancement of ΔH reflecting that greater extent of energy
needed for MS dissolution reaction. Positive sign of enthalpy
indicates that nature of MS dissolution is endothermic. It can
also be inferred that the enhancement in ΔS reflecting
enhancement in disorderness during the corrosion process.
*
*
*
q
1
q
¼ K ads C
(3)
where C is concentration and K ads is equilibrium constant.
Figure 6, represents the relation between C and C/ q. By
computing, the correlation coefficient (R2) and slope values
were found closer to 1, suggested a perfect linear correlation
and Langmuir adsorption isotherm is obeyed. Higher K ads values
for both inhibitors suggested strong adsorption of these
inhibitors on MS surface. From Table 3 it is clear that CD1 has
higher K ads values than CD2, indicates that CD1 shows better
adsorption tendency than CD2. The values of free energy of
adsorption ðDG0ads Þ was calculated by equation
*
2.4. Adsorption isotherm
The Langnuir adsorption isotherm is represented by the
following equation
DG0ads ¼
RTlnð55:5K ads Þ
(4)
Calculated DG0ads values are shown in Table 3: DG0ads values
gives the information about the nature of adsorption of
inhibitors. The obtained value of DG0ads lies within the range of
22.20 to
22.93 kJ mol 1 for CD1 and
22.00 to
1
22.76 kJ mol
for CD2. Hence it can be inferred that
Figure 5. Transition-state plots for (a) CD1 (b) CD2
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Figure 6. Langmuir plots for (a) CD1 (b) CD2
Table 3. Adsorption parameters of (a) CD1 (b) CD2.
Inhibitor
Temperature (K)
K ads (L/g)
CD1
303
313
323
333
303
313
323
333
121.43
100.8
86.32
71.4
112.18
90.66
78.43
67.24
CD2
DGads (kJ mol 1)
22.20
22.45
22.75
22.93
22.00
22.17
22.49
22.76
Slope
R2
DHads
(kJ mol 1)
.9746
1.001
1.059
1.106
1.192
1.054
1.082
1.150
0.9947
0.9919
0.9882
0.9809
0.9618
0.9910
0.9822
0.9722
14.66
14.08
adsorption process of CD1 and CD2 on the mild steel surface
followed physisorption.[30]
For the confirmation of nature of adsorption (physical,
chemical and mixed adsorption), enthalpy of adsorption (~Hads)
values were calculated by following thermodynamic equation:
DGads ¼ DHads
TDSads
(5)
The intercept of the plot of DG0ads vs ~T (Figure 7) gives the
value of ~Hads as displayed in Table 3. The negative values of
~Hads for both inhibitors (Table 3) demonstrated that inhibitor
molecules adsorption on MS surface is exothermic in nature.
~Hadsvalues less negative than
40 kJ/mol indicates physical adsorption and nearly 100 kJ/mol indicates chemical
adsorption.[31] In present work, ~Hads values for CD1 and CD2
are 14.66 and 14.08 kJ/mol, respectively, confirmed physical
adsorption
2.5. Electochemical measurement
Fig. 9 shows Nyquist plots of CD1 and CD2. The Nyquist plots
show single capacitive loop, which indicates the single charge
transfer process with single time constant throughout the
dissolution of MS. The depressed capacitive loop of Nyquist
plots are due to roughness and non-uniformity[32] of the MS
surface. The increase in the loops diameter with increase in
concentration suggested increase in polarization resistance (Rp)
ChemistrySelect 2020, 5, 7347 – 7357
Figure 7. ~Gads vs T plot for CD1 and CD2
due to increase in surface coverage of MS by increased
adsorption of CD1 and CD2. The nature of capacitive loop is
almost remain same with and without inhibitor suggested that
mechanism of corrosion is same with and without inhibitor.[33]
Resulted Nquist plots were fitted in equivalent circuit with one
time constant as represented in Figure 8. In this circuit RP and
CPE are connected in parallel and both are placed in series to
the solution resistance (RS).
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Figure 8. Equivalent circuit of CPE
A constant phase element (CPE) is used instead of Cdlto get
the good fitting. The values of Cdl was calculated by the
equation.
1
Cdl ¼ ðY 0 R1P n Þn
(6)
where, n and Y0 are CPE component and CPE constant
respectively.
The values Cdl, RP, Y0, n, RS obtained from fitting the Nyquist
plots in equivalent circuit (Figure 9) are displayed in Table 4.
The value of RP increases with increase in inhibitor concen-
tration due to more number of CD1 and CD2 molecules
adsorbed on the MS surface which increase surface coverage. It
can be seen from Table 4 that the value of Cdl decreases with
the addition of CD1 and CD2. These values continuously
decrease with increasing inhibitor concentration, due to
decrease in local dielectric constant and increase in the
electrical double-layer thickness.[34] The χ2 values lies within the
range, supported good quality of fitting of equivalent circuit
used.
Bode plots of CD1 and CD2 are displayed in Figure 10. The
single peak found in these plots suggested the presence of one
time constant. The increase in phase angle with increase in
concentration of CD1 and CD2, results in widening of peak due
to higher adsorption of CD1 and CD2 on MS surface
2.6. Potentiodynamic Polarization study (PPS)
Potentiodynamic polarization curves with and without inhibitor
are represented in Figure 11. The values of icorr, Ecorr, anodic
Tafel slope (βa), cathodicTafel slope (βc) and η %, were obtained
from Tafel curves and portrayed in Table 5. The nature of Tafel
curves remain same with and without inhibitor reflects that
Figure 9. Nquist plots of (a) CD1 (b) CD2
Figure 10. Bode plots of (a) CD1 (b) CD2
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Figure 11. Tafel plots of (a) CD1 (b) CD2
Table 5. EIS parameters for (a) CD1 (b) CD2.
Conc. (ppm)
Blank
CD1
10
25
50
75
100
CD2
10
25
50
75
100
βa
(mV dec-1)
-βc
(mV dec-1)
icorr
(μAcm 2)
η%
497
493
236
286
232
278
5207
1640
–
68.5
500
509
504
507
497
304
325
351
369
285
297
306
343
355
270
1061
802.6
382.3
287.3
1932
79.6
84.5
92.6
94.4
62.8
500
506
495
494
291
307
313
358
282
295
311
320
1491
1142
766.8
476.9
71.3
78.0
85.2
90.8
concentration, anodic and cathodic curves moves towards
lower current density which suggested the mixed type nature
of both inhibitors. It is inferred from Table 5 that h % enhances
with enhance in inhibitor concentration due to adsorption of
CD1 and CD2 on MS surface. From Table 5, it can be seen that
the change in Ecorr values is very small (16 mV) in presence of
both CD1 and CD2 with respect to blank, suggested that both
inhibitors are mixed type inhibitor.[35]
Figure 12. Complex spectra of CD1
Table 4. Potentiodynamic polarization parameters of (a) CD1 (b) CD2.
Conc.
(ppm)
RS
(Ω
cm2)
RP
(Ωcm2
)
Y0
(μFcm 2)
n
Cdl
(μF
cm2)
η %
χ2
Blank
CD1
10
25
50
75
100
CD2
10
25
50
75
100
0.972
1.14
5.36
16.4
1994
876.7
0.833
0.8135
802.7
331.5
–
67.3
1.4 × 10
2.3 × 10
4
1.16
1.48
1.26
1.09
1.05
23.38
35.52
53.96
97.63
13.82
567.6
489.5
484.4
215.7
1016
0.8367
0.8088
0.7407
0.7775
0.7766
244.1
187.8
135.2
71.4
297.8
77.0
84.9
90.0
94.5
61.2
3.2 × 10
4.4 × 10
5.3 × 10
6.8 × 10
2.5 × 10
4
1.03
1.15
1.09
1.11
18.5
24.58
32.61
49.71
805.9
753.5
555.9
489.8
0.7899
0.7533
0.7965
0.7054
263.2
204.0
199.5
103.7
71.0
78.1
83.5
89.2
3.6 × 10
4.8 × 10
5.4 × 10
7.9 × 10
4
4
2.7. XPS analysis
4
4
4
4
4
4
4
mechanism of corrosion is same with and without inhibitor.
From Figure 11, it is visible that on enhancing inhibitor
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Ecorr
(mV vs SCE)
The XPS analysis was done to acquire a detailed understanding
about composition of adsorbed layer of studied corrosion
inhibitors on MS surface. The observed XPS spectra of CD1 and
CD2 are embodied in Figure 12, 13 and 14, 15 respectively. Fig.
12 and 14 shows the peaks corresponding to all the elements
present in CD1 and CD2 respectively. Thus it can be concluded
that adsorption of CD1 and CD2 is taking place on the surface
of MS.
The CD1deconvulated XPS spectra of C1s (Figure 13 a)
could be fitted into five peaks which centered at 284.5, 285.9,
287.6, 291.4 and 293.6 eV, assigned to the C=C or C C,[36]
C=N,[16] C=S,[37] O-C=O[38] and π-π* transition[40] respectively. In
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Figure 13. XPS spectra of CD1 (a) C 1s (b) N 1s (c) S 2p (d) O 1s (e) Fe 2p
Figure 14. Complex spectra of CD2
ChemistrySelect 2020, 5, 7347 – 7357
the case of CD2 (Figure 15 a) C1s peak could be fitted into
283.6, 286.8, 291.2 and 294.1 eV, corresponding to the C=C or
C C,[39] C=N,[16] O-C=O[38] and π-π* transition[40] respectively. The
S2p spectra of CD1 (Figure 13b) displayed three peaks at 163.2,
168.2 169.1 eV, which could be allotted to the C=S,[20] S-Fe[44]
and sulfates[45] respectively. The N1s spectra of CD1 (Figure 13
c) and CD2 (Fig. 15 b) shows two peaks at 399.5,[41] 401.6[42] and
398.6,[43] 400.5 eV[42] respectively, which could be allotted to the
N Fe and positively charged nitrogen (-N +).
The deconvulation of O1s spectra of CD1 (Figure 13 d)
could be fitted into two peaks, at 531.2 eV, corresponding to
the O2 associated to the oxygen atom bonded with Fe2O3 and
Fe3O4 oxides[46] and 531.2 eV attributed to the C=O bond.[48]
While XPS of CD2 (Figure 15 c) could be fitted into three peaks
at 529.9 eV, corresponding to the O2 bonded with Fe3 + in
Fe2O3 oxides,[48] 528.8 eV due to adsorbed oxygen[47] and
530.5 eV due to C=O.[48]
The Fe 2p spectra of CD1 (13 e) and CD2 (15 d) shows
peaks at binding energy 712.2 and 711.3 eV respectively
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Figure 15. XPS spectra of CD2 (a) C 1s (b) N 1s (c) O 1s (d) Fe 2p
Figure 17. AFM images of MS (a) Planer (b) after submerged in without
inhibitor (blank) (c) with CD1 (d) with CD2
Figure 16. SEM images of MS (a) Planer (b) after submerged in without
inhibitor (blank) (c) with CD1 (d) with CD2
corresponding to Fe 2p3/2 which are allotted to ferric
compounds like Fe2O3 and FeOOH.[44]
ChemistrySelect 2020, 5, 7347 – 7357
The protective layer formation of Fe2O3 and FeOOH reduces
ionic diffusion and enhance corrosion protection of MS sample.
The peaks of CD1 and CD2 at binding energy at 726.5 and
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725.3 eV respectively attributed to Fe 2p1/2 are properties of
Fe (II) species.[43]
2.8. SEM analysis
SEM micrographs of MS coupons were taken before and after
submerged in 15 % HCl solution with and without CD1 and
CD2 as reflected in Figure 16.
Figure 16 (a) shows the polished MS surface without
contact to the corrosive solution. The SEM of polished sample
(16 a) is almost smooth with minor abrasive scratches. Figure 16 (b, c, d) shows the MS surface after submerged in 15 %
HCl solution without and with CD1 and CD2 respectively. The
SEM micrograph manifest that MS surface was badly damaged
without inhibitor (Figure 16 b) with more number of cracks and
pits. But in the presence of inhibitor (Figure 16 c, d) MS surface
was notably improved with less cracks and pits as comparison
to the MS surface without inhibitor. This improvement is
because of the inhibitive layer formation on MS surface. The
good inhibition ability of inhibitor to adhere MS surface is due
to the lone pair of Nitrogen, Sulfur and π electrons, blocking
active sites, hence reducing rate of corrosion.
2.9. AFM analysis
The 3D AFM images were displayed in Figure (17 a, b, c, d).
Figure 17a & b are the AFM images of polished sample and
sample after immersion in 15 % HCl solution without inhibitor
with average roughness of 11.5 and 202 nm, respectively. In
presence of CD1 and CD2 (Fig. 17 c & d) average roughness is
found as 27.4 and 56 nm respectively. The reduction in average
surface roughness in presence of inhibitor as compare to in
absence of inhibitor suggested the adsorption of CD1 and CD2
on MS surface. The lower average roughness value of CD1 than
CD2 indicates more efficient adsorption of CD1 than CD2,
resulting better inhibition efficiency of CD1 as compare to CD2.
3. Conclusion
CD1 and CD2 are good eco-friendly corrosion inhibitor for MS
in 15 % HCl solution. The observed h % of CD1 and CD2 at
100 ppm is 96.4 and 90.00 %, respectively, at 303 K. Corrosion
inhibition efficiency increases with increase in concentration
and decreases with increase in concentration of CD1 and CD2.
Adsorption of CD1 and CD2 on MS surface followed Langmuir
adsorption isotherm model. The values of ~Gads and ~Hads
suggested that adsorption of studied inhibitors is physisorption. Potentiodynamic measurement indicates that CD1 and
CD2 are mixed type inhibitor. EIS studies suggested that charge
transfer resistance increases with increase in concentration
whereas double layer capacitance decreases on increasing
concentration of CD1 and CD2, suggesting adsorption of
inhibitors on the surface of mild steel. SEM, AFM and XPS
confirmed the formation of protective layer of CD1 and CD2 on
MS surface.
ChemistrySelect 2020, 5, 7347 – 7357
Supporting Information Summary
The experimental section can be found in supporting information.
Conflict of Interest
The authors declare no conflict of interest.
Keywords: AFM · Carbon dots · Corrosion mitigation · Mild
steel · SEM · XPS
[1] B. Thirumalairaj, M. Jaganathan, Egypt. J. Pet. 2016, 25, 423–432.
[2] E. Gutierrez, J. A. Rodriguez, J. C. Borbolla, J. G. A. Rodriguez, P.
Thangarasu, Corros. Sci. 2016, 108, 23–35.
[3] Y. Qiang, S. Zhang, L. Guo, X. Zheng, B. Xiang, S. Chen, Corros. Sci. 2017,
119, 68–78.
[4] A. S. Singh, S. Thakur, B. Pani, E. E. Ebenso, M. A. Quarishi, A. K. Pandey,
ACS Omega 2018, 3, 4695–4705.
[5] G. Khan, W. J. Basirun, N. S. Kazi, P. Ahmed, L. Magaji, S. M. Ahmed, G. M.
Khan, M. A. Rehman, J. Colloid Interface Sci. 2017, 502, 134–145.
[6] V. Saraswat, M. Yadav, J. Mol. Liq. 2019, 297, 111883.
[7] M. Yadav, T. K. Sarkar, T. Purkait, J. Mol. Liq. 2015, 212, 731–738.
[8] V. Saraswat, M. Yadav, I. B. Obot, Colloid Surface A 2020, 599, 124881.
[9] E. Kowsari, S. Y. Arman, M. H. Shahini, H. Zandi, R. Naderi, A.
Pourghasemihanza, M. Mehdipour, Corros. Sci. 2016, 112, 73–85.
[10] A. Y. E. Etre, M. Abdallah, Z. E. E. Tantawy, Corros. Sci. 2005, 47, 385–395.
[11] Y. Qiang, S. Zhang, S. Yan, X. Zou, S. Chen, Corros. Sci. 2017, 126, 295–
304.
[12] Y. Qiang, S. Zhang, B. Tan, S. Chen, Corros. Sci. 2018, 133, 6–16.
[13] X. Li, M. Rui, J. Song, Z. Shen, H. Zeng, Adv. Funct. 2015, 25, 4929–4947.
[14] H. Yu, R. Shi, Y. Zhao, G. I. N. Waterhouse, L. Z. Wu, C. H. Tung, T. Zhang,
Adv. Mater. 2016, 28, 9454–9477.
[15] Y. Song, C. Zhu, J. Song, H. Li, Y. Lin, Appl. Mater. Interfaces 2017, 9,
7399–7405.
[16] Y. Ye, D. Yang, H. Chen, J. Mater. Sci. Technol. 2019, 35, 2243–2253.
[17] Y. Ye, D. Yang, H. Chen, S. Guo, Q. Yang, L. Chen, H. Zhao, L. Wang, J.
Hazard. Mater. 2020, 381, 121019.
[18] Y. Ye, Y. Zou, Z. Jiang, Q. Zang, L. Chen, S. Guo, H. Chen, J. Alloys Compd.
2020, 815, 152338.
[19] D. Yang, Y. Ye, Y. Su, D. Gong, H. Zhao, J. Clean. Prod. 2019, 229, 180–
192.
[20] C. Hongyu, C. Zhenyu, G. Xingpeng, J Taiwan Inst. Chem. Eng. 2019, 99,
224–238.
[21] M. Cui, S. Ren, Q. Xue, H. Zhao, L. Wang, J. Alloys Compd. 2017, 726, 680–
692.
[22] Y. Qiang, S. Zhang, H. Zhao, B. Tan, L. Wang, Corros. Sci. 2019, 161,
108193
[23] Y. Ye, D. Zhang, Y. Zou, H. Zhao, H. Chen, J. Clean. Prod. 2020, 264,
121682.
[24] Y. Ye, Z. Jiang, Y. Zou, H. Chen, S. Guo, Q. Yang, L. Chen, J. Mater. Sci.
Technol. 2020, 43, 144–153.
[25] X. Ran, Q. Qu, X. Qian, W. Xie, S. Li, L. Li, L. Yang, Sensor Actuat B-Chem.
2018, 257, 362–371.
[26] M. Mobin, S. Zehra, R. Aslam, RSC Adv. 2016, 6, 5890–5902.
[27] H. A. Sorkhabi, B. Shaabani, D. Seifzadeh, App. Surf. Sci. 2005, 239, 154–
164.
[28] S. M. A. Hosseini, M. Salari, E. Jamalizadeh, S. Khezripoor, M. Seifi, Mater.
Chem. Phys. 2010, 119, 100–105.
[29] M. Yadav, S. Kumar, R. R. Sinha, I. Bahadur, E. E. Ebenso, J. Mol. Liq. 2015,
211, 135–145.
[30] F. S. DeSouza, C. Giacomelli, R. S. Gonçalves, A. Spinelli, Mater. Sci. Eng. C
2012, 32, 2436–2444.
[31] P. B. Matad, B. P. Mokshanatha, N. Hebbar, V. T. Venkatesha, H. C.
Tandon, Ind. Eng. Chem. Res. 2014, 53, 8436–8444.
[32] M. A. Hegazy, M. Abdallah, M. K. Awad, M. Rezk, Corros. Sci. 2014, 81, 54–
64.
7356
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemistrySelect
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[41]
Full Papers
doi.org/10.1002/slct.202000625
M. Mobin, M. Rizvi, Carbohydr. Polym. 2017, 160, 172–183.
Y. Qiang, S. Zhang, L. Wang, Appl. Surf. Sci. 2019, 492, 228–238.
P. Singh, M. A. Quraishi, Measurment 2016, 86, 114–124.
N. Zhou, X. Zhang, Y. Shi, Z. Li, Z. Feng, New J. Chem. 2018, 42, 14332–
14339.
J. Peeling, F. E. Hruska, D. M. McKinnon, M. S. Chauhan, N. S. Mcintyre,
Can. J. Chem. 1978, 56, 2405–2411.
S. Stankovich, R. D. Piner, X. Chen, N. Wu, S. T. Nguyen, R. S. Ruoff, J.
Mater. Chem. 2006, 16, 155–158
R. Vicentini, L. H. Costa, W. Nunes, O. V. Boas, D. M. Soares, T. A. Alves, C.
Real, C. Bueno, A. C. Peterlevitz, H. Zanin, J. Mater. Sci. Mater. 2018, 29,
10573–10582.
M. Xue, L. Zhang, M. Zou, C. Lan, Z. Zhan, S. Zhao, Sensor Actuat B-Chem.
2015,19, 50–56.
M. A. M. El-Haddad, A. B. Radwan, M. H. Sliem, W. M. I. Hassan, M. M.
Abdullah, Sci. Rep. 2019, 9, 1–15.
ChemistrySelect 2020, 5, 7347 – 7357
View publication stats
[42] O. Olivares-Xometl, N. V. Likhanova, R. Martınez-Palou, M. A. DomınguezAguilar, Mater. Corros. 2009, 60, 14–21.
[43] N. N. Z. Hashim, H. E. Anouar, K. Kassim, H. M. Zaki, A. I. Alharthi, Z.
Embong, Appl. Surf. Sci. 2019, 476, 861–877.
[44] M. Tourabi, K. Nohair, M. Traisnel, C. Jama, F. Bentiss, Corros. Sci. 2013,
75, 123–133.
[45] M. Fantauzzi, B. Elsener, D. Atzei, A. Rigoldi, A. Rossi, RSC Adv. 2015, 5,
75953–75963.
[46] P. Singh, V. Srivastava, M. A. Quraishi, J. Mol. Liq. 2016, 216, 164–173.
[47] L. Armelao, D. Barreca, G. Bottaro, S. Gross, Surf. Sci. Spectra 2003, 10,
137–142.
[48] M. Li, C. Bian, G. Yang, X. Qiang, Chem. Eng. 2019, 368, 350–358.
Submitted: February 14, 2020
Accepted: June 15, 2020
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