Curcumin modified graphene oxide (GO-CR) was prepared using adsorption method and polyurethane (PU) coating containing 0.3 wt% GO-CR was prepared on carbon steel. Synthesized GO-CR was characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and zeta potential measurement. Corrosion protection property of polyurethane coating containing GO-CR was evaluated and compared with blank polyurethane coating and coating containing GO by electrochemical impedance spectroscopy. The results showed that GO-CR has layer structure like GO with lower crystallinity. In GO-CR structure curcumin was attached on GO surface. The presence of curcumin on GO-CR surface provided corrosion inhibition action for PU coating and also improved the dispersion of GO in PU coating

Nguyen, Anh Son

Nguyen, Thuy Duong

Nguyen, Tuan Anh

Phan, Thanh Thao

Thi Xuan Hang, To

Tran, Boi An

Vu, Ke Oanh

English

Vietnam Academy of Science and Technology: Journals Online

 
 
Vietnam Journal of Science and Technology 58 (3) (2020) 274-281 
doi:10.15625/2525-2518/58/3/14645 
 
MODIFICATION OF GRAPHENE OXIDE BY CURCUMIN AND 
APPLICATION IN POLYURETHANE COATING  
Thuy Duong Nguyen
1
, Boi An Tran
2, 3
, Thanh Thao Phan
2, 3
, Ke Oanh Vu
1
,                               
Anh Son Nguyen
1
, Tuan Anh Nguyen
4
, Thi Xuan Hang To
1, 3, *
 
1
Institute for Tropical Technology, Vietnam Academy of Science and Technology                      
18 Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam      
2
Institute of Chemical Technology, Vietnam Academy of Science and Technology                        
1 Mac Dinh Chi, District 1, Ho Chi Minh City, Viet Nam     
3
Graduate University of Science and Technology, Vietnam Academy of Science and Technology 
18 Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam 
4
Central Pre-University school for ethnic minority, 2 Tran Phu, Viet Tri, Phu Tho, Viet Nam 
*
Email: ttxhang@itt.vast.vn 
Received:  26 November 2019; Accepted for publication: 7 February 2020  
Abstract. Curcumin modified graphene oxide (GO-CR) was prepared using the adsorption 
method and polyurethane (PU) coating containing 0.3 wt% GO-CR was prepared on carbon 
steel. Synthesized GO-CR was characterized by Fourier transform infrared spectroscopy (FTIR), 
X-ray diffraction (XRD), scanning electron microscopy (SEM) and zeta potential measurement. 
Corrosion protection property of polyurethane coating containing GO-CR was evaluated and 
compared with that of blank polyurethane coating and coating containing GO by electrochemical 
impedance spectroscopy. The results showed that GO-CR has a layer structure like GO with 
lower crystallinity. In GO-CR, structure curcumin was attached on GO surface. The presence of 
curcumin on GO-CR surface provided corrosion inhibition action for PU coating and also 
improved the dispersion of GO in PU coating. 
Keywords: graphene oxide, curcumin, corrosion protection, polyurethane coatings. 
Classification numbers: 2.4.4, 2.9.4, 2.5.3.  
1. INTRODUCTION 
Corrosion of metals causes high economic loss, especially in tropical weather conditions. 
Therefore, corrosion protection of metals is important and necessary. A lot of researches have 
been concentrated on using graphene oxide to develop environmentally friendly organic 
coatings. Graphene oxide can be formed on steel to provide good corrosion protection coatings 
[1 - 3]. Carbonyl iron (CI) particles were treated with 4-aminobenzoic acid (A-CI) then coated 
by graphene oxide by adsorption method. Electrochemical impedance measurements showed 
that GO coating passivated A-CI surface and increased the charge transfer resistance of A-CI 
sample [1]. GO coating was formed on mild steel surfaces by electrophoretic (EPD) method  and 
 
 
Modification of graphene oxide by curcumin and application in polyurethane coating  
 
275 
heat treated at 200 
o
C for 4 h. GO coating increased charge transfer of mild steel and decreased 
it’s corrosion rate by 2 times [2]. In other works, GO prepared with different drying procedures      
were deposited on steel substrate by electrophoretic method for corrosion protection. The results 
showed that the drying temperature influenced the dispersion degree of GO in water, as well as 
on the protection performance of GO coating.  GO dried at lower temperature provided higher 
barrier and corrosion protection coating on steel [3]. GO has also been studied as an additive to 
improve corrosion protection properties of organic coatings. GO was often modified or 
combined with other additives in order to improve the effect of GO in organic coatings [4 - 7]. 
Graphene oxide modified by P-phenylenediamine improved corrosion protection of epoxy 
coatings [4]. Surface treatment by aminosilane and 1,4-butanediol diglycidyl improved their GO 
dispersion in epoxy matrix and effects on corrosion resistance of epoxy coatings [5]. GO 
modified by 3-(Triethoxysilyl)propyl isocyanate and 3-aminopropyltriethoxysilane significantly 
improved corrosion resistance and adhesion properties of silane/epoxy coatings on steel surface 
[6]. GO was grafted with polyethylenimin and applied in waterborne epoxy coating for corrosion 
protection of carbon steel [7]. 
 Recently many researches focused on the development of corrosion inhibitors based on 
plant extracts. Curcumin, a polyphenol compound derived from turmeric, showed inhibition 
effect for carbon steel [8 - 10]. M.K. Mohammed et al. studied the corrosion inhibition of carbon 
steel in 3.5 % NaCl by curcumin. It was shown that curcumin can be adsorbed on steel surface, 
and inhibition efficiency was about 86 % at concentration of 2.7 × 10
-5 
M [8]. Curcumin formed 
a protective film on steel surface and showed both anodic and cathodic inhibition effect in 0.5 M 
H2SO4 [9].  Combination of curcumin and Zn
2+
 exhibited corrosion inhibition efficiency of 93 % 
for carbon steel in seawater [10].  
In this study, GO was modified by curcumin (GO-CR) and applied in polyurethane 
coatings for corrosion protection of carbon steel. Synthesized GO-CR was analyzed by FTIR, 
XRD and SEM. The corrosion resistance of polyurethane coatings containing GO-CR was 
evaluated by electrochemical impedance spectroscopy.  
2. MATERIALS AND METHODS 
2.1. Materials 
Natural graphite was purchased by Sigma-Aldrich. KMnO4 and H2SO4 (95 - 98 %) were all 
supplied by Merck. Curcumin was extracted from turmeric powder from Thanh Son, Phu Tho, 
Viet Nam using acetone as a solvent.  
The polyurethane coating was based on a hydroxyl-bearing polyacrylate (ACRY) as base 
and an aliphatic polyisocyanate (ALIP) as hardener. They were obtained from Nippon 
Polyurethane Industry (NPU). 
2.2. Preparation of graphene oxide 
Graphene oxide was synthesized from expanded graphite powder by modified Hummer’s 
method according to the same procedure described in our previous report [11]. Graphite and 
KMnO4 were gradually added into concentrated H2SO4 solution at 2 
o
C. Then the temperature of 
the mixture was increased to 35 
o
C and kept for 2 hours. After that distilled water was poured to 
the mixture with stirring over 1 h, and then H2O2 was poured to the mixture with stirring over 1 
h. GO was filtered, washed with distilled water and dried in a vacuum oven at 50 
o
C for 24 h. 
 
 
Thuy Duong Nguyen, et al. 
276 
2.3. Preparation of curcumin modified graphene oxide 
0.05 g GO was dispersed in 50 mL distilled water using ultrasonics during 20 min. 20 mL 
ethanol solution containing 0.02 g curcumin  was added progressively to the GO solution with 
magnetic stirring. The mixture was then kept at room temperature with stirring for 24 h. After 
that the GO-CR powder was centrifuged, washed with water, and dried at 80 
o
C in vacuum.  
2.4. Preparation of polyurethane coatings containing GO-CR  
Polyurethane coatings containing GO-CR and GO at concentration of 0.3 wt% were 
prepared on carbon steel. The dimension steel sample was 15 × 10 × 0.2 cm. The steel samples 
were abraded by abrasive papers 400 grades and washed with distilled water and ethanol and 
then dried. GO and GO-CR were dispersed in ACRY resin under magnetic stirring and 
ultrasonic condition, and then the hardener was added to resin containing GO or GO-CR. The 
polyurethane coatings were applied on steel plates by spin coating method. These coatings were 
dried at room temperature for 14 days. The thickness of dried coatings was 30 ± 3 µm. 
2.5. Analytical characterization 
The FTIR spectra were obtained using the KBr method on a Nexus 670 Nicolet 
spectrometer operated at 1 cm
-1
 resolution in the 400–4000 cm−1 region.   
XRD patterns were taken by using Siemens diffractometer D5000 with CuKα radiation 
(0.15406 nm). 
The scanning electron microscope images were taken by using Field emission scanning 
electron microscope Hitachi S-4800. 
The zeta potential measurements of the GO and GO-CR were realized by using 
MALVERN Zetasizer Nano ZS. 
2.6. Electrochemical impedance test  
The corrosion resistance of coating samples was investigated by electrochemical 
impedance test using a Biologic SP300.  A three-electrode system was used: coated steel as 
working electrode, saturated calomel (SCE) as reference electrode and platinum grid as counter 
electrode. The electrochemical impedance test was done with frequency intervals from 10 mHz 
to 100 kHz and the corrosion medium was 3 % NaCl solution. For each coating system, three 
samples were tested. 
3. RESULTS AND DISCUSSION 
3.1. Characterization of curcumin modified graphene oxide 
Structure of curcumin loaded GO was characterized at first by FTIR. FTIR spectra of 
curcumin, GO and GO-CR are shown in Fig. 1. The spectrum of GO revealed the presence of 
C=O, C-O and C=C at 1719, 1385 and 1624 cm
-1
 respectively [12]. In the spectrum of curcumin, 
the band at 1628 cm
-1
 was characteristic of aliphatic C=O and C=C. The bands at 1510 and 1284 
cm
-1
 were attributed to C=C and C-O, respectively [13]. Spectrum of GO-CR presented the 
bands characteristic of C=O, C-O and C=C in GO at 1719, 1385 and 1624 cm
-1
. The bands 
characteristic of C-O in CR were observed also in the spectrum of GO-CR. The band 
characteristic of C=C and C=O of CR at 1628 cm
-1 
was overlapped by the band characteristic of 
C=C in GO. These results revealed the presence of curcumin in GO-CR.  
 
 
Modification of graphene oxide by curcumin and application in polyurethane coating  
 
277 
The XRD patterns of GO and GO-CR are presented in Fig. 2. It is observed that GO-CR 
has the same interlayer distance of 0.79 nm as GO. The pattern of GO is sharper than that of 
GO-CR. This result indicates that GO-CR maintains the structure of GO with lower crystallinity. 
 
Figure 1. FT-IR spectra of curcumin, GO and GO-CR.  Figure 2. XRD patterns of GO and GO-CR. 
SEM images of GO and GO-CR are shown in Fig. 3. GO has a layer structure with a large 
surface. GO-CR exhibits also layer structure similar to GO. The surface of GO is smoother than 
the one of GO-CR. This can be explained by the presence of curcumin on GO-CR surface [14].  
 
Figure 3. SEM photographs of GO and GO-CR. 
Surface property of GO-CR was investigated by measuring zeta potential of GO and GO-
CR at a concentration of 0.03 % in distilled water (Fig. 4). The zeta potentials of GO and GO-
CR were -49.0 mV and -29.1 mV, respectively.  In comparison with GO, the zeta potential of 
GO-CR moved in a positive direction. The change of zeta potential indicates the presence of 
curcumin on GO-CR surface [14]. 
 
GO
500 nm
GO-CR
500 nm
 
 
Thuy Duong Nguyen, et al. 
278 
 
Figure 4. Zeta potentials of GO and GO-CR. 
3.2. Characterization of PU coatings containing GO-CR 
The dispersion degree of GO-CR and GO in PU coating was investigated by SEM. The 
SEM images of cross-section surface of PU coatings containing GO and GO-CR are shown in 
Fig. 5. For PU coatings containing 0.3 wt% GO we can see the layer structure of GO and the 
gaps between GO and PU resin. The size of the gaps were about 150-200 nm. For PU coating 
containing GO-CR, the structures of GO-CR can be also observed, but the slits between GO-CR 
and PU resin were much lower that of PU coatings with GO. The size of the slits was about 50-
100 nm. The results showed that modification by curcumin improved the dispersion of GO-CR 
in PU matrix. 
 
Figure 5. SEM images of polyurethane coatings with GO and GO-CR. 
Corrosion resistance of coating samples was investigated by electrochemical impedance 
test. Fig. 6 presents the impedance diagrams of PU coating, PU containing 0.3 % GO and PU 
coating containing 0.3 % GO-CR after 35 days immersion in 3 % NaCl solution. The impedance 
modulus of PU coating with GO and GO-CR were very high and much higher than that of blank 
PU coatings and the impedance modulus of sample with GO-CR was higher than that of sample 
with GO. The increase of impedance modulus of sample with GO-CR in comparison with that of 
coating with GO can be explained the inhibition effect of curcumin on GO-CR surface [8]. From 
impedance diagrams, impedance modulus at a frequency of 100 mHz (Z100 mHz) were extracted to 
evaluate the corrosion resistance of samples [15]. The variations of Z100 mHz of samples during 
the test are shown in Fig. 7. 
 
 
Modification of graphene oxide by curcumin and application in polyurethane coating  
 
279 
 
Figure 6. Electrochemical impedance diagrams obtained after 35 days test in 3 % NaCl for coating 
samples. 
 
Figure 7. Variation of  Z100mHz values with exposure time to NaCl solution of coating samples. 
After 1 h immersion in NaCl solution, the Z100mHz values of all samples were very close and 
very high (> 10
9
 Ω.cm2). During the first 14 days of testing, The Z100mHz values of all samples 
did not change much. After 21 days, the Z100mHz value of blank PU sample decreased 
significantly, while the Z100mHz values of PU samples with GO and GO-CR were stable. The 
decrease of Z100mHz demonstrates the penetration of electrolyte in the coatings. After 42 days, the 
Z100mHz of PU samples with GO and GO-CR were very high (> 10
9
 Ω.cm2), much higher than 
that of blank PU sample (< 10
8
 Ω.cm2). Sample with GO-CR exhibited higher Z100mHz than 
sample with GO. Higher protection obtained by GO-CR compared with GO can be explained by 
the inhibition effect of curcumin presented in GO-CR and better dispersion of GO-CR in PU 
 
 
Thuy Duong Nguyen, et al. 
280 
resin. The presence of curcumin on GO-CR surface provided corrosion inhibition action at the 
steel/coating interface and improved the compatibility between PU and GO-CR. 
4. CONCLUSIONS 
Graphene oxide modified by curcumin was successfully synthesized by adsorption method. 
GO-CR has a layer structure like GO with curcumin attached on GO surface. Polyurethane   
coatings with GO and GO-CR at concentration of 0.3 wt% were prepared for corrosion 
protection of carbon steel. Corrosion resistance of coatings was evaluated by electrochemical 
impedance test. SEM results showed better dispersion of GO-CR in PU matrix than GO. PU 
coating containing GO-CR provided higher corrosion protection performance than PU coating 
containing GO. The presence of curcumin on GO-CR surface provided corrosion inhibition 
action at the steel/coating interface and enhanced the dispersion of GO-CR in PU matrix.  
Acknowledgements. The authors gratefully acknowledge the financial support of Vietnam Academy of 
Science and Technology for senior researchers under the project number NCVCC 13.04/19-19. 
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MODIFICATION OF GRAPHENE OXIDE BY CURCUMIN AND APPLICATION IN POLYURETHANE COATING

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MODIFICATION OF GRAPHENE OXIDE BY CURCUMIN AND APPLICATION IN POLYURETHANE COATING

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