Nghiên cứu biến tính màng epoxy và nền thép nhằm nâng cao khả năng chống ăn mòn tt tiếng anh

THE UNIVERSITY OF DANANG
UNIVERSITY OF SCIENCE AND EDUCATION


DUONG THI HONG PHAN

IMPROVING CORROSION PROTECTION OF EPOXY
RESIN BY THE MODIFIED EPOXY AND CONVERSION
COATING ON METAL SUBSTRATE

Major: Organic Chemistry
Code: 94440114

SUMMARY OF DISSERTATION ON DOCTOR OF
PHILOSOPHY IN CHEMISTRY

DaNang, 2019


The dissertation was completed at
THE UNIVERSITY OF SCIENCE AND EDUCATIONTHE UNIVERSITY OF DANANG

Scientific Supervisors:
1. Prof.Dr.Dao Hung Cuong
2. Asc.Prof.Dr. Le Minh Duc
1st Reviewer: .............................................................................
2nd Reviewer: .............................................................................
3rd Reviewer: .............................................................................

The dissertation will be defended at The University of
Danang-The University of Science and Education at…………..

The :
National library of Viet Nam;
The library of The University of Science and Education-The
University of DaNang.


1
PREFACE
1. Reasons for choosing the dissertation: In the paint industry,
titanium dioxide (TiO2) is a white, solid, non-toxic, inexpensive and
fast colour. In anti-corrosion properties terms, TiO2 nanotubes are
capable of extending the erosion time through the coating of
corrosion agents than TiO2 nanoparticles. However, TiO2
nanoparticles were dispersed in resin difficult to achieve
homogeneity because of their high surface energy leading to easy
aggregation and clotting, especially in high viscosity epoxy resins.
Once well dispersed, mechanical, durability, heat resistance and anticorrosion properties were improved. Physical distribution is not
enough but also a combination of physical and chemical methods.
Therefore, we conducted a study on synthesis of TiO2 nanotubes and
the grafting surface of TNTs with silane coupling agent called 3aminopropyl triethoxylsilane (APTS) to increase homogeneity by
entropy mechanism. Besides, the molybdate conversion coating was
highly appreciated to replace chromate (VI) ions in the field of metal
protection by not only similar good corrosion resistance but also
harmless inhibitor. However, molybdate conversion coating was
more effective in the presence of oxidizing compounds. In addition,
the Ti/Zr oxidizing compounds have also been rated for its ability to
safe on steel surfaces in recent decades. Therefore, the Zr/Ti/Mo
conversion coating on the steel subtrates by chemical methods to
improve the substrate protection was part of the dissertation. For

those reasons, we propose the dissertation : “ Improving corrosion
protection of epoxy resin by the modified epoxy and conversion
coating on metal substrate”.
2. The objects of the dissertation: Epoxy paint coating for metal
protection by the grafted APTS on TiO2 nanotubes. Simultaneously,


2
steel subtrates were coated with the Zr/Ti/Mo conversion coating to
improve the steel protection.
3. Contents of the dissertation: processing and coating of Zr/Ti/Mo
layer; studying surface and composition of Zr/Ti/Mo coating on the
steel surface by SEM/EDX methods; studying the mechanical
properties of the coating; evaluating the corrosion resistance of
Zr/Ti/Mo conversion coating by EIS and salt spray method; physical
and thermal properties of epoxy resins using APTS-TNTs pigment;
evaluating the corrosion resistance of that epoxy resins by EIS and
salt spray methods.
4. Methods: material analysis methods: X-ray diffraction, scanning
electron microscopy, BET, TEM, FTIR, TGA and DSC; evaluating
methods for the mechanical properties of paint film: tape adhesion,
impact resistance, and film hardness, flexural strength; Anticorrosion evaluation methods: Tafel extrapolation polarization, salt
spray methods and EIS; mathematical methods.
5. New contributions of the dissertation : The grafted APTS on
TiO2 nanotubes were enhanced the corrosion resistance of epoxy
coating. On the other hand, the steel surfaces were protected by the
Zr/Ti/Mo conversion coating that was capable of chromate (VI) ions
replacing in the future.
6. The composition of the dissertation: The dissertation consists of
112 pages, including 25 tables and 75 photographs. Introduction, 05

papers; Conclusions and recommendations, 02 papers; Published
works, 01 paper; Reference, 12 papers. The main content of the
dissertation is divided into three chapters: Chapter 1. Overview, 22
papers; Chapter 2. Methods and experiments, 23 papers and Chapter
3. Results and Discussion, 47 papers.


3
CHAPTER 1. OVERVIEW
1.1. Introduction to epoxy coating using APTS-TNTs pigments
1.1.1. Titatnium dioxide nanotubes
1.1.2. Silane coupling agent
1.1.3. Epoxy resin
1.1.4. Overview of research on epoxy coating
1.2. Introduction to conversion coating on steel substrate
1.2.1. Corrosion of metals
1.2.2. Conversion Coating
1.2.3. Overview of research on conversion coating on steel
substrate
In summary, it can be seen that epoxy resin is one of the
most thermoplastic resins in the paint industry, especially epoxy
resins from bisphenol A. According to the published results, there are
many studies about highly anti-corrosion epoxy coating used the
grafted-TiO2 nanoparticles by chemical method on their surfaces. In
addtions, studies have shown that TiO2 nanotubes are more corrosion
resistant than nanoparticles. However, epoxy coating using TiO2
nanotubes pigments for anticorrosion was not attracted but mainly
focus on their photocatalytic effects. On the other hand,
uncomprehensive published research on the process of producing
epoxy coating using APTS-TNTs has been improved corrosion

resistance. From the above characteristics, it can be seen that the
epoxy coating using APTS-TNTs pigment was a potential coating in
the anti-corrosion coating.
Moreover, there are no research has been published on the
Zr/Ti/Mo conversion coating, but mainly on single or double-metal
conversion coatings with steel protection purposes. Therefore, the


4
study of multi-metal Zr/Ti/Mo conversion coating was essential to
improve the protection of steel substrate. For those reasons, we
propose the dissertation : “ Improving corrosion protection of
epoxy resin by the modified epoxy and conversion coating on
steel substrate”.
CHAPTER 2: METHODS AND EXPERIMENTS
2.1. Experiment
2.2. Methods
- Material analysis methods: X-ray diffraction, scanning
electron microscopy, BET, TEM, FTIR, TGA and DSC.
- Evaluating methods for the mechanical properties of paint
film: tape adhesion, impact resistance, and film hardness, flexural
strength.
- Anti-corrosion evaluation methods: Tafel extrapolation
polarization, salt spray methods and EIS; mathematical methods.
- Mathematical methods: experimental planning for level II
of Box and Hunter, optimization by the excell-solver program,
processing of empirical data.
CHAPTER 3: RESULTS AND DISCUSSION
3.1. Epoxy coating using APTS-TNTs pigment
3.1.1. Synthesis of Titanium dioxide nanotubes (TNTs)

5

Figure 3.1. XRD patterns of obtained TNTs aggregates calcined at
400, 900 and 1000oC.

Figure 3.3 TEM images of a) TiO2 nanoparticles before synthesis,
b) TiO2 nanotubes , c) TNTs dimension
Conclusion 1: Titanium dioxide nanotubes were synthesized
via hydrothermal methods from P-25 Degussa TiO2 powders. The
lengths of these TNTs ranged from 100-150 nm, and the diameter of


6
the tubular materials are almost uniform around 10-15 nm. The
surface area of TNTs is 188 m2/g at 140oC.
3.1.2. APTS-grafted TiO2 nanotubes

Figure 3.5. Thermogravimetric analysis of unmodified TNTs (curve
(a) and APTS-modified TNTs (curve (b)).

Figure 3.9. Chemical grafting of APTS coupling agents onto
TNT surfaces.


7

Figure 3.10. APTS hydrolysis occurred in the aqueous mixing
process.

Table 3.1. The grafting efficiency of 20 samples with different
concentrations, reaction durarions and various temperatures.
x1
(%KL)

x2
(oC)

x3
(phút)

Eg

+

+

+

5,029

2

-

+

+

4,397

3

+

-

+

5,687

4

-

-

+

5

+

+

6

-

7

+

8

-

STT
1

2k

2k

x1
(%KL)

x2
(oC)

x3
(phút)

Eg

11

0

-α

0

3,795

12

0

+α

0

5,475

13

0

0

-α

3,276

3,670

14

0

0

+α

4,595

-

4,351

15

0

0

0

5,228

+

-

3,402

16

0

0

0

5,473

-

-

4,661

17

0

0

0

5,332

-

-

2,966

18

0

0

0

5,309

STT

2k

no

9

-α

0

0

2,860

19

0

0

0

5,329

10

+α

0

0

5,230

20

0

0

0

5,279


8

Figure 3.11. FTIR spectra of various TNTs: (a) unmodified TNTs
and (b) APTS-modified TNTs.

Figure 3.12. (a) Representative TEM image and (b) highmagnification TEM image with measured withs and lengths of APTSTNTs.


9

Conclusion 2:
- Titanium dioxide nanotubes (TNTs) were surface-modified with 3aminopropyl triethoxysilane (APTS) by an aqueous process at
reaction conditions: 190 wt.% APTS/TNTs, 70oC and 337 mins in
this study.
- The morphology and the tubular size of TNTs after APTS
modification were unchanged in the grafting process
3.1.3. Dispersion process of APTS-TiO2 into epoxy resin

Figure 3.14. Schematic of the structure of the grafted TNTs/epoxy resin.


10

Figure 3.15. FTIR spectra of a) TiO2 nanotubes/epoxy coating and b)
APTS-grafted TiO2 nanotubes/epoxy coatings.
3.1.4. Mechanical behavior of epoxy/(TiO2 nanotubes and APTSgrafted TiO2 nanotubes) composite coatings.
The resulting data of 9 epoxy coating samples including
unmodified (1, 3, 5 and 7 wt.%) and modified-TiO2 (1, 3, 5 and 7 wt.%)
nanotubes/ epoxy coatings are shown in Table 3.4.
Table 3.4. Machenical resistance performance of 09 epoxy/nanofiller
coated panels.
Samples

Flexibility

( mm)

Hardness
Adhesion
(N)

Impact
(cm)

Epoxy

20

5B

1

15

1 wt.% TiO2 nanotubes

10

2B

1

40

1 wt.% APTS-TiO2 nanotubes

10

2B

1

40

3 wt.% TiO2 nanotubes

10

H

1

40

3 wt.% APTS-TiO2 nanotubes

10

F

1

50

5 wt.% TiO2 nanotubes

10

H

1

55


11
5 wt.% APTS-TiO2 nanotubes

10

F

1

75

7 wt.% TiO2 nanotubes

10

H

1

75

7 wt.% APTS-TiO2 nanotubes

10

H

1

75

3.1.5 Thermal behavior of epoxy/TNT nanocomposite coating
Table 3.5. Summary of TGA results for TiO2 nanotubes/ epoxy
nanocomposite coatings and APTS-grafted TiO2 nanotubes/ epoxy
nanocomposite coatings at different contents.
Temp. of weight loss
Nanocomposite

Residual char
at 600oC
(wt.%)

10 wt.%,

80 wt.%

1 wt.% TiO2 nanotubes

333

434

12.5

3 wt.% TiO2 nanotubes

337

483

15.5

5wt.% TiO2 nanotubes

336

487

16.7

7 wt.% TiO2 nanotubes

343

618

20.5

1 wt.% APTS-grafted TiO2 nanotubes

340

447

14.3

3 wt.% APTS-grafted TiO2 nanotubes

341

450

16.6

5 wt.% APTS-grafted TiO2 nanotubes

343

580

19.3

7 wt.% APTS-grafted TiO2 nanotubes

343

605

20.4

Table 3.6. Summary of Tg results for TiO2 nanotubes/ epoxy
nanocomposite coatings and APTS-grafted TiO2 nanotubes/ epoxy
nanocomposite coatings at different contents.
Nanocomposites
Epoxy
3 wt.% TiO2 nanotubes
3 wt.% APTS-grafted TiO2 nanotubes
5 wt.% TiO2 nanotubes
5 wt.% APTS-grafted TiO2 nanotubes
7 wt.% TiO2 nanotubes
7 wt.% APTS-grafted TiO2 nanotubes

Tg (oC)

105
106
107
108
109
111
111


12

3.1.6. Corrosion resistance of epoxy/(TiO2 nanotubes and APTSgrafted TiO2 nanotubes) composite coating.
The salt spray test results are shown in Figure 3.22 and
detailed summary in Table 3.7.

Figure 3.22. Salt spray corrosion test after a) 500 h exposure of epoxy/ 5

wt.% TiO2 nanotubes coating, b) 500h exposure and c) 672h exposure of
epoxy/5 wt% APTS-grafted TiO2 nanotubes coating.

Table 3.7. Corrosion resistance performance of epoxy/ 5 wt.% TiO2
nanotubes coating and epoxy/5 wt% APTS-grafted TiO2 nanotubes
coating after time of exposure in salt spray cabinet.
Samples
5 wt.% TiO2nanotubes
5 wt.% APTS-grafted TiO2 nanotubes
5 wt.% APTS-grafted TiO2 nanotubes
5 wt.% APTS-grafted TiO2 nanotubes

Time of
exposure
(h)
272
272
361
529

Scribe failure
rating no.
(ASTM-D1654)
1
10
5
1


13

Figure 3.23. Barrier mechanism in coating pigmented with TiO2
nanotubes and APTS grafted-TiO2 nanotubes.
Figure 3.24 shown Nyquist plot for the impedance
spectroscope of epoxy/ 5 wt.% TiO2 nanotubes coating and epoxy/5
wt% APTS-grafted TiO2 nanotubes coating. Epoxy/ 5 wt.%
TiO2nanotubes coating began to appear the second semi-circle,

indicated that the erosion of the steel substrate had begun. Steel
substrates are protected in 59h for epoxy/5 wt% APTS-grafted TiO2
nanotubes coating and 48h for epoxy/ 5 wt.% TiO2 nanotubes
coating. The test demonstrated that the modified TiO2 nanotubes to
the primer could have more positive effect than unmodified ones on
the corrosion resistance.


14

Figure 3.24. Nyquist plot for the impedance spectroscope of epoxy
coating included a) TiO2 nanotubes and b) APTS-TiO2 nanotube in
3.5 wt% NaCl solution.
Based on the impedance analysis of Figures 3.24, we
proposed an equivalent circuit model, as shown in Figure 3.25


15

Figure 3.25. Equivalent circuit modes of epoxy coating/ steel
substrate following immersed time.
3.1.7 Proposed process for fabricating epoxy/APTS-TiO2 nanotubes

coating to improve the corosion resistance of steel substrate.

Figure 3.27. Process for fabricating epoxy/APTS-TiO2 nanotubes
coating
3.2. Conversion coating based on Zr/Ti/Mo compounds.
3.2.1. Affecting factors of Ecorr


16
Table 3.9. The Ecorr of 31 samples with different concentrations, pH.
x1
x2
x3
x4
(g/L) (g/L) (g/L)
1
-

-0,40

17

2

+

-

-

-

-0,42

18

+α

0

3

-

+

-

-

-0,39

19

0

4

+

+

-

-

-0,41

20

5

-

-

+

-

-0,42

6

+

-

+

-

7

-

+

+

8

+

+

9

-

10

STT

Eă.m

STT

x1
x2

x3
(g/L) (g/L) (g/L)
-α
0
0

x4

Eă.m

0

-0,38

0

0

-0,39

-α

0

0

-0,32

0

+α

0

0

-0,34

21

0

0

-α

0

-0,36

-0,43

22

0

0

+α

0

-0,38

-

-0,37

23

0

0

0

-α

-0,50

+

-

-0,38

24

0

0

0

+α

-0,42

-

-

+

-0,32

25

0

0

0

0

-0,31

+

-

-

+

-0,32

26

0

0

0

0

-0,33

11

-

+

-

+

-0,39

27

0

0

0

0

-0,31

12

+

+

-

+

-0,39

28

0

0

0

0

-0,32

13

-

-

+

+

-0,28

29

0

0

0

0

-0,33

14

+

-

+

+

-0,24

30

0

0

0

0

-0,31

15

-

+

+

+

-0,31

31

0

0

0

0

-0,32

16

+

+

+

+

-0,30

2k

2k
no

Experiment with optimum conditions, mesured and obtained
Ecor = -0,19 (V) as shown in Figure 3.30. This result was the same to
the theoretical results (Ecor.th= -0,2 (V))


17

Figure 3.30. The polarization curves for base steel and Zr/Ti/Motreated steel samples with optimum conditions.
3.2.2. Surface morphology and composition
Table 3.11. Semiquantitative XRF analysis on intermetallic particles
of treated samples. (100µm of thinner).
Memo
Mo

Mass (wt.%)
26,9219

Zr

1,7487

Ti

71,3294

The surface structure of Zr/Ti/Mo treated steel was quite
special structure compared to the bare steel, showed quite thick flat
surfaces.


18

Figure 3.33.SEM images of a) untreated sample, c) treated steel
surface and EDS spectrum of c) untreated sample, d) treated steel
surface.
3.2.3. Adhension measurements
Tap adhension of Zr/Ti/Mo conversion coating filming of
steels were obtained 5B classification due to the edges of the cuts are
completely smooth, none of the squares of the lattice is detached.
The hardness of film was obtained F classification, as shown in
Table 2.6.


19
Table 3.12. Machenical resistance performance of Zr/Ti/Mo-treated
film..
Samples

Flexibility

Hardness

( mm)

(N)

10

F

Zr/Ti/Mo-CC

Adhesion

1

Impact
(cm)

1050

3.2.4. Corrosion tests
Table 3.13 shows the results for salt sprays tests of the
untreated/ED coatings and Zr/Ti/MoCC/ED-coatings.

Figure 3.38. Salt spray corrosion test of untreated- ED coating after
(a) 272 h exposure and Zr/Ti/MoCC-ED coating surfaces after (b)
272 h, (c) 361 h and (d) 529 h exposure.


20

Figure 3.39. Nyquist plot for the impedance spectroscope of a)

photphate coating and b) photphate coating after 30 days in 3.5
wt.% NaCl solution.

Figure 3.40. Nyquist plot for the impedance spectroscope of a)
Zr/Ti/MoCC-ED coating and b) Zr/Ti/MoCC-ED coating after 31 days c)
Zr/Ti/MoCC-ED coating after 32 days in 3.5 wt% NaCl solution.


21
Table 3.13. Corrosion resistance performance of untreated-ED
coating and Zr/Ti/MoCC-ED coating on JISG 3141 substrates after
time of exposure in salt spray cabinet..
Time of exposure

Scribe failure rating

Untreated/ED coating

(h)
272

no. (ASTM-D1654)
4

Zr/Ti/MoCC-ED coating

272

10

Zr/Ti/MoCC-ED coating

361

8

Zr/Ti/MoCC-ED coating

529

4

Samples

Figure 3.40. Equivalent circuit modes of Zr/Ti/MoCC-ED coating/
steel substrate following immersed time.
3.2.5. Proposed process for fabricating Zr/Ti/MoCC-ED coating to
improve the corosion resistance of steel substrate.


22

Figure 3.41. Process for fabricating Zr/Ti/MoCC-ED coating
CONCLUSION
A. Conclusion:
After the implementation process, the dissertation has achieved some
results.
1. The APTS-grafted TiO2 nanotubes/ epoxy nanocomposite
showed better corrosion resistance than TiO2 nanotubes/ epoxy
nanocomposite. Standing 672 h exposure, the corrosion resistance of

epoxy resin greatly improved by using reinforcing the APTSmodified TNTs.


23
2. Titanium dioxide nanotubes (TNTs) were surface-modified
with 3-aminopropyl triethoxysilane (APTS) by an aqueous process at
reaction conditions: 190 wt.% APTS/TNTs, 70oC and 337 mins in
this study . The lengths of these APTS-TNTs ranged from 100-150
nm, the diameter of the tubular materials are almost uniform around
10-15 nm, anatase crystalline phases and the surface area 188 m2/g.
3. The dispersion capacity of APTS- TiO2 nanotubes in toluene
solvent and in epoxy were better than TiO2 nanotubes because the
amin groups on the modified TiO2 nanotubes interacted with epoxy
groups of the epoxy D.E.H.24.
4. The results showed that surface treatment of TiO2 nanotubes
with APTS improves the impact resistance and bending resistance of
epoxy coating, but unchanged hardness than unmodified- TiO2
nanotubes.The obtained results shown the thermal stability of APTSgrafted TiO2 nanotubes/ epoxy nanocomposite was higher compared
to that of the TiO2nanotubes/ epoxy nanocomposite.
5. Zr/Ti/Mo conversion coating could significantly improve
the corrosion protection properties of the ED coating even at long
immersion times. Scanning electron microscopy with energydispersive X-ray spectroscopy (SEM/EDX) has indicated the surface
structure and the presence of Mo/Zr/Ti on surface of the steel.
6. Passivation layer containing Zr, Ti and Mo has been
successfully carried out on steel by dipping in solution of 17 g/L
Na2MoO4, 7 g/L K2ZrF6, 1 g/L H2TiF6 and pH = 5.The corrosion
potential and current of coating in case of with and without
passivation layer on the steels was determined by potentiodynamic
polarization test, showed that the corrosion current density decreased
when using Zr/Ti/Mo coating.