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 M

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 EDUCATION-

THE UNIVERSITY OF DANANG

Scientific Supervisors:

1 Prof.Dr.Dao Hung Cuong

2 Asc.Prof.Dr Le Minh Duc

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, TiO2nanoparticles 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 anti-corrosion 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 3-aminopropyl 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,

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; Anti-corrosion 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

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

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

- 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

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

x 3

x 1 (%KL)

x 2 ( o C)

x 3 (phút) Eg

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) magnification TEM image with measured withs and lengths of APTS-

high-TNTs

9

Conclusion 2:

- Titanium dioxide nanotubes (TNTs) were surface-modified with aminopropyl triethoxysilane (APTS) by an aqueous process at reaction conditions: 190 wt.% APTS/TNTs, 70oC and 337 mins in this study

3 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

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 grafted TiO2 nanotubes) composite coatings

APTS-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

nanocomposite coatings at different contents

Nanocomposite

Temp of weight loss Residual char

at 600 o C (wt.%)

Table 3.6 Summary of Tg results for TiO2 nanotubes/ epoxy nanocomposite coatings and APTS-grafted TiO2 nanotubes/ epoxy

nanocomposite coatings at different contents

3.1.6 Corrosion resistance of epoxy/(TiO2 nanotubes and grafted TiO2 nanotubes) composite coating

APTS-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

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

Samples

Time of exposure (h)

Scribe failure rating no (ASTM-D1654)

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.% TiO 2 nanotubes coating and epoxy/5 wt% APTS-grafted TiO 2 nanotubes coating Epoxy/ 5 wt.%

TiO 2nanotubes 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 TiO 2nanotubes coating and 48h for epoxy/ 5 wt.% TiO 2 nanotubes coating The test demonstrated that the modified TiO 2 nanotubes to the primer could have more positive effect than unmodified ones on the corrosion resistance

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

Table 3.9 The Ecorr of 31 samples with different concentrations, pH

x 1 (g/L)

x 2 (g/L)

x 3 (g/L) x4 Eă.m

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/Mo-treated 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)

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

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

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

Figure 3.41 Process for fabricating Zr/Ti/MoCC-ED coating

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- TiO 2 nanotubes in toluene solvent and in epoxy were better than TiO 2 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 TiO 2 nanotubes with APTS improves the impact resistance and bending resistance of epoxy coating, but unchanged hardness than unmodified- TiO 2nanotubes.The obtained results shown the thermal stability of APTS-grafted TiO 2 nanotubes/ epoxy nanocomposite was higher compared

to that of the TiO 2nanotubes/ 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 energy-dispersive 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

B Contribution of the dissertation

1 Proposed process for fabricating epoxy/APTS- TiO 2 nanotubes coating to improve the corosion resistance of steel substrate

2 Proposed process for fabricating Zr/Ti/MoCC-ED coating to improve the corosion resistance of steel substrate

C Recommendations

1 The APTS- TiO 2 nanotube/epoxy coating was synthesized and researched at the Polymer Chemistry Laboratory This system should expand the application market or technology transfer On the other hand, the research of self-cleaning paint system, solar cells… should continue to invest in the future

2 The Zr/Ti/Mo conversion coating could significantly improve the corrosion protection properties of the ED coating However, the mechanism of multilayer metal deposition of Zr/Ti/Mo on steel substrate has not been studied It is necessary to study this mechanism in order to have appropriate adjustment to more improve the corrostion protection of steels

PUBLICATIONS

1 Duong Thi Hong Phan, Le Minh Duc, Dao Hung Cuong, Synthesis and mechnical properties of (3-aminopropyl triethoxysilane) grafted TiO2 – epoxy nanocomposites, Vietnam Journal of Chemistry, 4E2355, 272-277 (2017)

2.Duong Thi Hong Phan, Le Minh Duc, Dao Hung Cuong, Modification of TiO2 nanotubes with organic silane for high anticorrosion of epoxy coating, Vietnam Journal of Chemistry, 5E3455, 405-410 (2017)

3.Duong Thi Hong Phan, Le Minh Duc, Dao Hung Cuong, Protection of steel JISG 3141 with chromium-free conversion coating based on inorganic salt (Zr/Ti/Mo), Journal of Science and Technology, vol.55 (5B), 57-65 (2017)

4 Duong Thi Hong Phan, Le Minh Duc, Dao Hung Cuong, Corrosion resistance and mechanical properties of TiO2 nanotubes / epoxy coating on steel SPCC-JISG 3141, Journal of Science and Technology, vol.55 (5B), 203-209 (2017)

5 Duong Thi Hong Phan, Nguyen Tien Dung, Le Minh Duc, Dao Hung Cuong, Corrosion inhibition of steel by chromium-free conversion coating depended on inorganic (Mo/Zr/Ti), Journal of Science and Technology, The University of DaNang, 07(116), 62-

66 (2017)

6 Hong Phan Duong, Minh Duc Le, Hung Cuong Dao and Yun, Surface modification of TiO2 nanotubes by grafting with APTS coupling agents, Mater.Res.Express, Vol 4:105043, 1-9 (2017), (SCIE, IF 1.068)

Chia-7 Hong Phan Duong, Chia-Hsiang Hung, Hung Cuong Dao, Minh Duc Le and Chia-Yun Chen, Modification of TiO2 nanotubes with 3-aminopropyl triethoxysilane and its performances in nanocomposite, New J Chem, Vol.42 , 8745-8751 (2018), (SCI, IF 3.269