studies on sio2-hybrid polymeric nanocomposite … · accepted manuscript 1 studies on sio 2 -...

34
Accepted Manuscript Studies on SiO2-hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity Sh. Ammar, K. Ramesh, I.A.W. Ma, Z. Farah, B. Vengadaesvaran, S. Ramesh, A.K. Arof PII: S0257-8972(17)30617-5 DOI: doi: 10.1016/j.surfcoat.2017.06.014 Reference: SCT 22425 To appear in: Surface & Coatings Technology Received date: 5 December 2016 Revised date: 26 May 2017 Accepted date: 5 June 2017 Please cite this article as: Sh. Ammar, K. Ramesh, I.A.W. Ma, Z. Farah, B. Vengadaesvaran, S. Ramesh, A.K. Arof , Studies on SiO2-hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity, Surface & Coatings Technology (2017), doi: 10.1016/j.surfcoat.2017.06.014 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Upload: lekhuong

Post on 12-Sep-2018

219 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

Accepted Manuscript

Studies on SiO2-hybrid polymeric nanocomposite coatings withsuperior corrosion protection and hydrophobicity

Sh. Ammar, K. Ramesh, I.A.W. Ma, Z. Farah, B. Vengadaesvaran,S. Ramesh, A.K. Arof

PII: S0257-8972(17)30617-5DOI: doi: 10.1016/j.surfcoat.2017.06.014Reference: SCT 22425

To appear in: Surface & Coatings Technology

Received date: 5 December 2016Revised date: 26 May 2017Accepted date: 5 June 2017

Please cite this article as: Sh. Ammar, K. Ramesh, I.A.W. Ma, Z. Farah, B.Vengadaesvaran, S. Ramesh, A.K. Arof , Studies on SiO2-hybrid polymericnanocomposite coatings with superior corrosion protection and hydrophobicity, Surface &Coatings Technology (2017), doi: 10.1016/j.surfcoat.2017.06.014

This is a PDF file of an unedited manuscript that has been accepted for publication. Asa service to our customers we are providing this early version of the manuscript. Themanuscript will undergo copyediting, typesetting, and review of the resulting proof beforeit is published in its final form. Please note that during the production process errors maybe discovered which could affect the content, and all legal disclaimers that apply to thejournal pertain.

Page 2: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

1

Studies on SiO2 - hybrid polymeric nanocomposite coatings with

superior corrosion protection and hydrophobicity

Sh. Ammar a, K. Ramesh

a,1, I. A. W. Ma

a, Z. Farah

a, B. Vengadaesvaran

a, S.

Ramesh a, A.K. Arof

a

a Center for Ionics University of Malaya, Department of Physics, Faculty of Science,

University of Malaya, Kuala Lumpur, 50603

Abstract

Hybrid polymeric based nanocomposite coating systems (NCs) were fabricated by solution

intercalation method with the use of epoxy (E) and polydimethylsiloxane (PDMS) as the host

hybrid polymeric matrix and different weight ratio of SiO2 nanoparticles, ranging from 2 wt. %

to 8 wt. %, as the reinforcing agents. The effects of introducing PDMS as a modifier to epoxy

resin, as well as, the influence of embedding SiO2 nanoparticles within the developed matrix

were evaluated via utilizing X-ray diffraction (XRD), contact angle measurements (CA), field

emission scanning electron microscope (FESEM), and electrochemical impedance spectroscopy

(EIS). XRD and FESEM results revealed the good dispersion of the nanoparticles within the

polymeric matrix and confirmed the efficiency of the solution intercalation method. CA findings

confirmed the achievement of hydrophobic surface after modifying epoxy resin with PDMS with

CA value at 96º for epoxy- PDMS coating system (ES 0). Also CA results indicated the ability of

SiO2 nanoparticles to participate in developing more hydrophobic surface as CA value up to 132º

was achieved with utilizing 6 wt. % SiO2 loading ratio. The results obtained from EIS studies

1 Corresponding author: Tel: +60379676712; Fax: +60379674146

E-mail addresses: [email protected] (Sh. Ammar), [email protected] (K. Ramesh)

ACCEPTED MANUSCRIPT

Page 3: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

2

revealed that the coating system with 2 wt. % had the best anticorrosion performance and have

demonstrated an intact behavior over all the immersion period without any sign of coating

damage or degradation.

Keywords SiO2 nanoparticles, Anticorrosion coatings, hydrophobic surface, EIS, FESEM.

1. Introduction

Degradation of material or corrosion had been quite an issue for industries. When surfaces are

exposed to corrosive environment, degradation of materials occurs and the cost is at the

expensed of billions, both in capitals and lives [1]. X. Pei et al. have pointed out that corrosion

phenomena significantly affect the lifespan, safety, and aesthetics of the infrastructure. That in

turn leads to annual cost at approximately $276 billion just in U. S as a direct cost of metallic

corrosion. In addition, X. Pei et. also reported that Canada spends about $74 billion just to repair

the reinforced concrete structure [2].

Organic coatings are one of the promising approaches in solving the issues. Furthermore, recent

years had shown a tremendous effort in highlighting the performance of these coatings and that

includes the organic coating system and polymeric hybrid coating system that combine the both

the novelty of organic and inorganic functionalities [3-6].

Epoxy and PDMS are two different categories of polymer and both are used as coating systems

for multipurpose including anti-corrosion [5,7,8]. Despite having remarkable resistance towards

many elements, epoxy still fall short with its hydrophilic surface and weakness towards

resistance to crack propagation [9-11]. This could lead to significantly reduced barrier ability

against water, oxygen and other corrosive elements making it a poor choice for anti-corrosion

coating. PDMS on the other hand, has a superhydrophobic surfaces with poor wettability with

ACCEPTED MANUSCRIPT

Page 4: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

3

low surface energy. PDMS also possess large free volume that allows it to be used as element for

many other applications [12-14].

While the former is considered to be organic and latter, inorganic, the combination of these two

had proven to be a good anti-corrosion coating due to both properties combined together to form

a superior coating. Ammar et al. had studied the effects of intercalation of PDMS with epoxy and

revealed a significant increase of hydrophobicity of Epoxy-PDMS composite system compared

to neat epoxy [8]. Rath et al. also discovered that PDMS-modified epoxy has lower surface

energy with increases in contact angle measurement [15]. This shows that having both PDMS

and epoxy together made a better anticorrosion coating due to having intercalation of PDMS into

epoxy which lowers the surface energy and increase the hydrophobicity.

Silica or silicon dioxide, SiO2 an inorganic nanoparticle, is often used as additives to enhance the

properties of many organic base resins [16-18]. High mechanical strength, good thermal and

chemical stability and high surface area make SiO2 nanoparticles gain the trust as a useful tool to

enhance the mechanical properties and reduce its thermal degradation at high temperature of the

polymeric films [19,20]. Moreover, many researchers have confirmed the capability of SiO2

nanoparticles in enhancing the barrier properties and the hydrophobicity of the coatings system

by zigzagging the diffusion pathways against the penetrating corrosive agents and producing a

new levels of surface roughness respectively [20]. Islam et al. [17] have successfully reduced the

surface porosity of Ni–P–SiO2 nanocomposite coatings and further enhanced the corrosion

protection ability. Moreover, Pourhashem et al., [11] studied the effect of utilizing SiO2 particles

on the corrosion protection performance of the epoxy coatings via fabricating SiO2 - graphene

oxide (GO) nanohybrids via a facile one-step method. The finding of this study revealed that

utilizing SiO2 nanoparticles along with GO nanosheets led to enhance the overall performance of

ACCEPTED MANUSCRIPT

Page 5: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

4

the epoxy coatings via increasing the hydrophobicity of the resulting surface, significantly

improving the adhesion of the epoxy coating to the metallic substrate, and by giving strong

interfacial bonding with the matrix. However, homogenous mixture of silica and organic resin

are considered difficult to be achieved since the nanoparticles aggregates strongly and easily.

This is due to the H-bonding formations between the nanoparticles through the silanol group

presents at the surface [19].

In this paper, an organic-inorganic nanocomposite coating systems consisting epoxy, PDMS and

different loading rates of SiO2 nanoparticles were developed with high hydrophobicity and

superior electrochemical properties. It is worth mentioning that all reported NCs coating systems

were developed through utilizing solution intercalation method which is well documented by

Reddy [21] and Shen et al. [22]. The dispersion of the SiO2 nanoparticles within the polymeric

matrix was evaluated via using XRD and FESEM techniques. The influence of embedding SiO2

nanoparticles within the developed epoxy-PDMS hybrid polymeric matrix on the anti-corrosion

performance and on the wettability of the resulting coating systems was investigated.

2. Experimental procedures

2. 1 Materials and sample preparation

All chemicals were used as received and without any further purification. Epoxy resin

(EPIKOTE 828) representing bisphenol A and epichlorohydrin with an equivalent weight of

184–190and viscosity about 12,000–14,000 cP at 25◦C was utilized as the base and polyamide

(EPI-CURE 3125) with an amine value of 330–360 mg/g as the curing agent were both obtained

from Asachem, Malaysia. Polydimethylsiloxane-hydroxyl-terminated (PDMS) with a viscosity

of 750 cSt and density equal to 0.97 g/ml at 25◦C, used as a modifier and dibutyltindilaurate as a

ACCEPTED MANUSCRIPT

Page 6: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

5

catalyst, were both purchased from Sigma Aldrich, Malaysia. 3-Aminopropyltriethoxysilane (3-

APS), the coupling agent was obtained from Shin-Etsu Chemical Co. Ltd, Japan. Silica (SiO2)

nano-particles of 10-20 nm in diameters was obtained from Sigma Aldrich and used without any

further treatment. 90 g of the epoxy resin, 10 g of PDMS3 mL of the 3-APS, and an aliquot of

dibutyltindilaurate were mixed together in a beaker and was stirred constantly for 20 minutes at

80 ºC. Simultaneously, the nanoparticles were dissolved in xylene with weight ratio of 8:2 and

subjected to magnetic stirring at 800rpm for 30 minutes followed by 15 minutes of sonication.

Weight ratios of 2 %, 4 %, 6 % and 8 % of the dissolved SiO2 were added to the epoxy blend (ES

2, ES 4, ES 6, and ES 8, respectively) and mixed together for 20 minutes at 1000 rpm followed

by 60 minutes of sonication prior to the addition of 45 g of the polyamide curing agent. The

mixture was continuously stirred for 5 minutes followed by vacuum degassing to remove any

trapped air bubbles and additional side product (CH3OH which is a side product of the reaction

of PDMS and 3-APS).

The coating systems were applied to both-sides of cold-rolled mild steel panels (0.5 x 50.0 x 75.0

mm) which were used to perform all the tests, except for the XRD test where free films were

casted onto Teflon plates. The steel panels were cleaned using acetone and sandblasted following

the ASTM D609 standard in order to achieve Sa ½ surface profile. Single layer coatings were

applied by brush coating method and the samples were then left to dry for two days under

ambient condition and heat treated at 80 ºC for 24 hours. Elcometer 456 thickness gauge was

used to carry out thickness measurement at five different points per sample once dried. The

compositions of all prepared coating systems with their corresponding designation and the

average of the dry film thickness after been applied on the substrate surface are tabulated in

Table 1.

ACCEPTED MANUSCRIPT

Page 7: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

6

2. 2 Physical characterizations

X-ray diffraction (XRD) was run onto casted free films of roughly 2 x 2 cm per sample of the

developed coating systems. The free film samples were analyzed with High Score Plus Ver. 3.0d

(3.0.4) at diffraction angle of 2θ = 5° to 120

°. The test was done in order to study the dispersion

of the nano-particles within the coating and identify the nano-particles within the coating system.

Free flow of silica nano-particles was also run for comparison purposes. The surface morphology

and the nanoparticles dispersion within the matrix were studied through FESEM using FEI

Quanta 450 FEG at 10 kv as the accelerating voltage with the assist of low vacuum (LVSEM).

Moreover, the hydrophobicity state of the resulting coated surfaces was investigated by the

contact angle test using the OCA 15EC (data physics, Germany) instrument. Five water droplets

(5μL/drop) were dropped at five different areas on each sample using a needle located close

enough to the surface to render the kinetic energy of the droplets negligible. The image was

capture immediately to determine the static contact angle. The average of five measurements was

taken as the reported contact angle values with less than 2º measurement error.

2. 3 Electrochemical characterizations

To investigate the electrochemical behavior, anticorrosion performance and the barrier properties

of all the developed coating systems, electrochemical impedance spectroscopy (EIS) technique

was employed. A classical three-electrode cell (Shown in Fig S1) with 3 wt. % NaCl solution

was used to perform these investigations throughout 30 days of immersion. In order to develop

the electrochemical cell, a polyvinyl chloride (PVC) tube with a 2.0 cm inner diameter was

vertically fixed to the surface of the coated substrate with the help of epoxy adhesive glue. With

consideration of the adhesive joint, the sample with a 3.0 cm2 exposed area served as the

ACCEPTED MANUSCRIPT

Page 8: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

7

working electrode, a saturated calomel electrode (SCE) acted as the reference electrode, and a

platinum electrode was the counter electrode. All reported EIS studies were performed using

Gamry PC14G300 potentiostat (Gamry Instruments, Warminster, PA, USA) with a frequency

range of 100 kHz to 10 mHz run using a faraday cage, to maintain the minimum noise level

during measuring; and Echem Analyst Version 6.03 analyzer for results evaluation.

3. Results and discussion

3. 1 X-ray Diffraction (XRD)

X-ray diffraction was deployed to study the structural characterization of nano-SiO2, neat epoxy

and the hybrid nanocomposites coating free film using CuKα (λ = 1.54 Å) as the radiation

source. Braggs law equation (1) were utilized to calculate the d-spacing of relevant data

Braggs’ Law: λ = 2d sin θ (1)

Where λ = wave length, d = spacing between layers of atom and θ = angle between the incident

rays and the surface of the crystal.

Fig. 1 shows a broad peak of SiO2 spectra at 2θ = 21.9º and the peaks are compared to

JCPDS file. The d-spacing of the nanoparticles were calculated to be 4.4. The result

corresponded to the literature value (JCPDS No 47-1144) [23,24]. The diffraction pattern also

confirms all the films consist of SiO2 shows a very broad peak confirming amorphous nature.

Apart from that, the neat epoxy resin free film also shows the similar broad peak

confirming that it is also in amorphous nature. The absence of a peak at 2θ = 21.9º confirmed

there is no nano-silica powder in the epoxy resin. The ES 0 free film shows a broad peak at 2θ =

17.9º with d-spacing of 4.9 corresponds to the presence of the silicone group, Si-O-Si, from

PDMS which was blended with neat epoxy resin. This corresponds to literature value (JCPDS

ACCEPTED MANUSCRIPT

Page 9: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

8

No 27-1402) [25]. A diffraction shoulder at 2θ=12° attributes to the phenomena of PDMS

grafting the epoxy surface and the similar pattern has been observed by Ferreira et. Al [26].

However, this peak fade of when SiO2 nanoparticles were added into the hybrid solution which

leads to increase of Si-O-Si bonds. The existence of broad band at 2θ = 40 and 2θ = 50° due to

amorphous nature of the neat epoxy resin. In ES 0, this broad band shows a shift which

corresponds to the intercalation of PDMS with the epoxide group in epoxy resin. This similar

observation also has been observed in all other nanocomposite coating free films (ES 2 – ES 8)

with the incorporation of nano-silica.

Moreover, Figure 2 depicts the 2θ position and corresponding d-spacing with nano-SiO2

wt. %. The peak shift between 2θ = 19.5º and 2θ = 26.0º corresponds to the presence of nano-

silica in the form of SiO2 within the nanocomposite coatings matrices indicating intercalation of

epoxy resin penetrated the crystal plane of the nano silica [27]. The increase of d-spacing of SiO2

in ES 2 – ES 8 systems shows that the nano-silica are relatively dispersed within the matrix since

the increase of d-spacing corresponds to the increasing distance between layers of atoms. This

confirms the epoxy structure intercalates with nano-SiO2 until the lattice structure is affected.

When the loading ratio of SiO2 becomes 6 wt. %, the 2θ peak at 19.6º has shifted to a lower

value due to agglomeration of SiO2 nanoparticle and was further confirmed by the high d-

spacing of 4.5 in ES 6 as compared to ES 8 and ES 4. At the low loading ratio of 2 wt. % SiO2,

the 2θ value is observed to be low as well at 19.5º. This is due to very low loading ratio and that

the matrix could not intercalate within the plane of the nano-silica properly and this results in the

high d-spacing between the planes of silica dioxide.

3. 2 Contact angle measurement (CA)

ACCEPTED MANUSCRIPT

Page 10: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

9

In order to study the wetting ability of the coating systems, contact angle measurements were

utilized. If the contact angles measured are less than 90º, the surface is hydrophilic; if the contact

angles are between 90 º and 150

º, the surface will be classified as hydrophobic and if the angles

exceed 150 º, then the surface will be categorized as superhydrophobic surface. The values of CA

for all prepared coating systems were recorded and illustrated in Fig. 3. E 0 coating system

shows hydrophilic behavior with contact angle of 65º. As depicted in Fig. 3, the CA results

revealed that modifying neat epoxy resin with PDMS has increased the hydrophobicity of ES 0

with increasing the CA from 65º to 96

º. While, further shifting toward more hydrophobicity was

observed after the addition of 2 wt. % of SiO2 nanoparticles where ES 0 coating system shows a

tremendous increase regarding the contact angle from 96º to 122

º. The angle increases gradually

until the addition of 6 wt. % at 132º but dropped to 121

º with the application of ES 8 coating

system.

There are mainly two factors that have been recognized that can affect the wetting ability of a

coated surface. Chemical composition and surface roughness of the final system can affect the

wetting ability of the surfaces [28,29]. The effect chemical composition could be used to explain

the increased contact angle of ES 0 coating system as PDMS has naturally hydrophobic behavior

and low surface energy. Furthermore, it is an elastomer with weak intermolecular forces and the

intercalation of the PDMS into the neat epoxy affects the pre-existing surface energy of the

epoxy and thus increases the hydrophobicity of the coating [15]. In addition, introducing a

second phase to the system will increase the surface roughness and ultimately increase the

hydrophobicity of the surface coating [23]. The addition of nano silica to a coating system will

introduce a second phase dimension to the surface and roughen the surface morphology. The

increase in surface roughness affected the surface hydrophobicity through the formation of air

ACCEPTED MANUSCRIPT

Page 11: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

10

pockets between the water droplets and the surface, leading to a composite solid-liquid-air

interface system which explained the increase of contact angle for ES 2, ES 4 and ES 6.

However, the drop in ES 8 is due to the aggregation of the nano silica since it has a high

inclination to aggregate at high volume and thus affected the hydrophobicity of the surface [30].

3. 3 Morphological studies by FESEM

In order to evaluate the dispersion state of the utilized SiO2 nanoparticles within the

fabricated hybrid polymeric matrix, FESEM was utilized to analyze the surface morphology of

the coating system after been applied to the substrate surface and cured. FESEM images for all

NCs coating systems were depicted in Fig. 4 (a) – (d). Besides investigating the nanoparticles

distribution within the surface area, the surface properties and phase distribution can be

evaluated via FESEM technique. From the obtained micrographs, an acceptable dispersion of

SiO2 nanoparticles within the hybrid polymeric matrix could be confirmed without any presence

of cracks or phase separation. Furthermore, it was interesting to notice that as the incorporation

of SiO2 nanoparticles resulted in achieving higher values of CA and developing surfaces that

characterized with more hydrophobicity. FESEM images of All NCs have revealed a good

dispersion of the nanoparticles which could ensure the creation of more rough surface with

heterogeneous morphology which was found in strong agreement with CA results.

Moreover, FESEM findings could obtain an evidence regarding the competence of the

sonication process in developing a good level nanoparticles dispersion within the polymeric

matrix. Under the same conditions of the sonication process, increasing the loading ratio of the

nanoparticles resulted in increasing the amount of the nanoparticles in the area unit. Hence, the

ability of the particles to be attracted to each other enlarged, thus producing relatively larger

agglomerated particles. It was clearly observed that ES 6 coating system demonstrated the best

ACCEPTED MANUSCRIPT

Page 12: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

11

nanoparticles distribution which could revealed that 6 wt. % of SiO2 could be considered the

optimum loading ration that can ensure that the nanoparticles can cover all the surface area

without forming large agglomerated particles. In fact, it is worth to be mentioned that there are

many parameters involving in determining the optimum loading ratio of the nanoparticles for the

coating system (i.e. particles size, sonication time, sonication power). However, increasing the

loading ratio of the SiO2 nanoparticles up to 8 wt. % led to observe some agglomerations of the

nanoparticles as depicted in Fig. 4 (c) and (d). That can be explained by the fact that the distance

between the nanoparticles become smaller as the number of the particles increases within the

area unit and also due to the tendency of the nanoparticle to agglomerate at the high loading rates

[30,31].

3. 4 Electrochemical impedance spectroscopy (EIS)

The EIS measurements were conducted periodically (every five days) after exposure to 3% NaCl

solution and the results were expressed graphically using Nyquist and Bode plots as illustrated in

Fig. 5 and 6 after 1 and 30 days of immersion time, respectively. According to the

electrochemical behavior of the various prepared coating systems, three different models of the

equivalent circuit were proposed in the regard of obtaining the best numerical fitting along all

study periods. From Fig. 5 it can be seen that along all prepared coating systems, just the neat

epoxy, E 0, coating system has demonstrated a sign of electrolyte penetration initiation as a full

semi-circle observed in the Nyquist plot and an obvious bend in the low-frequency region with

Bode plot. This observation further confirms the fact that pure organic resins cannot behave as

intact coating layers with superior barrier performance due to the existence of free volume and

ACCEPTED MANUSCRIPT

Page 13: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

12

porosity which directly act as a diffusion pathway for the electrolyte toward the coating - metal

interface [32,33]. At this stage of immersion, model B of the equivalent circuit perfectly describe

the electrochemical behavior of E 0 coating system. This model consists of the following

elements: a resistor Rs, solution resistance, which does not have any important technical or

theoretical information about the coating system thus was not included in this study [33]. A

resistor Rpo and a constant phase element CPEpo which represents the electrolyte resistance

through the pores, and its associated CPEpo. In addition, this model contains a parallel

combination of a constant phase element and resistor which in turn represent the parameters of

the corrosion reaction namely, constant phase element of double layer capacitance (CPEdl) and

charge transfer resistance (Rct). However, in contrary, ES 0 and all prepared NCs demonstrated a

capacitive behavior with one capacitive loop in Nyquist plot and straight line in the Bode plot

with a slope of -1 which is a clear evidence about the efficiency of these coating systems in

preventing any penetration of the electrolyte with complete isolation of the metal surface from

the surrounding corrosion medium. As there was no any charge transfer or diffusion of the

electrolyte within the coating films, model A with just Rs, Rpo and CPEpo were used to fit the EIS

diagrams at this stage of immersion time.

As the exposure time elapsed, the most significant degradation was found with the substrate

coated with a E 0 coating system. As illustrated in Fig. 6, two full semi-circuit in Nyquist plot

with Bode plot of two times constant which indicate the poor corrosion resistance of the epoxy

resin. As the penetration of the 3% NaCl solution leads to initiate the corrosion process, model C

of the equivalent circuit with new components namely, constant phase element of diffusion

capacitance (Cdiff) and diffusion resistance (Rdiff), was suggested in order to describe the

diffusion process of the corrosion products within the coating film.

ACCEPTED MANUSCRIPT

Page 14: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

13

On the other hand, the incorporation of PDMS with the epoxy resin results in a remarkable

enhancement in the anti-corrosion performance as the EIS results of the ES 0, after 30 days of

immersion, were found with one semi-circle in Nyquist plot and Bode plot with one time

constant as the straight line bend in the low-frequency region. However, this observation

revealed the ability of PDMS in enhancing the corrosion protection performance which was in

accordance with the findings reported in the literature [8,34,35]. However, as the impedance

plots of ES 0 coating system were demonstrated one time constant and been fitted with model B

of the equivalent circuit, it can be understood that even the hybrid polymeric matrix could suffer

a degradation of the barrier properties after long time of immersion and demonstrate a limitation

in performing as intact coating film against corrosion. Among all prepared NCs coating systems,

ES 2 system with 2 wt. % SiO2 nanoparticles demonstrated the best performance with almost no

changes observed with Nyquist and Bode plot with one capacitive loop in Nyquist plot and a

straight line in the Bode plot with a slope of -1 which represent the total capacitive behavior of

the coating film. This is due to the effective barrier role of the nano-sized SiO2 particles within

the hybrid polymeric matrix which led to close up the pores and zigzag the diffusion pathways

against the corrosive agents. That, in turn, force these agents to travel longer distance to reach

the substrate, therefore, gaining more stability against corrosion [30,36]. It is worth mentioning

that no further protection was developed as the SiO2 loading ratio increased up to 4 wt. %.

However, as higher loading ratio of the SiO2 nanoparticles utilized up to 8 wt. %, the corrosion

properties of the coating systems declined. As a full semi-circle observed in the Nyquist plot and

an obvious bend in the low-frequency region with Bode plot were observed with ES 6 and ES 8

coating systems. That could be attributed to the tendency of the nanoparticles to form

agglomerations at the high loading ratio as the number of the nanoparticles increases within the

ACCEPTED MANUSCRIPT

Page 15: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

14

unit area. Thus forming a larger particles size will affect the barrier properties of the utilized

reinforcing particles will face some difficulties in achieving the will dispersion within the

polymeric matrix and fill up all the pores. Moreover, all the values of all parameters that have

been obtained by fitting the EIS data according to the proposed equivalent circuit models after 1

day and 30 days of immersion are tabulated in Tables S 1 and S 2 in Supplementary material.

Investigating the stability of the coating films against been damaged by the electrolyte and

evaluate the state of the interfacial adhesion bonds at the coating - substrate interface over the

different immersion periods were carried out via using EIS method in the Bode plot format

(impedance and phase angle as a function of the frequency). With the assist of breakpoint

frequency values, which is the frequency at - 45º phase angle, the region below the Bode plot

could be divided into capacitive and resistive regions. After that, recording and analyzing the

changes that could happen to these regions for each coating system over the whole period of

immersion could help to obtained full understanding and detailed information about the

electrochemical behavior, barrier properties, coating delamination and electrolyte diffusion state

[37,38]. Fig. 8 (a) and (b) illustrate the Bode plots of E 0 coating system after 1 and 30 days of

immersion, respectively. As it can be clearly seen that E 0 coating system demonstrated two

regions under the Bode plot since the first day of immersion namely, a resistive region at low-

frequency domain and a capacitive region at high-frequency domain. However, after 30 days of

immersion, an increase with the resistive region and corresponded decrease in the capacitive

region indicate the diffusion of the electrolyte within the coating film, thus, coating delamination

and loss of adhesion occurred at the substrate surface. In contrary, as it can be clearly observed

in Fig. 9 (a) and (b), that showing the Bode plots of ES 0 coating system after 1 and 30 days of

immersion, respectively, the incorporation of PDMS within the epoxy resin results in enhancing

ACCEPTED MANUSCRIPT

Page 16: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

15

the barrier properties as lower breakpoint frequency was recorded, therefore, a relatively smaller

resistive region at the low-frequency domain and larger capacitive region among the neat epoxy

coating system was recorded.

However, the efficiency of utilizing SiO2 nanoparticles to enhance the corrosion protection

performance and obtain more stability against the exposure to the electrolyte was confirmed by

plotting the Bode plots after 1 and 30 days of immersion as shown in Fig. 10 (a) and (b),

respectively. A capacitive behavior over the whole tested frequency ranges indicated the

superiority of ES 2 coating system in acting as intact coating film without any damage or

electrolyte penetration up to 30 days of immersion.

Moreover, coating damage index which as a good indicator to study the integrity of the coating

systems was obtained from EIS studies and was used to classify the developed coating system

and confirm the ability of SiO2 nanoparticles to guarantee the development of intact organic-

based coating system. Coating damage index (D2) and could be obtained from the following

equation [37]:

𝐷2 = (𝐴2

𝐴1) × 100 (2)

Where A1 is the area of the capacitive region and A2 is the area of the resistive region. Fig. 11

illustrates the coating damage index of all prepared coating systems after 1 day and 30 days of

immersion. The highest coating damage was recorded for neat epoxy coating system, E 0, after 1

day of immersion. As PDMS was incorporated within epoxy resin, lower damage index was

achieved. However, no damage was observed for all NCs coating systems at this stage of

immersion. After 30 days of immersion, all prepared coating systems showed a damage at

different levels except ES 2 coating system which demonstrated a superior intact behavior and

ACCEPTED MANUSCRIPT

Page 17: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

16

completely prohibited the corrosive agent and the electrolyte to be penetrated within the

polymeric matrix and reach the substrate surface.

4. Conclusions

Neat epoxy and hybrid epoxy - PDMS coatings were successfully fabricated and investigated.

After that, the developed hybrid polymeric blend was utilized as the host matrix and has

reinforced with four different weight rates of SiO2 nanoparticles. The development of these

nanocomposite coating systems was carried out through the employment of solution intercalation

method with the assistance of sonication process. The integrity of introducing the inorganic nano

fillers, the achievement of good dispersion and the resultant morphology were examined via

XRD and FESEM techniques. The water repellence of the developed coated surface was

evaluated by CA measurements. Moreover, EIS studies were carried out up to 30 days of

immersion in 3% NaCl solution to investigate the corrosion protection performance and the

barrier properties of all developed coating systems. Furthermore, with the excellent intercalated

structure of the nanocomposite coating evinced on the ability of the incorporated nano SiO2

nanoparticles to alter the overall coating performance through forming a hydrophobic character

with superior barrier properties was obtained via CA and EIS findings. FESEM images revealed

good dispersion of the nanoparticles at low loading rates and giving a sign about the initiation of

agglomerations as the loading ratio of SiO2 nanoparticles exceed 6 wt. %. EIS studies revealed

that after 30 days of immersion time the best anticorrosion properties were observed for ES 2

coating system with significant stability over the entire immersion time. Besides, the

investigation on the damage index further confirmed the superior intact behavior of this system

which loaded with 2 wt. % nano SiO2.

ACCEPTED MANUSCRIPT

Page 18: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

17

Acknowledgement

We would like to thank University of Malaya for supporting this project with the grants PG001 –

2016A and BKS027-2017. We also thank Ministry of Education for the FRGS grant FP12-

2015A.

References

[1] A. Popoola, O.E. Olorunniwo, O.O. Ige, Corrosion resistance through the application of anti-

corrosion coatings, in: M.Aliofkhazraei (Ed.), Developments in Corrosion Protection, Intech,

Pretoria, South Africa, (2014) 241-270.

[2] X. Pei, M. Noël, M. Green, A. Fam, G. Shier, Cementitious coatings for improved corrosion

resistance of steel reinforcement, Surf. Coat. Technol., 315 (2017) 188-195.

[3] S. Ammar, K. Ramesh, N. A. Noor Azman, B. Vengadaesvaran, S. Ramesh, A. Arof,

Comparison studies on the anticorrosion and overall performance of solvent/ water based epoxy -

copper reinforced composite coatings, Mater. express, 6 (2016) 403-413.

[4] V. Dalmoro, J.H.Z. dos Santos, E. Armelin, C. Alemán, D.S. Azambuja, Phosphonic

acid/silica-based films: A potential treatment for corrosion protection, Corros. Sci., 60 (2012)

173-180.

[5] I.A.W. Ma, A. Shafaamri, R. Kasi, F.N. Zaini, V. Balakrishnan, R. Subramaniam, A.K. Arof,

Anticorrosion Properties of Epoxy/Nanocellulose Nanocomposite Coating, BioResources, 12

(2017) 2912-2929.

[6] N. Karthik, M.G. Sethuraman, Improved copper corrosion resistance of epoxy-functionalized

hybrid sol–gel monolayers by thiosemicarbazide, Ionics, 21 (2015) 1477-1488.

[7] T. Zhou, X. Wang, P. Cheng, T. Wang, D. Xiong, Improving the thermal conductivity of

epoxy resin by the addition of a mixture of graphite nanoplatelets and silicon carbide

microparticles, Express Polym. Lett., 7 (2013) 585-594.

[8] S. Ammar, K. Ramesh, B. Vengadaesvaran, S. Ramesh, A. Arof, Amelioration of

anticorrosion and hydrophobic properties of epoxy/PDMS composite coatings containing nano

ZnO particles, Prog. Org. Coat., 92 (2016) 54-65.

[9] M. Bagherzadeh, T. Mousavinejad, Preparation and investigation of anticorrosion properties

of the water-based epoxy-clay nanocoating modified by Na+-MMT and Cloisite 30B, Prog. Org.

Coat., 74 (2012) 589-595.

ACCEPTED MANUSCRIPT

Page 19: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

18

[10] E. Huttunen-Saarivirta, G. Vaganov, V. Yudin, J. Vuorinen, Characterization and corrosion

protection properties of epoxy powder coatings containing nanoclays, Prog. Org. Coat., 76

(2013) 757-767.

[11] S. Pourhashem, M.R. Vaezi, A. Rashidi, Investigating the effect of SiO2 -graphene oxide

hybrid as inorganic nanofiller on corrosion protection properties of epoxy coatings, Surf. Coat.

Technol., 311 (2017) 282–294.

[12] A. Cholewinski, J. Trinidad, B. McDonald, B. Zhao, Bio-inspired polydimethylsiloxane-

functionalized silica particles-epoxy bilayer as a robust superhydrophobic surface coating, Surf.

Coat. Technol., 254 (2014) 230-237.

[13] C.-H. Xue, M. Li, X.-J. Guo, X. Li, Q.-F. An, S.-T. Jia, Fabrication of superhydrophobic

textiles with high water pressure resistance, Surf. Coat. Technol., 310 (2017) 134-142.

[14] C. Cai, N. Sang, S. Teng, Z. Shen, J. Guo, X. Zhao, Z. Guo, Superhydrophobic surface

fabricated by spraying hydrophobic R974 nanoparticles and the drag reduction in water, Surf.

Coat. Technol., 307 (2016) 366-373

[15] S. Rath, J. Chavan, S. Sasane, A. Srivastava, M. Patri, A. Samui, B. Chakraborty, S.N.

Sawant, Coatings of PDMS-modified epoxy via urethane linkage: Segmental correlation length,

phase morphology, thermomechanical and surface behavior, Prog. Org. Coat., 65 (2009) 366-

374.

[16] S. Kasturibai, G.P. Kalaignan, Physical and electrochemical characterizations of Ni-SiO2

nanocomposite coatings, Ionics, 19 (2013) 763-770.

[17] M. Islam, M.R. Azhar, N. Fredj, T.D. Burleigh, O.R. Oloyede, A.A. Almajid, S.I. Shah,

Influence of SiO 2 nanoparticles on hardness and corrosion resistance of electroless Ni–P

coatings, Surf. Coat. Technol., 261 (2015) 141-148.

[18] M. Zhao, X. Zuo, C. Wang, X. Xiao, J. Liu, J. Nan, Preparation and performance of the

polyethylene-supported polyvinylidene fluoride/cellulose acetate butyrate/nano-SiO2 particles

blended gel polymer electrolyte, Ionics, 22 (2016) 2123-2132.

[19] T. Ribeiro, C. Baleizão, J.P.S. Farinha, Functional films from silica/polymer nanoparticles,

Materials, 7 (2014) 3881-3900.

[20] S.S. Ray, M. Okamoto, Polymer/layered silicate nanocomposites: a review from preparation

to processing, Prog. Polym. Sci., 28 (2003) 1539-1641.

[21] B. Reddy, Advances in diverse industrial applications of nanocomposites, Intech, (2011)

113-139.

[22] Z. Shen, G.P. Simon, Y.-B. Cheng, Comparison of solution intercalation and melt

intercalation of polymer–clay nanocomposites, Polymer, 43 (2002) 4251-4260.

ACCEPTED MANUSCRIPT

Page 20: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

19

[23] S. Palraj, M. Selvaraj, K. Maruthan, G. Rajagopal, Corrosion and wear resistance behavior

of nano-silica epoxy composite coatings, Prog. Org. Coat., 81 (2015) 132-139.

[24] G. Nallathambi, T. Ramachandran, V. Rajendran, R. Palanivelu, Effect of silica

nanoparticles and BTCA on physical properties of cotton fabrics, Mater. Res., 14 (2011) 552-

559.

[25] A. Kabra, P. Mahanwar, V. Shertukde, V. Bambole, Performance of nanosilica in acrylic

polyol 2K polyurethane coatings, Pigm. Resin. Technol., 41 (2012) 230-239.

[26] P. Ferreira, Á. Carvalho, T.R. Correia, B.P. Antunes, I.J. Correia, P. Alves,

Functionalization of polydimethylsiloxane membranes to be used in the production of voice

prostheses, Science and Technology of Advanced Materials, 14 (2013) 055006.

[27] S. Chandrasekaran, M.J. Sweetman, K. Kant, W. Skinner, D. Losic, T. Nann, N.H.

Voelcker, Silicon diatom frustules as nanostructured photoelectrodes, Chem. Commun., 50

(2014) 10441-10444.

[28] S. Wang, Y. Li, X. Fei, M. Sun, C. Zhang, Y. Li, Q. Yang, X. Hong, Preparation of a

durable superhydrophobic membrane by electrospinning poly (vinylidene fluoride)(PVDF)

mixed with epoxy–siloxane modified SiO2 nanoparticles: a possible route to superhydrophobic

surfaces with low water sliding angle and high water contact angle, J. Colloid Interface Sci., 359

(2011) 380-388.

[29] L. Jiang, R. Wang, B. Yang, T. Li, D. Tryk, A. Fujishima, K. Hashimoto, D. Zhu, Binary

cooperative complementary nanoscale interfacial materials, Pure Appl. Chem., 72 (2000) 73-81.

[30] B. Ramezanzadeh, M. Attar, M. Farzam, A study on the anticorrosion performance of the

epoxy–polyamide nanocomposites containing ZnO nanoparticles, Prog. Org. Coat., 72 (2011)

410-422.

[31] S. Ammar, K. Ramesh, B. Vengadaesvaran, S. Ramesh, A. Arof, Formulation and

characterization of hybrid polymeric/ZnO nanocomposite coatings with remarkable anti-

corrosion and hydrophobic characteristics, J. Coat. Technol. Res., 13 (2016) 921-930.

[32] S. Ammar, K. Ramesh, B. Vengadaesvaran, S. Ramesh, A. Arof, A novel coating material

that uses nano-sized SiO2 particles to intensify hydrophobicity and corrosion protection

properties, Electrochim. Acta, 220 (2016) 417-426.

[33] C. Zhou, X. Lu, Z. Xin, J. Liu, Y. Zhang, Polybenzoxazine/SiO2 nanocomposite coatings for

corrosion protection of mild steel, Corros. Sci., 80 (2014) 269-275.

[34] S.A. Kumar, T. Balakrishnan, M. Alagar, Z. Denchev, Development and characterization of

silicone/phosphorus modified epoxy materials and their application as anticorrosion and

antifouling coatings, Prog. Org. Coat., 55 (2006) 207-217.

[35] D. Duraibabu, T. Ganeshbabu, R. Manjumeena, P. Dasan, Unique coating formulation for

corrosion and microbial prevention of mild steel, Prog. Org. Coat., 77 (2014) 657-664.

ACCEPTED MANUSCRIPT

Page 21: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

20

[36] X. Yuan, Z. Yue, X. Chen, S. Wen, L. Li, T. Feng, EIS study of effective capacitance and

water uptake behaviors of silicone-epoxy hybrid coatings on mild steel, Prog. Org. Coat., 86

(2015) 41-48.

[37] B. Ramezanzadeh, S. Niroumandrad, A. Ahmadi, M. Mahdavian, M.M. Moghadam,

Enhancement of barrier and corrosion protection performance of an epoxy coating through wet

transfer of amino functionalized graphene oxide, Corros. Sci., 103 (2016) 283-304.

[38] E. Ghasemi, B. Ramezanzadeh, S. Saket, S. Ashhari, Electrochemical investigation of the

epoxy nanocomposites containing MnAl2O4 and CoAl2O4 nanopigments applied on the

aluminum alloy 1050, J. Coat. Technol. Res., 13 (2016) 97-114.

ACCEPTED MANUSCRIPT

Page 22: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

21

Table 1: Composition and nomenclature of all prepared coating systems

System Epoxy wt. % PDMS wt. % Nano SiO2 wt.

%

Code Dry film

thickness

1 100.0 0.0 0.0 E 0 71.2 ± 3.2

2 90.0 10.0 0.0 ES 0 73.4 ± 1.7

3 90.0 10.0 2.0 ES 2 72.0 ± 2.5

4 90.0 10.0 4.0 ES 4 71.9 ± 2.6

5 90.0 10.0 6.0 ES 6 74.3 ± 1.9

6 90.0 10.0 8.0 ES 8 71.1 ± 3.7

ACCEPTED MANUSCRIPT

Page 23: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

22

Fig. 1. XRD patterns of nano-SiO2, neat epoxy and nanocomposites coating systems

Fig. 2. The peak position of 2θ and respective d-spacing of NCs coating (ES 0 – ES 8)

Fig. 3. Representative the contact angle values of all prepared coating systems

Fig. 4: FESEM images of (a) ES 2, (b) ES 4, (c) ES 6 and (d) ES 8 nanocomposite coating

systems

Fig. 5. Representative (a) Nyquist and (b) Bode plots for all prepared coating systems after 1 day

of immersion.

Fig. 6. Representative (a) Nyquist and (b) Bode plots for all prepared coating systems after 30

days of immersion.

Fig. 7. Representative Bode plots of E 0 coating system after a) 1 day and b) 30 days of

immersion along with the determining the breakpoint frequency and the correspond capacitive

(A1) and resistive (A2) regions.

Fig. 8. Representative Bode plots of ES 0 coating system after a) 1 day and b) 30 days of

immersion along with the determining the breakpoint frequency and the correspond capacitive

(A1) and resistive (A2) regions.

Fig. 9. Representative Bode plots of ES 2 coating system after a) 1 day and b) 30 days of

immersion along with the determining the breakpoint frequency and the correspond capacitive

(A1) and resistive (A2) regions.

Fig. 10. Coating damage index of all prepared coating systems after 1 and 30 days of immersion.

ACCEPTED MANUSCRIPT

Page 24: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

23

Fig. 1.

ACCEPTED MANUSCRIPT

Page 25: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

24

Fig. 2.

ACCEPTED MANUSCRIPT

Page 26: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

25

Fig. 3.

ACCEPTED MANUSCRIPT

Page 27: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

26

Fig. 4.

ACCEPTED MANUSCRIPT

Page 28: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

27

Fig. 5.

ACCEPTED MANUSCRIPT

Page 29: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

28

Fig. 6.

ACCEPTED MANUSCRIPT

Page 30: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

29

Fig. 7.

ACCEPTED MANUSCRIPT

Page 31: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

30

Fig. 8.

ACCEPTED MANUSCRIPT

Page 32: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

31

Fig. 9.

ACCEPTED MANUSCRIPT

Page 33: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

32

Fig. 10.

ACCEPTED MANUSCRIPT

Page 34: Studies on SiO2-hybrid polymeric nanocomposite … · ACCEPTED MANUSCRIPT 1 Studies on SiO 2 - hybrid polymeric nanocomposite coatings with superior corrosion protection and hydrophobicity

ACCEP

TED M

ANUSC

RIPT

33

Highlights

1. Nano silica reinforced epoxy/PDMS hybrid coatings were developed.

2. Contact angle has been improved from 65o to 132o.

3. The lowest coating damage index exhibited by coatings with 2 wt.% SiO2 nanoparticles.

ACCEPTED MANUSCRIPT