João Tedim University of Aveiro, Portugal

2010 INTERNATIONAL WORKSHOP ON ENVIRONMENT AND ENERGY

San Diego, California November 2 - 4, 2010

Synthesis and characterization of functional Synthesis and characterization of functional nanocontainers for active corrosion protectionnanocontainers for active corrosion protection

João TedimJoão TedimUniversity of Aveiro, Portugal

2-4 November 2010 WORKSHOP ON ENVIRONMENT AND ENERGY

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Direct incorporation of corrosion inhibitors in coating formulations can lead to several problems:

-detrimental interaction between inhibitors and coating matrix (technical)

-constant/spontaneous leaching of inhibitors into the environment (environmental and economical)

Limitation of the coating protective Limitation of the coating protective action in time and magnitudeaction in time and magnitude

1. Introduction


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Aggressive species

Corrosion products

Protective film

Metallic substrate

CoatingNanocontainer

Corrosion inhibitor

CorrosionSolution Encapsulation/intercalation of corrosion inhibitors in nanocontainers capable of release-on-demand

Protection!Protection!


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Micro/nanocontainer + Corrosion inhibitor >= Chromates

Inert, hosting structures

Release mechanisms

Active protection

Low toxicity

Types of containers:

-inorganic, organic, hybrid

Release mechanisms:

-mechanical impact

-pH -H2O

-presence of aggressive species (e.g. chlorides)

Potential advantages related to this strategy:

• improvement of coating integrity

• smaller amounts of inhibitor required

• development of new value-added products

• comply with environmental law regulations


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Layered double hydroxides (LDHs)

Applications:

Sorbents, Drug-delivery systems, Polymer stabilizers, Heterogeneous catalysis

H2O

An- An- An-H2O

An- An- An-

[M2+1-xM3+

x(OH)2]An-x/n·mH2O

Silica nanocapsules (SiO2)

Applications:

Drug-delivery systems

Transport carriers

Nano-reactors


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2. Experimental• Synthesis of LDHs-methodologies applied: ion-exchange, calcination-rehydration-corrosion inhibitors intercalated: MoO4

2-, VO3-, MBT

• Synthesis of SiO2

-oil-in-water microemulsion-corrosion inhibitor: MBT

• Structural/morphological characterizationXRD, SEM, TEM• Release studies HLPC

•Corrosion studies EIS


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3. Struture and morphology

10 20 30 40 50 60

Inte

nsi

ty/(

a.u

.)

2/degrees

LDH-NO3

LDH-VOx

LDH-MoO4

LDH-MBT

003

006

LDH-NO3 LDH-VOx

•Plate-like morphology

• LDH particles: 200-400 nm diameter and 20-40 nm height

•Peak positions at low angles: information on the gallery height (anion size

and orientation)

XRD SEM

TEM

LDHsLDHs


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FTIR XRD TEM

•Porous, spherical particles 150 nm diameter

•Different core/shell porosities

SEM

SiOSiO22


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4. Release studies-LDHs

•The release of NOThe release of NO33-- and MoO and MoO44

2-2- anions is triggered by the anions is triggered by the presence of chloride anionspresence of chloride anions

0 100 200 300 400 500 600 700 8000

100

200

300

400

500 mM NaCl

50 mM NaCl

Mo

O2

-

4 r

ele

as

e/m

gL

-1

Time / min

NaCl distilled water

5 mM NaCl

0 100 200 300 400 500 600 700 800

200

300

400

500

600

700

800

900

NO

- 3 r

ele

ase

/mg

L-1

Time / min

NaCl distilled water

5 mM NaCl

50 mM NaCl

500 mM NaCl


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SH-MBTSH-MBT Zn(2)-Al-MBTZn(2)-Al-MBT

•Two release profiles are observed: short (1-2h) and long Two release profiles are observed: short (1-2h) and long timescales (>100 h)timescales (>100 h)

•Profile at short timescales is not sensitive to the Profile at short timescales is not sensitive to the concentration of Clconcentration of Cl--

0.01 0.1 1 10 100 100050

100

150

200

250

300

350

400

450

II

|MB

T| re

leas

ed/m

g L

-1

Time/hours

0.005 M NaCl 0.05 M NaCl 0.5 M NaCl

I

0.1 1 10 1000

100

200

300

400

500

600

II

|MB

T| re

leas

ed/m

g L

-1

Time/hours

0.005 M NaCl 0.05 M NaCl 0.5M NaCl

I


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4. Release studies-SiO2

•MBT released preferentially in concentrated MBT released preferentially in concentrated NaCl solutions and acidic conditionsNaCl solutions and acidic conditions


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5. Assessment of anticorrosion performance-EIS

10-2 10-1 100 101 102 103 104 10520

0

-20

-40

-60

-80

0.05 M NaCl LDH-NO

3

LDH-VOx

LDH-MoO4

Phas

e an

gle

/ deg

rees

Frequency/Hz

10-2 10-1 100 101 102 103 104 105

102

103

104

105 0.05 M NaCl LDH-NO

3

LDH-VOx

LDH-MoO4

|Z|/

cm2

10-2 10-1 100 101 102 103 104 105200

-20-40-60-80

-100 Bare metal SiO

2

SiO2-MBT

|Z|/

.cm

2

Frequency/Hz

1 day

10-2 10-1 100 101 102 103 104 105

102

103

104

105

106

Bare metal SiO

2

SiO2-MBT

Phas

e an

gle/

Deg

rees

Frequency/Hz

•EIS spectra for bare AA2024 after 1 day of immersion in 0.05 M NaCl


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10-2 10-1 100 101 102 103 104 105

102

103

104

105

106 Bare metal SiO

2

SiO2-MBT

|Z|/.

cm2

Frequency/Hz

1 month

10-2 10-1 100 101 102 103 104 105

0

-20

-40

-60

-80

-100

Pha

se a

ngle

/Deg

rees SiO2 SiO2-MBT

1 month of immersion in 0.05 M NaCl

•The presence of inhibitor determines the (active) protection of the metal substrate


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Concluding Remarks

• LDH nanocontainers and SiO2 nanocapsules were synthesized

and corrosion inhibitors successfully intercalated/

encapsulated• Release studies showed that the optimal conditions for the

release of corrosion inhibitors are

-LDHs (NaCl) -SiO2 (pH and NaCl)

• The anticorrosion activity in solution depends on the strength

of the inhibitor


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Future perspectives

• Incorporation of corrosion inhibitor/nanocontainer ‘pigments’ in coating formulations from aeronautical, automotive and maritime industry

-dispersion optimization via surface modification -assessment of the protection performance of the coatings

• Optimization of the nanocontainers for specific applications -action on the release response -screening of inhibitors, combination of inhibitors displaying

synergistic effects


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Acknowledgments• Miss Alena Kuznetsova• Mr Frederico Maia• Dr Andrei Salak• Dr Mikhail Zheludkevich• Prof Mário G. S. Ferreira

European project MUST ref. NMP3-LA-2008-214261

Documents

João Tedim University of Aveiro, Portugal