Dowsett, M. Electrochemical Study Coatings Protection and Inhibition. 2010

8/7/2019 Dowsett, M. Electrochemical Study Coatings Protection and Inhibition. 2010

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Spectro-electrochemical study of the growth of lead

carboxylate coatings for corrosion protection and

inhibition

aMark Dowsett, bAnnemie Adriaens

aDepartment of Physics, University of Warwick, UKbDepartment of Analytical Chemistry, Ghent University, Belgium

[email protected] , [email protected]

International workshop and training school on Electrochemistry in Historical andArchaeological Conservation, Lorentz Centre, Leiden, Jan 11-15, 2010


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Acknowledgements

Students:Alice Elia, Arie Papot, Gareth Jones, Karen Leyssens, Bart

Schotte

Beam line scientists:Laurence Bouchenoire, Chris Martin

Technical support:

Adrian Lovejoy, Derrick Richards, Pieter van Hoe

Funding:

Paul Instrument Fund, EVA Surface Analysis, FWO


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Protective coating

Characteristics

stable

reversible or easy to remove

protective against corrosion

sthetically justified

Lead Carboxylates*

easy to apply and inexpensive (even numbered C chains used in

food and cosmetics) removed by water or ethanol

almost invisible (slight darkening c.f. new lead) when thin

how protective against corrosion?

*Rocca, E.; Steinmetz, J. Cor. Sci. 2001, 43, 891-902


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Application of a lead carboxylate coating(e.g. lead decanoate)*

Immerse sample in 0.05 M sodium decanoateCH3(CH2)8COONa solution (NaC10)for several hours

Protection increases with carboxylate chain length,solubility decreases.

Pb(C10)2 a good compromise?

(Thus far, and no farther in aqueous solution.)

Courtesy Carl Johan Bergstein


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Evaluation using simultaneous time resolvedSR-XRD and electrochemical methods in eCell

eCell

- efor electrochemistrye.g. Electrochemical ImpedanceSpectroscopy (EIS)Open Circuit Potential (OCP)

- efor environment

Monitor growth of layer in real time

Evaluate corrosion inhibitionin acetic acid vapour/air mixture

Counterelectrode

Piston

Workingelectrodeassembly

Cam

Wiring to

workingelectrode

Referenceelectrode


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eCell mounted on beamline BM28(XMaS) at the ESRF

Ideal combination of beamintensity and acquisition speedfor sensitivity and timeresolution

2-D Mar camera (detector)

Open beam-linegeometry/Huber goniometerallows experiments to beextended to whole artefacts in

future


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Lead Carboxylate - Growth

Ex 23 XMaS March2006 10 min cycle


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Lead Carboxylate - Growth

Ex 23 XMaS March2006 10 min cyclegrowth time / h

0 1 2 3 4 5 6

Intensity/Arb.units

0.0

0.1

0.2

Pb(C10)2 (7.64)

Pb(C10)2 (6.11)

Pb(2.855)

Pb(C10)2 (3.99)

Pb(C10)2 (4.87)

PbO (3.115)


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Open circuit potential as a function of time

time / h

0 2 4 6 8

OCP/(Vvs

Ag/AgCl)

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4


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0 2 4 6 8 10

0

2

4

6

8

0.17 h

1.17 h2.17 h

3.17 h

4.17 h

5.17 h

6.17 h

Real impedance / (k.cm2)

Imaginaryim

pedance/(k.cm

2)

Interleaved EIS as a function of time

RL

RsCL

Re(Z)/(Mcm2)

0.000 0.002 0.004 0.006 0.008 0.010 0.012

-Im

(Z)/(Mcm2)

0.000

0.002

0.004

0.006

0.008

0.010

0.012

Model Parameters: Electrolyte resistance 420

Layer resistivity 3.8 x 108 cm

Starting thickness 0.3 nm

Growth rate 9 nm min-1

CPE 69 Ss

-0.52

RL

RsCPEL


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Real impedance/(Mcm2)0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

0.0

0.2

0.4

0.6

0.8

1.0

1 h

2 h

3 h

4 h

5 h

6 h

0.000 0.005 0.0100.0000

0.0005

0.0010

0.0015

0.0020

0.00250.0030

0 h

0.01

Imaginaryimpedance/(Mcm2)

EIS as a function of time (good layer)

Re(Z)/(Mcm2)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

-Im(Z)/(Mcm

2)

0.0

0.2

0.4

0.6

0.8

1.0

1 h

2 h

3 h

4 h

5 h6 h

0.00 0.010.000

0.001

0.002

0.003

0.004

0 h

1000 Hz 1 Hz 0.1 Hz

1 75 81pointnumber

Model Parameters: Electrolyte resistance 100 cm2

Layer resistivity 1.04 x 1010 cm

Starting thickness 0.3 nm

Growth rate 6 nm min-1

CPE 550 Ss

-0.85

RL

RsCPEL


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SEM

1 h0 h

2 h 6 h


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Evaluating the protection

2.5 L glacial acetic acid in 30 mL air in eCell

6.6% by mass (3.3% by molecular density)

Saturated NaCl solution for 75% RH

+

Apply to bare and coated lead in eCell


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1.67 h

8.16 hEx 17 XMaS Dec2006 20 min cycle

Bare Lead 2- Acetic atmosphere (6.6%) w/w


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7 h

Ex 13 XMaS Dec2006 30 min cycle

Protected Lead - Acetic atmosphere (6.6%) w/w


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Growth from carboxylic acid in ethanol

0.1 M decanoic acid in ethanol

Soak lead coupon for up to 24 hours in solution

Clean lead coupon with P1200 SiC paper wet with propanol or parafin.

Polish with 1m alumina paste in water

Ultrasonic in propanol

Burnish on hydroentangled polypropylene cloth.

Dry in air

Ultrasonic in propanol


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Ethanolic Pb(C10)2 Interval 76 s First 20 images


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Growth of lead decanoate from ethanolic solution

time / hours

0 1 2 3 4 5

Scaledinten

sity

0.0

0.1

0.2

0.3

0.4

Pb(C10)2 22.9o

Pb(C10)2 12o

Pb(C10

)2

15.2o

Pb

PbO


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Drying Sequence Pb(C10)2 from ethanolic solution

time / minutes

0 5 10 15 20 25 30

Scaledintensity

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Pb

PbO

Pb(C10)2 15.2o

Pb(C10)2 12o

Pb(C10)2 22.9o


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Conclusions

Time-resolved SR-XRD spectroscopy allows the growth and exposure

of passivating layers to be measured as it happens, and in parallel withother measurements.

Lead Carboxylate - Pb(C10)2 looks promising as a corrosion inhibitor for lead

- initially a 2-D areal growth (parabolic) followed by1-D vertical growth (linear)

Simultaneous electrochemical measurements allow the coating to bemonitored simply

- OCP might be developed as an end-point indicator

- EIS is a guide to coating quality

Ethanolic solutions look promising up to Pb(C18

)2


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Bibliography Rocca, E.; Steinmetz, J. Cor. Sci. 2001, 43, 891

C. Degrigny, R. Le Gall, Stud. Conserv. 1999; 44, 157.

F. Lacouture, M. Franois, C. Didierjean, J. Rivera, E. Rocca, J. Steinmetz, Acta Cryst. 2001;C57, 530

E. Rocca, C. Rapin, F. Mirambet, Cor. Sci. 2004; 46, 653.

M. Dowsett, A. Adriaens, Anal. Chem. 2006; 78, 3360

A. Adriaens, M. Dowsett, K. Leyssens, B. Van Gasse, Anal. Bioanal. Chem. 2007;387(3), 861.

De Wael, K., M. DeKeersmaecker, M. Dowsett, D. Walker, P.A. Thomas, and A. Adriaens, J.Sol. State Electrochem., 2010. 14: 407

Dowsett, M., A. Adriaens, B. Schotte, G. Jones, and L. Bouchenoire,. Surf. Interface Anal.,2009. 41(7): 565

Dowsett, M.G., A. Adriaens, G.K.C. Jones, N. Poolton, S. Fiddy, and S. Nikitenko, Anal.Chem., 2008. 80(22): 8717

Adriaens, A., F. De Bisschop, M. Dowsett, and B. Schotte, Appl. Surf. Sci., 2008. 254(22):7351

Dowsett, M., A. Adriaens, B. Schotte, G. Jones, and L. Bouchenoire. in Metal 07: eds. C.Degrigny, R. Van Langh, I. Joosten, and B. Ankersmit: Rijksmuseum, 26

Adriaens A., and M. Dowsett, The coordinated use of synchrotron spectroelectrochemistry forcorrosion studies on heritage metals, to appear in Accounts of Chemical Research 2010

Dowsett, M. Electrochemical Study Coatings Protection and Inhibition. 2010

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