letardi, p. y cano, e. electrochemical protection systems metal artefacts. 2010

8/7/2019 Letardi, P. y Cano, E. Electrochemical Protection Systems Metal Artefacts. 2010

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ElectrochemistryinHistoricalandArchaeologicalConservation

WorkshopJan

uary11-152010

,Leiden,TheNetherlands

Electrochemical Assessment ofProtection Systems on Metal

Artefacts

P. LetardiCNR - ISMAR, Genoa, Italy

E.CanoCENIM-CSIC, Madrid, Spain


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Introduction

Basic of EIS

Overview of commercially availableinstruments

Electrochemical cell and electrolyte

Data acquisition, representation andanalysis

Test of coatings for cultural heritage


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Basic of EIS

Energyleve

l(Potentia

lE)

Ref- - - -

Charge flow (Current I)

++ + +

The fundamental approach of

all impedance methods is to

apply a small amplitudesinusoidal excitation signal to

the system under investigation

and measure the response.

Theoretical Electrochemical

systems are usually

characterised by non-linear I-Ecurve .

A low amplitude sine wave

DEsin(wt), of a particular

frequency, is superimposed on

the dc polarization voltage E0.

This results in a currentresponse of a sine wave

DIsin(wt+f) superimposed on

the dc current I0. The current

response is shifted with

respect to the applied

potential.


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Basic of EIS

Perturbation: E(t)=E0 cos(w t) System response : I(t)=I0 cos(w t-f ) Response function: Z (w) = E/I


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Basic of EIS

Z(w) is a complex quantity with a magnitude and aphase shift which depends on the frequency of the

signal. Therefore by varying the frequency of the

applied signal one can get the impedance of the

system as a function of frequency.

Typically in electrochemistry, a frequency range of

100kHz 0.1Hz is used.

The plot of the real part of impedance on the X-axis

and the imaginary part on the Y-axis gives a

Nyquist Plot. While plotting data in the Nyquistformat the real axis must be equal to the imaginary

axis so as not to distort the shape of the curve. The

advantage of Nyquist representation is that it gives

a quick overview of the data and by the shape of

the curve one can make some qualitative

interpretations of the data. The disadvantage is that

one loses the frequency dimension of the data.

The absolute value of impedance (|Z|=Z0) and the

phase shifts are plotted on the Y-axis with log

frequency on the X-axis in two different plots giving

a Bode plot. This is the more complete way ofpresenting the data.

Zre

Zim

w0w

|Z|

Nyquist Plot|Z|

101

102

103

104

105

frequency [Hz]

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

-90

-60

-30

0

Bode Plot


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EIS spectrum can provide

information about

electrochemical processes...

and interface

properties

C.Gabrielli Identification of Electrochemical Processes by FrequencyResponse Analysis, (1998)

http://accessimpedance.iusi.bas.bg/vlab2/e-school/tech04.pdf

A.Amirudin, D.Thierry Application of electrochemical impedance

spectroscopy to study the degradation of polymer-coated metals,Prog. Org. Coat. 26 (1995) 1-28

The EIS technique(Electrochemical Impedance Spectroscopy)

Basic of EIS


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Basic of EIS

Electrochemical Impedance Spectroscopy (EIS): 1. Basic Principles

http://www.ecochemie.nl/download/content/Appl011.pdfElectrochemical Impedance Spectroscopy (EIS): 2. Experimental Setup

http://www.ecochemie.nl/download/content/Appl012.pdf

Basics of Electrochemical Impedance Spectroscopy

http://www.gamry.com/App_Notes/EIS_Primer/EIS_Primer_2007.pdf

Basics of Electrochemical Impedance Spectroscopy

http://new.ametek.com/content-manager/files/PAR/078.pdf

Electrochemical Impedance Measurements: Instruments and Techniques

http://new.ametek.com/content-manager/files/PAR/079c.pdf

http://www.solartronanalytical.com/Pages/Electrochemistry.htm
http://www.ecochemie.nl/download/content/Appl011.pdfhttp://www.ecochemie.nl/download/content/Appl012.pdfhttp://www.gamry.com/App_Notes/EIS_Primer/EIS_Primer_2007.pdfhttp://new.ametek.com/content-manager/files/PAR/078.pdfhttp://new.ametek.com/content-manager/files/PAR/079c.pdfhttp://new.ametek.com/content-manager/files/PAR/079c.pdfhttp://new.ametek.com/content-manager/files/PAR/079c.pdfhttp://new.ametek.com/content-manager/files/PAR/079c.pdfhttp://new.ametek.com/content-manager/files/PAR/078.pdfhttp://new.ametek.com/content-manager/files/PAR/078.pdfhttp://new.ametek.com/content-manager/files/PAR/078.pdfhttp://www.gamry.com/App_Notes/EIS_Primer/EIS_Primer_2007.pdfhttp://www.ecochemie.nl/download/content/Appl012.pdfhttp://www.ecochemie.nl/download/content/Appl011.pdf


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Instruments and methods

E I

CEWE

Electrolyte

Potentiostat

FRA

REF

PersonalComputer

Commercially available instruments


WE Working Electrode:

the electrode under investigation

CE Counter Electrode:

the electrode necessary to close the electrical circuit

REF Reference Electrode:

the electrode used to determine the potential of the

working electrode precisely

Electrolyte:

It ensures electrical conductivity between WE and CE

Potentiostat: it is used to fix the DC value and to

apply a sinusoidal perturbation over it

Frequency Response Analyzer (FRA): controls

the EIS scan and impedance evaluation

Acquisition Software: controls Potentiostat and

FRA, and store data file


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3 electrodeflat plate cell

WE: coated metal

RE: Usually SCE orAg/AgCl

CE: platinum,

graphite orstainless steelmesh, wire or rod


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Immersion cell

Testing of waxcoatings

C. Price et al , Proceedings of Metal 95,James&James, London (1997) 233-241


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Immersion cell

Testing of oilcoatings

D. Hallam et al, Proceedings of Metal 04, NationalMuseum of Australia, Canberra (2004) 388-399


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a contact probe setup

measurement method

has been developed to

make measurements on

art object also

CE

REF

Cloth soaked with mineral water

Contact

probe

WE


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ST Contact ProbeCE: Stainless Steel

AISI 316

REF: Stainless Steel

AISI 316

inserted in PTFE

= 1.5 cmA= 1.77 cm2

REF

CE

REF cable

CE cable

Letardi P., in: P.A.Vigato (Ed.), The Science of Art, Outdoor bronze protective coatings: characterisation by a new contact-probeElectrochemical Impedance measurements technique, Libreria Progetto di Padova, 2002, pp. 173-178

Instruments and methodsElectrochemical cell and electrolyte


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Integrated cell+EIS electronics

E. Angelini et al, IEEE Transactions on Instrumentation and Measurement 55 (2006) 436-441


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Electrolyte: as close as possible to thereal environment of the object orspecially aggressive towards demetal/coating

NaCl 0.1M

Harrison (0.35% (NH4)2SO4+0.05% NaCl)

Mineral water (Letardi)

K2SO4 0.25M (Hallam)

Acetic acid (Dowsett)

P. Letardi et al., Proceedings of Metal 98, James&James, London (2001) 303-308

D. Hallam et al, Proceedings of Metal 04, National Museum of Australia, Canberra (2004) 388-399M. Dowsett et al., Proceedings of Metal 07, Rijkmuseum Amsterdam (2007) 26-31


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Overview of commercially available instruments

http://www.ecochemie.nl/?pag=7

http://www.gamry.com/Products/Potentiostats.htm

http://www.princetonappliedresearch.com/products/potentiostats.cfm

http://www.solartronanalytical.com/Pages/Electrochemistry.htm


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Overview of commercially available instruments

Transportable instrumentation

Gamry FAS1 Femtostat

Portable instrumentation

Gamry Ref600


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Data acquisition and representation

Bode plot Nyquist plot

E. Cano, D. Lafuente, D.M. Bastidas, J. Solid State Electrochem. 14(2010) 381-391

Do not miss phase angle graph!

Same scale!


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Bode vs. Nyquist

C. Gabrieli, Use and Application of Electrochemical Impedance

Techniques TECHNICAL REPORT NUMBER 24. Solartron Analytical (1997)


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Data analysis

Physio-chemical model from first principles

Equivalent circuits (EC)

Evaluation of single parameters (|Z| at lowfrequency, C coating, etc.)


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Equivalent circuits

EC= analogues that reproduce theelectrical properties of our system

Pasive elements: resistors, capacitors,inductances, and other special elements(CPE, Warburg Impedance, etc.)

Many circuits can be used to model the

same data


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Equivalent circuits

Gamry Instruments (2007) Basics of electrochemical impedance spectroscopyhttp://www.gamry.com/App_Notes/EIS_Primer/EIS_Primer_2007.pdf

A good fitting does not mean you choosed a good model!

h b


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The basic EC

Intact coating

10-3

10-2

10-1

100

101

102

103

104

105

-90-80

-70

-60

-50-40

-30

-20-10

0

100

101

102

103

104

105

106

107

10810

910

10

(b)

PhaseAnglef

Frequency / Hz

(a)

ImpedandeModulus|Z|/cm

2

20 40 60 80 100

-20

-40

-60

-80

-100

-Z"

/Mcm

2

Z' / M cm2

h b


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The basic EC

Damaged coating

10-3

10-2

10-1

100

101

102

103

104

105

-90-80

-70

-60

-50-40

-30

-20-10

0

100

101

102

103

104

105

106

107

10810

910

10

(b)

PhaseAnglef

Frequency / Hz

(a)

ImpedandeModulus|Z|/cm

2

20 40 60 80 100

-20

-40

-60

-80

-100

-Z"/kcm

2

Z'/ k cm2

2 4

-2

-4

h b C


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The basic EC

Damaged coating(CPE)

20 40 60 80 100

-20

-40

-60

-80

-100

-Z"/kcm

2

Z'/ k cm2

2 4

-2

-4

10-3

10-2

10-1

100

101

102

103

104

105

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

100

101

102

103

104

105

106

107

108

109

1010

(b)

PhaseAnglef

Frequency / Hz

(a)

ImpedandeModulus

|Z|/cm

2

Th b i EC


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The basic EC

Damaged coating(CPE)

wjYZCPE

0

1

=1 CPE=C =0 CPE=R =-1 CPE=L =0.5 CPE=W

Usually, CPE is interpreted as an imperfect capacitor

Th b i EC


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The basic EC

Difussion(Warburg Imped.)

20 40 60 80 100

-20

-40

-60

-80

-100

-Z"/Mcm

2

Z'/ M cm2

10-3

10-2

10-1

100

101

102

103

104

105

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

100

101

102

103

104

105

106107

108

109

1010

(b)

PhaseAnglef

Frequency / Hz

(a)

ImpedandeModulus

|Z|/cm

2

O h EC


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Other EC

Multiple paralel R-C

S-J. Lee and S-I Pyun, J Solid State Electrochem 11 (2007)829-839

O h EC


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Other EC

Multiple nested R-C

M. Evesque, M. Keddam and H. Takenouti, Electrochim.Acta 49 (2004) 2937-2943

Si l EIS t


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Single EIS parameters

|Z| max or |Z| low f C coat C

DL f min high f

EIS l i ft


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EIS analysis software

Zview (Scribner) EIS300 (Gamry)

PowerSine (PAR)

EIS SpectrumAnalyser (freeware!!!)

http://www.abc.chemistry.bsu.by/vi/analyser/

T t f ti f lt l h it
http://www.abc.chemistry.bsu.by/vi/analyser/http://www.abc.chemistry.bsu.by/vi/analyser/


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UN MN UA

Natural

80 years

urban

20 m

brochantite

|Z|10mHz = 69 18 K

Natural

1 year

marine

30 m

Atacamite|Z|10mHz = 5 2 K

Artificial

Pichler

process

80 m

brochantite|Z|10mHz = 29 4 KUrban artificial UA Substrate

Treatment

none Tref T1S T2S T3S

|Z| 10mHz

[K]

100

101

102

103

104

105

UA substrate

Urban Natural UN Substrate

Treatment

none Tref T1S T2S T3S I1S Iref

|Z| 10mHz

[K]

100

101

102

103

104

105

UN substrate

UN substate (1)

Marine natural MN Substrate

Treatment

none Tref T1S T2S T3S I1S Iref

|Z| 10mHz

[K]

100

101

102

103

104

105

MN substrate

Patina plays arelevant role

on coatingbehaviour

composition thickness texture

porosity



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[C]

[B

]

[D]

[A] [F]

[E]

[A] - Soter 201LC

[B] - R21

[C] - Tromm TeCe 3534F

[D] - Incralac

[E] - Incralac+Soter

[F] - Incralac+R21

Test on monuments could be prone to several limitations: accessibility

outdoor measurements

variables out of control

authorisations



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Test on monuments could be prone to several limitations:

previous restoration treatments are also to be considered carefully

Test of coatings for c lt ral heritage


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Coupons for testing:

alloy composition dimension

patina

natural (new)

natural (old)

artificial

characterisation

Coating application:

method thickness

characterisation



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wheatering:

Multiple coupons for statistical reasons

naturalEN ISO 8565 Metals and alloys Atmospheric

corrosion testingGeneral requirements for field

tests.

artificialEN ISO 11341 - Paints and varnishes. Artificial

weathering and exposure to artificial radiation.

Exposure to filtered xenon-arc radiation

EN ISO 9227 - Corrosion tests in artificial

atmospheres. Salt spray tests



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Because of the large number of variables

involved, one need several coupons in order

to check the behaviour

Statistical methods such as Experimental

Design could be of great help in order toreduce the number of experiments required

http://www.itl.nist.gov/div898/handbook/pri/section3/pri3.htm

http://www.chemometrics.se/images/stories/pdf/aug2002.pdf

J. A. Bishopp, M. J. Parker and T. A. OReilly, The use of statistical experimental design procedures in

the development and robust manufacture of a water-based, corrosion-inhibiting adhesive primer,

International Journal of Adhesion and Adhesives 21,(2001), 473-480M.J. Anderson, P.J. Whitcomb, Design of experiments for coatings, in A.A. Tracton, Coatings

Technology Handbook, Third Edition, 3rd ed., CRC Press, 2005

Further references
http://www.itl.nist.gov/div898/handbook/pri/section3/pri3.htmhttp://www.chemometrics.se/images/stories/pdf/aug2002.pdfhttp://www.chemometrics.se/images/stories/pdf/aug2002.pdfhttp://www.itl.nist.gov/div898/handbook/pri/section3/pri3.htm


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Further references

Cano E, Bastidas DM, Argyropoulos V, Fajardo S, Siatou A, Bastidas JM, Degrigny C (2009)Electrochemical characterization of organic coatings for protection of historic steel artefacts. Journal of

Solid State Electrochemistry, 1-11.

Cano E, Lafuente D, Bastidas DM (2009) Use of EIS for the evaluation of the protective properties ofcoatings for metallic cultural heritage: a review. Journal of Solid State Electrochemistry, 1-11.

Loveday D, Peterson P, Rodgers B (2004) Evaluation of organic coatings with electrochemicalimpedance spectroscopy: Part 1: Fundamentals of electrochemical impedance spectroscopy. JCTCoatingsTech1, 46-52.

Loveday D, Peterson P, Rodgers B (2005) Evaluation of organic coatings with electrochemicalimpedance spectroscopy. JCT CoatingsTech2, 22-27.

Loveday D, Peterspm P, Rodgers B (2004) Evalution of organic coatings with electrochemicalimpedance spectroscopy part 2: Application of EIS to coatings. JCT CoatingsTech1, 88-93.

Mansfeld F (1995) Use of electrochemical impedance spectroscopy for the study of corrosion protectionby polymer coatings. Journal of Applied Electrochemistry25, 187-202.

Letardi P., Laboratory and field test on patinas and protective coating systems for outdoor bronzemonuments, in: Ashton J., Hallam D.(Eds.), Proceedings of Metal2004, National Museum of Australia,Canberra, 2004, pp. 379-387

Joseph E., Letardi P., Mazzeo R., Prati S., Vandini M., Innovative treatments for the protection ofoutdoor bronze monuments, in: C.Degrigny, R. van Langh, I. Joosten, B.Ankersmit (Eds.), Proceedingsof Metal07, Amsterdam 2007, v5 pp. 71-77

letardi, p. y cano, e. electrochemical protection systems metal artefacts. 2010

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