Cano, E. Electrochemical Protection System Mtal Artefacts. 2010

8/7/2019 Cano, E. Electrochemical Protection System Mtal Artefacts. 2010

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Electrochemicalassessment of protection

systems for metalartefacts

Dr. Emilio Cano DazCentro Nacional de Investigaciones Metalrgicas

(CENIM)Consejo Superior de Investigaciones Cientficas

(CSIC)


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Electrochemistry in Historical and Archaeological Conservation Lorentz Center. Leiden. 11-15 January 2010

Outline

New protection systems for heritage? Pros and cons of electrochemical techniques Rp: fundamentals and applications EIS: fundamentals and applications Evaluation of innovative coatings in the

PROMET project.

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Need of new protection systems

Improved efficiency Lower toxicity Specific needs for cultural heritage

conservation: Reversibility/re-tratability Respect to original object and surface

Transparency, good visual aspect Reproducibility issues

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Testing new protection systems

Tests in laboratory coupons Difficult (impossible?) to reproduce composition

and corrosion layers

Tests in real objects: Not uniform in composition, microstructure and

patina/corrosion products Unique value of each object

Combination of both, specific protocols andnon-destructive and highly sensitivetechniques

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Testing new protection systems

Natural exposure Very reliable, but very slow

Accelerated tests in climatic chambers Fast, but too accelerated Well established for industrial applications (for

instance, salt fog test) Better for comparison purposes Not applicable to real objects

Electrochemical tests

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Advantages Very high sensibility

Measure instantaneous corrosion rate and are notdestructive: evolution of protection/corrosion withtime

Measure in real conditions: even on real objects! Relatively simple and inexpensive equipment

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1 nA/cm 2Fe Fe 2+1 hour

1,04 10 -8 g


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Disadvantages Usually need a bulk electrolyte: not real

atmospheric conditions

Interpretation might be not easy in some cases(EIS)

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Polarization resistance (Rp)

At Ecorr , the slope of the V/I curve isproportional to the corrosion rate

Stern and Geary (1957):

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Polarization resistance (Rp)

Potential sweep from +- 10 mV vs. Ecorr Usually not employed for coatings due to the

very high resistance of the coating Fast and easy to intrepret

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Electrochemical Impedance

Spectroscopy (EIS) Based on the application of a AC low

amplitude (typically 10 mV) potential signal

Frequency swept from 100 kHz to 1 mHz

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Perturbation: E(t)=E 0 cos( t)

System response : I(t)=I 0 cos( t- )

Response function: Z ( ) = E/I


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Electrochemical Impedance

Spectroscopy (EIS)

The most important technique for evaluationof corrosion protection coatings in the last 30years

Allows for the measurement of the propertiesof high resistance coatings

Can obtain information of differentprocesses/parts of your system: electrolyte,coating, corrosion processes, etc.

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History of use of EIS for CH

Pioneer work: Price, Hallam et al., Metal 95 In situ evaluation of CH objects (Letardi, Metal

98) Very important increase of the use of EIS in

CH in the last years

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Electrochemistry in Historical and Archaeological Conservation Lorentz Center. Leiden. 11-15 January 2010 13

PROMET project

PROMET:Innovative conservation approaches for monitoringand protecting ancient and historic metals collectionsfrom the Mediterranean basin 6 Framework Program E.U. INCO-MED November 2004 - April 2008 21 partners from 11 mediterranean countries

Spain: CENIM-CSIC & UAM


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Protocol to study new protectionsystems

Artificiallycorrodedcoupons

Newproductsselection

Study of realobjects

Naturallycorrodedcoupons

Real exposure

Final list ofproducts Application in real

heritage objects

Laboratorytests

Laboratorytests


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Experimental

Material: low carbon steel (0,14%) Coatings

New: Poligen ES91009 (BASF) Ready to use liquid poliethylene wax emulsion Dries in24 h. Non toxic and environmentally safe

Traditional: Paraloid B-72 and Renaissance With and without corrosion inhibitor additives Electrochemical tests (Rp and EIS)


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Coatings tested

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Experimental setup

Polarization resistance (R p) -10 +10 mV vs. OCP 0,16 mV/s

Electrochemical Impedance(EIS) 64 kHz 1mHz, 10 mV, 0 V vs. OCP

PAR 273A

Solartron 1250


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Experimental setup

Referenceelectrode

Platinummesh

(counterelectrode)

4.15 cm 2working

electrode


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Rp tests

Clean samplesID Coating

0 No coating (Blank)

1 Renaissance wax

2 Poligen ES 91009

2a Poligen ES 91009 + M435 inhibi tor

2b Poligen ES 91009 + M370 inhibi tor

3 Paralloid B-72 (15% Acetonae

3a Parallo id B-72 + M435 inhibi tor

3b Parallo id B-72 + M109 inhibi tor

3c Parallo id B-72 + Alkaterge-T

1

1

1

istance, cm

2

-2

0

2

46

8

10

12

14

16

1 2 2a 2b 3 3a 3b 3c

Sample

Thickness, micrometers


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Rp tests

Pre-corroded andaged samples

0

20

40

60

80

100

120

140

NC TC1 TC2 C1 C2 C3 C4 C5

Coating

Thickness, m

ReferenceAccelerated aged

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+051.0E+06

1.0E+07

1.0E+08

NC TC1 TC2 C1 C2 C3 C4 C5

Coating

Rp, cm

ReferenceAccelerated aged

* *

2

ID CoatingNC No coating (Blank)

TC1 15% Paraloid B-72 in acetone

TC2 Renaissance wax

C1 Poligen ES 91009

C2 Poligen ES 91009 + M370

C3 Poligen ES 91009 +M435

C4 15% Paraloid B-72 in acetone + Alkaterge-T

C5 15% Paraloid B-72 in acetone + M109


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R S

R 1

C dl

EIS results

10-1 100 101 102 103 10410010110210310410510610

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Frequency (Hz)

|Z|

No coatingCoating 1Coating 2Coating 2aCoating 2b

10-1 100 101 102 103 104

-90

-45

0

Frequency (Hz)

theta

Sin recubrimiento


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EIS results

10-1 100 101 102 103 10410010110210310410510610

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Frequency (Hz)

|Z|


10-1 100 101 102 103 104

-90

-45

0

Frequency (Hz)

theta

Y 0F /cm 2 s

(1- )

2.8 10-3

0.74 2681

CPE 1

R 1 cm 2

jY Z CPE

0

1

CPE 1R S

R 1

Sin recubrimiento


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EIS results

10-1 100 101 102 103 10410010110210310410510610

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Frequency (Hz)

|Z|


10-1 100 101 102 103 104

-90

-45

0

Frequency (Hz)

theta

Rennaissance wax

Y 0 Y 0F /cm 2 s

(1- ) F /cm 2 s(1- )

0.4 10 -3 0.8 22.86 0 .3 10 -3 0.79 2960

R 2 cm 2

CPE 1 CPE 2 R 1

cm 2

CPE 1

CPE 2

R S

R 1

R 2


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EIS results

10-1 100 101 102 103 10410010110210310410510610

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Frequency (Hz)

|Z|


10-1 100 101 102 103 104

-90

-45

0

Frequency (Hz)

theta

Poligen ES 91009

Y 0 Y 0

F /cm 2 s(1- ) F /cm 2 s

(1- )

0.4 10 -3 0.76 2162 59 10 -3 0.51

1.17 10 -6 0.76 82442 2.7 10 -5 0.58

8.89 10 -9 0.96 280810 8.3 10 -7 0.47

CPE 1 CPE 2 R 1

cm 2

CPE 1

CPE 2

R S

R 1


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10-1 100 101 102 103 104100

101102103104105106107

Frequency (Hz)

|Z|

No coatingCoating 3Coating 3aCoating 3bCoating 3c

10-1 100 101 102 103 104

-90

-45

0

Frequency (Hz)

theta

EIS resultsParaloid B72

Y 0 Y 0

F /cm 2 s(1- ) F /cm 2 s

(1- )

2.95 10 -7 0.56 16725 4.6 10 -6 0.5 34825

0.39 10-3

0.5 407 1.2 10-3

0.82 1395

4.53 10 -7 0.65 32228 1.0 10 -6 0.63 1.29 10 6

2.14 10-7

0.65 8031 7 .6 10-6

0.54 28949

R 2 cm 2

CPE 1 CPE 2 R 1

cm 2

CPE 1

CPE 2

R S

R 1

R 2


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Conclusions

Electrochemical tests give a quantitativeinformation of the protection provided bydifferent coatings in a short time Rp provide quick and easy to interpret results EIS provide in-depth information on the corrosion

and protection mechanisms


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Conclusions

The addition of corrosion inhibitor additivesdid not provide and improvement of theprotection, and in some cases have a

negative effect. Poligen ES91009 provides better protection

than Paraloid B72 when applied in thick layers

Rennaissance provides very little protection

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PROMET: additional information

CSSIM conference proceedings Strategies forsaving our cultural heritage

Book Metals and Museums in the Mediterranean.

Protecting, preserving and interpreting

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Further reading 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 of coatings formetallic cultural heritage: a review. Journal of Solid State Electrochemistry, 1-11.

Ellingson LA, Shedlosky TJ, Bierwagen GP, de la Rie ER, Brostoff LB (2004) The use of electrochemical impedancespectroscopy in the evaluation of coatings for outdoor bronze. Studies in Conservation 49, 53-62.

Letardi P, Beccaria A, Marabelli M, D'Ercoli G (1998) Application of electrochemical impedance mesurements as a toolfor the characterization of the conservation and protection state of bronze works of art. In 'Metal 98. InternationalConference on Metal Conservation '. Draguignan-Figanires (France). (Eds J Ashton and D Hallam) pp. 303-308.(James & James)

Loveday D, Peterspm P, Rodgers B (2004) Evalution of organic coatings with electrochemical impedance spectroscopypart 2: Application of EIS to coatings. JCT CoatingsTech 1, 88-93.

Mansfeld F (1995) Use of electrochemical impedance spectroscopy for the study of corrosion protection by polymercoatings. Journal of Applied Electrochemistry 25, 187-202.

Mansfeld F (2008) Fundamental aspects of the polarization resistance technique-the early days. Journal of Solid State Electrochemistry, 1-6. Murray JN (1997) Electrochemical test methods for evaluating organic coatings on metals: An update. Part III: Multiple

test parameter measurements. Progress in Organic Coatings 31, 375-391. Price C, Hallam D, Heath G, Creagh D, Ashton J (1995) An electrochemical study of waxes for bronze sculpture. In

'Metal 95. International Conference on Metal Conservation '. Semur-en-Auxois (France). (Eds ID MacLeod, SL Pennecand L Robbiola) pp. 233-241. (James & James)

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Electrochemistry in Historical and Archaeological Conservation

Acknowledments

Organizers of the workshop PROMET project E.U. Colleagues in the PROMET Prof. Jos Mara Bastidas

Documents

Cano, E. Electrochemical Protection System Mtal Artefacts. 2010