adriaens, m y dowsett, m. study chloride corrosion. 2010

8/7/2019 Adriaens, M y Dowsett, M. Study Chloride Corrosion. 2010

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An in-situ spectroelectrochemistry study of

the response of artificial chloride corrosion

layers on copper to remedial treatment

Mieke Adriaens1, Mark Dowsett2

1

Ghent University, Belgium2 University of Warwick, UK



Christian Degrigny

Mieke AdriaensMark Dowsett



archaeological copper artefacts recovered from wet saline

environments corrode at accelerated rate in oxygen-rich air

storage in a solution

tap water sodiumsesquicarbonate

solution

Photo © Western Austrialia’s Maritime Museum



Photo © Western Austrialia’s Maritime Museum

artefacts often show a certain instability

(e.g. chemical transformation of the natural patina

and development of active corrosion)

monitoring the treatment remains necessary



Present monitoring method

determination of the chlorideconcentration in solution using volumetric

analyses

– change of solution when

predetermined value is

exceeded– repetition until value low enough

disadvantages

– time consuming

– indirect monitoring method

– no idea of potential side reactions



Objective

investigate the use of corrosion potential measurements(Ecorr) to monitor the behaviour of copper based alloys

during their storage and stabilization

benefits

– simple tool

– inexpensive to conservators

– direct monitoring method of the metal surface

– more complete reaction profile when combined with the

analysis of the solution



Corrosion potential

potential difference between metal object and reference electrode

depends on

– metal composition

– solution

– interface metal – solution

hypothesis: surface composition is stable when the corrosion

potential measurements do not change as a function of time

referenceelectrode

Photo © EVTEK

object(porthole)



Strategy

Corrosion simulation Evaluate corrosion products

Immerse sample into sodium sesquicarbonate solution

Perform corrosion potential measurements as a function

of time and monitor the surface of the electrode

simultaneously



Corrosion simulation

Electrodes– reference materials with known composition

• copper

• copper-tin alloy

• copper-tin-lead alloy

Corrosion products

cuprite nantokite atacamite atacamite and

paratacamite

metal surface

(12 mm diameter)

epoxy resin

electrical connection



eCell

webcam

incoming X-rays

detector

SRS 6.2



Nantokite (CuCl) protocol*

Immersing pure coppersamples for one hour in a

saturated CuCl2.2H2O

solution

Rinsing with deionised water

Exposure to atmosphere

over night

1 mm

C. Lamy (1997) Stabilisation d’Objects Archéologiques Chlorurés en Alliage Cuivreux – Définition des Conditions d’une PolarisationCathodique à Potentiel Constant en Solution de Sesquicarbonate de Sodium 1%, Rapport du Stage, Université de Nantes ISITEM.



Nantokite

Cuprite

Cuprite

C

opper

XRD data – nantokite coated copper in 1% sodium sesquicarbonate

K. Leyssens et al., Electrochemistry Communications 7 (2005) 1265.



Elapsed time / minutes

0 50 100 150 200

Relativepeakar

ea/percent

0

20

40

60

80

100

Nantokite (29.6o)

Cuprite (37.7o)

Cuprite (43.8o)

Copper

Nantokite (49.3o)

Cuprite (43.8o) corrected for Cu

Elapsed time / minutes

0 50 100 150 200

Relativepeakar

ea/percent

0

20

40

60

80

100

Ecorr/V

-0.22

-0.20

-0.18

-0.16

-0.14

-0.12

-0.10

-0.08

-0.06

-0.04

Nantokite (29.6o)

Cuprite (37.7o)

Copper

Nantokite (49.3o)

Cuprite (43.8o) corrected for Cu

Corrosion Potential (Ecorr)

XRD dataEcorr data

K. Leyssens et al., Electrochemistry Communications 7 (2005) 1265.



XRD conclusions

Corrosion potential measurements need to be treated withcaution

Further investigations needed

• E.g. which reactions take place?

– CuCl -> Cu2O

– CuCl -> Cu -> Cu2O



Can XAS data provide additional information?

An independent means of surface characterization whichis sensitive to the presence and evolution of amorphous

compounds



XAS data from powder samples (references)

Energy / keV

8.96 8.98 9.00 9.02 9.04 9.06 9.08 9.10

normalized (E)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

8.97 8.98 8.99 9.00

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Atacamite

Copper

Cuprite

CuCl



XAS data from corroded copper samples

Energy / keV

8.96 8.98 9.00 9.02 9.04 9.06 9.08 9.10

normalized

0.0

0.2

0.4

0.6

0.8

1.0

1.2

8.97 8.98 8.99 9.00

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Atacamite

Cuprite

Nantokite

Copper



XAS data from corroded copper samples in solution

Energy / keV

8.96 8.98 9.00 9.02 9.04 9.06 9.08 9.10

normalized (

E)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

8.97 8.98 8.99 9.00

0.0

0.2

0.4

0.6

0.8

1.0

1.2Copper

Atacamite

Nantokite

Cuprite



“atacamite” (Cu2(OH)3Cl isomers ) protocol*

prepare a solution of 15.07g (NH4)2CO3.NH3 and 10.02 g

NH4Cl in 100 mL deionised

water

wet coupons twice a day

with this solution repeat procudere for 5 days

between each application,

the samples were left to dry

to the air

C. Lamy (1997) Stabilisation d’Objects Archéologiques Chlorurés en Alliage Cuivreux – Définition des Conditions d’une PolarisationCathodique à Potentiel Constant en Solution de Sesquicarbonate de Sodium 1%, Rapport du Stage, Université de Nantes ISITEM.



Time dependence – “atacamite” on copper in 1% sodium sesquicarbonate

8.9 9.0 9.1 9.2 9.3 9.4 9.5 9.6

0

10

20

30

4012

11

10

9

8

1

(E) normalized to the first scan

Energy (keV)



8.90 8.95 9.00 9.05 9.10

Energy (keV)

CuCO3

atacamite

CuCl2.2H20

Bour sample

* Add 50 mL 0.1 M Na2CO3 solution dropwise to a stirred solution of 100 mL 0.1 M CuCl2.2H2O. Boil at reflux. After 5 h filter the slurry,

wash and dry at 333 K. Crush the samples to a very fine powder.

C. Lamy (1997) Rapport du Stage, Université de Nantes ISITEM.

*



“atacamite” coated copper in 1% w/w sodiumsesquicarbonate

Time dependence



Two theta

20 40 60 80

Intens

ity

0

2000

4000

6000

8000

10000

12000

“atacamite” as obtained from protocol



Two theta

20 40 60 80

Intens

ity

0

2000

4000

6000

8000

10000

12000


after rinsing



Two theta

20 40 60 80

Intensity

0

2000

4000

6000

8000

10000

12000


after rinsing

XRD reference of atacamite



Time dependence – “atacamite” on copper in 1% sodium sesquicarbonate

8.9 9.0 9.1 9.2 9.3 9.4 9.5 9.6

0

10

20

30

40 12

11

10

9

8

1

(E)

normalized to the first scan

Energy (keV)



time/hours

0 10 20 30 40

Corrosionpote

ntial/V

(vsAg/AgClref)

-0.08

-0.06

-0.04

-0.02

0.00

Simulaneous Ecorr measurement

Fluid

change

Fluid

change



Overall reaction

Cuprite forms at the chloride/copper interface

The insoluble chlorides fall off or remain physically but not

chemically attached

The corrosion potential becomes

characteristic of a passive cuprite

covered surface but chlorides may

remain to cause further problems

Corrosion potential measurements

need to be treated with caution!



Summary simulated chloride species

Nantokite– Converts to cuprite

“Atacamite”

– Surface converts to cuprite

– “Atacamite” becomes detached

Paratacamite/atacamite

– Protocol also produces nantokite

– Nantokite converts to cuprite and can coat the hydroxychlorides



Future

Address the suitability of simulated alloys/corrosionproducts

More complex systems

– Bronzes

– Multi-layers

Long term experiments in portable cells

Photo: Paola Letardi



Acknowledgments

Karen Leyssens, Bart Schotte and Gareth Jones Pieter Van Hoe, Derrick Richards, Adrian Lovejoy

Dr. Manolis Pantos, Dr. Tony Bell, Dr. Chris Martin, SRS

Dr. Laurence Bouchenoire, Dr. Sergey Nikitenko, ESRF

Dr. Christian Degrigny, SARL Germolles

COST Action G8 - http://srs.dl.ac.uk/arch/cost-g8/



Further reading

K. Leyssens, A. Adriaens, M. Dowsett, B. Schotte, I. Oloff, E. Pantos, A. Bell andS. Thompson, Simultaneous In-situ time Resolved SR-XRD and Corrosion

Potential Analyses to Monitor the Corrosion on Copper, Electrochemistry

Communications 7 (2005) 1265-1270.

K. Leyssens, A. Adriaens, C. Degrigny, E. Pantos, Study of Corrosion Potential

Measurements as a Means to Monitor the Storage and Stabilization Processes

of archaeological Copper Artefacts, Analytical Chemistry 78(8) (2006) 2794-

280.

M. Dowsett, A. Adriaens, Cell for Simultaneous Synchrotron Radiation X-ray and

Electrochemical Corrosion Measurements on Cultural Heritage Metals and Other

Materials, Analytical Chemistry 78(10) (2006) 3360-3365.

A. Adriaens, M. Dowsett, K. Leyssens, B. Van Gasse, Insights into electrolytic

stabilization with weak polarization as treatment for archaeological copper

objects, Analytical Bioanalytical Chemistry 387(3) (2007) 861-868.

A. Adriaens, M. Dowsett, G.K.C. Jones, K. Leyssens, S. Nikitenko, An in-situ X-ray

absorption spectroelectrochemistry study of the response of artificial chloride

corrosion layers on copper to remedial treatment, J. Anal. At. Spectrom. 24(1)

(2009) 62-68.

adriaens, m y dowsett, m. study chloride corrosion. 2010

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