Testing corrosion inhibitors for the treatment of marine iron/waterlogged wood composite artifacts

185 Pages·2008·7.06 MB·English

by  Elsa Sangouard

Filière Conservation-restauration
Orientation objets archéologiques et ethnographiques

Testing corrosion inhibitors for the

treatment of marine iron/waterlogged

wood composite artifacts in

polyethylene glycol solutions

Mémoire présenté par :
Sangouard Elsa

Pour l’obtention du diplôme
des Hautes écoles spécialisées de Suisse occidentale

29/08/08
HEAA Arc, Filière Conservation-restauration, Orientation objets archéologiques et ethnographiques
Sangouard Elsa, 29/08/2008

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HEAA Arc, Filière Conservation-restauration, Orientation objets archéologiques et ethnographiques
Sangouard Elsa, 29/08/2008

Testing corrosion inhibitors for the

treatment of marine iron/waterlogged
wood composite artifacts in
polyethylene glycol solutions

Mémoire présenté par :
Sangouard Elsa

Pour l’obtention du diplôme
des Hautes écoles spécialisées de Suisse occidentale

29/08/08
3 / 185
HEAA Arc, Filière Conservation-restauration, Orientation objets archéologiques et ethnographiques
Sangouard Elsa, 29/08/2008

Acknowledgments

Many thanks go to:
My mentor:
Christian Degrigny, Professor-Researcher at the HEAA Arc (La Chaux-de-Fonds, Switzerland) and
coordinator of the ICOM-CC Metal Working group, for his assistance and support over the year as well as
for his thorough review.

My supervisor:
Eric Nordgren, Senior Conservator at TMM® (Newport News, Virginia, USA), for his guidance, support,
patience, and significant readings.

As well as:
Marcie Renner, Chief Conservator at TMM®, for welcoming me at the Batten Conservation Complex,
providing me access to all the infrastructure and materials required for this study and for her support
throughout the year.
Dr. Desmond C. Cook, physics professor at the Old Dominion University (Norfolk, Virginia), for welcoming
me to the laboratory, providing me access to the potentiostat, as well as X-Ray Diffraction (XRD) analyses
and help with many questions.

To the following institutions:
The Old Dominion University (Norfolk, Virginia), The National Oceanic and Atmospheric Administration
(NOAA) and The Mariner’s Museum® (Newport News, Virginia) for equipment, materials, welcoming me
and for financial funding.

Special thanks for their help to:
Erin Secord, Conservator at TMM®, for her remarkable support throughout the year, for her scientific and
literary assistance.
Susanne Grieve, Conservator at TMM®, for her support, input in providing analogue materials as well as
for sharing her experience with waterlogged organic conservation.
David Krop, Conservation Project Manager at TMM®, for encouragement as well as his editing advice.
Stéphanie Hollner, PhD Student, Laboratoire de Recherche des Monuments Historiques (LRMH, Champs-
sur-Marne, France), for welcoming me at the LRMH and for sharing her knowledge about carboxylates, as
well as remaining readily available for questions throughout the year.
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Elodie Guilminot, Conservation Scientist at Arc’Antique (Nantes, France), for her advices and help over the
year, notably about Hostacor IT®.
Thanks as well to Tina Gutshall, Assistant Conservator, Gary Paden, Artifacts Handler and Michael Saul,
Technician at TMM®, for welcoming me and helping me over the year.
And also to Chief Warrant Officer 2nd Class Kasztelan and Petty Officer 1st Class Jesse Hamilton for their
help in looking for analogue material.

My school and my professors:
Valentin Boissonnas, Metal conservation professor at the HEAA Arc, for his encouragements about this
study. As well as Nathalie Ducatel, Director, HEAA Arc, Christian Binet, Tobias Schenkel, Alexis Domjan
and Julita Beck for their support during my education.

I owe thanks to the following people for their individual support throughout the year during this project:
Alain Sangouard; Mathias Sangouard; Aude-Laurence Pfister; Noemie Van de Peol; Héloïsa Munoz; Claire
Bancel; Loubna and Masson Hoggard; Ubie and Damamas Reed; Anushkush and Dreadopher Garrett;
Stefanie Bruhin; Marie Ivanco and of course Mr. Reed.
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Contents
ACKNOWLEDGMENTS......................................................................................................................4
CONTENTS..................................................................................................................................6
ABSTRACT.................................................................................................................................13
RESUME....................................................................................................................................14
ZUSAMMENFASSUNG.....................................................................................................................16
1. INTRODUCTION...............................................................................................................18
1.1. GENERAL INTRODUCTION TO THE SUBJECT...................................................................................18
1.2. CHOICE OF THE MATERIAL FOR THIS PROJECT................................................................................19
1.3. OBJECTIVES AND METHODOLOGY...............................................................................................20
1.4. THE MARINERS’ MUSEUM® (NEWPORT NEWS, VIRGINIA).................................................................21
1.4.1. The USS Monitor.........................................................................................................21
1.4.2. The Batten Conservation Complex at The Mariner’s Museum®.........................................22

Part I: Study and conservation of non-separable marine iron/wood
artifacts: an overview
2. INTRODUCTION TO THE BURIAL ENVIRONMENT: SEAWATER........................................26
2.1. SALINITY............................................................................................................................26
2.2. DISSOLVED OXYGEN...............................................................................................................27
2.3. PH, TEMPERATURE AND DEPTH..................................................................................................27
2.4. BIOLOGICAL CONSIDERATION...................................................................................................28
3. COMPOSITION, DEGRADATION AND TREATMENT OF WATERLOGGED WOOD...............29
3.1. CHEMICAL NATURE OF WOOD TISSUE..........................................................................................29
3.2. WOOD CHARACTERISTICS........................................................................................................31
3.2.1. Wood anatomy...........................................................................................................31
3.2.2. Water content.............................................................................................................32
3.3. DECAY OF WATERLOGGED WOOD...............................................................................................32
3.3.1. During burial..............................................................................................................32
3.3.1.1. Chemical decay...................................................................................................................33
3.3.1.2. Biological degradation.........................................................................................................34
3.3.2. Post excavation...........................................................................................................36
3.4. TREATMENTS OF WATERLOGGED WOOD.......................................................................................37
3.4.1. Cleaning.....................................................................................................................37
3.4.2. Consolidation..............................................................................................................39
3.4.2.1. Polyethylene glycol..............................................................................................................39
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3.4.2.2. Impregnation with resin using a non-aqueous solvent...........................................................41
3.4.2.3. Sugar impregnation.............................................................................................................41
3.4.2.4. in situ polymerization..........................................................................................................42
3.4.3. Drying........................................................................................................................42
3.4.4. Storage......................................................................................................................44
4. COMPOSITION, CORROSION AND TREATMENT OF MARINE IRON BASED ARTIFACTS..45
4.1. IRON STRUCTURE AND GENERAL PRINCIPLE OF CORROSION ...............................................................45
4.2. DEGRADATION OF SUBMERGED IRON BASED ARTIFACTS....................................................................47
4.2.1. Electrochemical reactions involved................................................................................48
4.2.2. Biological aspect.........................................................................................................49
4.2.2.1. Formation of the concretion “gangue”..................................................................................49
4.2.2.2. Further corrosion through microrganisms.............................................................................50
4.2.3. Influences of the concentration of carbon on the corrosion of iron based alloys................50
4.2.3.1. Cast iron.............................................................................................................................50
4.2.3.2. Wrought iron......................................................................................................................51
4.3. DETERIORATION AFTER EXCAVATION..........................................................................................51
4.4. CONSERVATION OF MARINE IRON BASED ARTIFACTS........................................................................52
4.4.1. Storage prior to treatment...........................................................................................52
4.4.1.1. Dissolved oxygen removal...................................................................................................52
4.4.1.2. Passivation in alkaline solution.............................................................................................53
4.4.1.3. Corrosion inhibitors.............................................................................................................54
4.4.1.4. Cathodic protection.............................................................................................................55
4.4.2. Removing concretions.................................................................................................55
4.4.2.1. Mechanical cleaning............................................................................................................56
4.4.2.2. Electrochemical cleaning......................................................................................................56
4.4.3. Stabilization................................................................................................................58
4.4.3.1. Electrolysis (cathodic polarization)........................................................................................58
4.4.3.2. Other options......................................................................................................................59
4.4.4. Final conservation steps...............................................................................................60
4.4.4.1. Rinsing...............................................................................................................................60
4.4.4.2. Drying and final cleaning.....................................................................................................61
4.4.4.3. Coating..............................................................................................................................61
4.4.4.4. Storage and display.............................................................................................................61
5. APPLICATION TO NON-SEPARABLE MARINE IRON/WOOD COMPOSITE ARTIFACTS.....63
5.1. COMPOSITES DEFINITION AND TYPOLOGY.....................................................................................63
5.2. SPECIFIC DEGRADATION OF MARINE IRON/WOOD COMPOSITE ARTIFACTS..............................................65
5.3. CURRENT TREATMENTS FOR NON-SEPARABLE MARINE IRON/WOOD COMPOSITES ARTIFACTS........................68
5.3.1. Storage of iron/wood composites before treatment........................................................68
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5.3.1.1. Reburial..............................................................................................................................68
5.3.1.2. Storage in water.................................................................................................................68
5.3.1.3. Storage in water under impressed current............................................................................69
5.3.1.4. Storage in sodium carbonate...............................................................................................70
5.3.1.5. Storage in corrosion inhibitors..............................................................................................70
5.3.1.6. Storage in ammonium citrate and PEG 400 at neutral pH......................................................70
5.3.1.7. Review...............................................................................................................................71
5.3.2. First treatment steps: documentation, concretion and salts removal................................71
5.3.2.1. Documentation...................................................................................................................71
5.3.2.2. Concretion removal.............................................................................................................72
5.3.2.3. Removal of the metallic salts from wood..............................................................................73
5.3.2.4. Removal of chlorides...........................................................................................................73
5.3.2.5. Rinsing...............................................................................................................................74
5.3.3. Impregnation and consolidation of wood component......................................................75
5.3.3.1. Iron corrosion in PEG..........................................................................................................75
5.3.3.2. An alternative to PEG: non aqueous solutions.......................................................................76
5.3.3.3. Aqueous consolidation solutions and corrosion inhibitors.......................................................79
5.3.4. Drying........................................................................................................................83
5.3.5. Post-treatment storage................................................................................................83
5.4. THE GUN CARRIAGES OF THE USS MONITOR: AN EXAMPLE OF LARGE AND COMPLEX COMPOSITES.................84
5.4.1. Description.................................................................................................................84
5.4.2. Discussion of possible treatments.................................................................................85
5.4.2.1. Removing mineral salts from the metal.................................................................................85
5.4.2.2. Wood treatment..................................................................................................................85
5.4.2.3. Drying................................................................................................................................86
5.4.2.4. Post-treatment storage........................................................................................................86
6. SYNTHESIS AND PERSPECTIVES OF CURRENT RESEARCH.............................................87

Part II: Effectiveness of corrosion inhibitors in PEG solution: experimental
protocol and analytical methods
7. MATERIALS AND METHOD...............................................................................................90
7.1. REFERENCE MATERIAL............................................................................................................90
7.1.1. Bare carbon steel........................................................................................................90
7.1.2. Analogue material: corroded carbon steel......................................................................90
7.1.3. Sample preparation.....................................................................................................91
7.2. SOLUTIONS.........................................................................................................................93
7.2.1. PEG solutions..............................................................................................................93
7.2.2. Hostacor IT®..............................................................................................................94
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7.2.3. Sodium nitrite.............................................................................................................95
7.2.4. Sodium carboxylates...................................................................................................96
7.3. EXPERIMENTAL PROCEDURE......................................................................................................98
7.3.1. Set up overview..........................................................................................................98
7.3.2. Corrosion potential monitoring versus time..................................................................100
7.3.2.1. Definition of E ...............................................................................................................100
corr
7.3.2.2. Material required...............................................................................................................101
7.3.2.3. Interpretation of E over time results...............................................................................102
corr
7.3.3. Voltammetry.............................................................................................................102
7.3.4. Accelerated aging in a humidity chamber....................................................................104

Part III: Results and study
8. ELECTROCHEMICAL ACTIVITY OF THE SOLUTIONS......................................................107
8.1. ELECTROCHEMICAL ACTIVITY OF PEG 400 SOLUTIONS..................................................................107
8.2. ELECTROCHEMICAL ACTIVITY OF THE 20% (V/V) PEG 400 / HOSTACOR IT® SOLUTION.........................109
8.3. ELECTROCHEMICAL ACTIVITY OF THE 20% (V/V) PEG 400 / NANO2 SOLUTION...................................110
8.4. ELECTROCHEMICAL ACTIVITY OF THE 20% (V/V) PEG 400 / CARBOXYLATATION SOLUTION.....................111
8.5. ELECTROCHEMICAL ACTIVITY OF THE 20% (V/V) PEG 400 / NAC10 SOLUTION....................................112
8.6. CONCLUSIONS ON ELECTROCHEMICAL BEHAVIOR OF THE SOLUTIONS..................................................113
9. CORROSION BEHAVIOR OF STEEL SAMPLES IN 20% (V/V) PEG 400...........................114
9.1. BARE METAL......................................................................................................................114
9.2. CORRODED METAL...............................................................................................................116
10. CORROSION BEHAVIOR OF STEEL SAMPLES IN 20% (V/V) PEG 400 / 1% (V/V)
HOSTACOR IT® MIXTURES......................................................................................................118
10.1. ELECTROCHEMICAL BEHAVIOR OF CARBON STEEL IN 20% (V/V) PEG 400 / 1% (V/V) HOSTACOR IT®.....118
10.1.1. Bare metal..............................................................................................................118
10.1.1.1. Behavior in 1% (v/v) Hostacor IT® in water......................................................................118
10.1.1.2. Behavior in 20% (v/v) PEG 400 / 1% (v/v) Hostacor IT®...................................................119
10.1.1.3. Behavior in 1% (v/v) Hostacor IT® first, then in 20% (v/v) PEG 400..................................120
10.1.2. Corroded metal.......................................................................................................121
10.1.2.1. Behavior in 1% (v/v) Hostacor IT® in water......................................................................121
10.1.2.2. Behavior in 20% (v/v) PEG 400 / 1% (v/v) Hostacor IT®...................................................122
10.1.2.3. Behavior in 1% (v/v) Hostacor IT® first, then in 20% (v/v) PEG 400..................................123
10.1.3. Comparison of results..............................................................................................124
10.2. ACCELERATED CORROSION TESTS...........................................................................................125
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10.2.1. Voltammetry in concentrated PEG 400 solution: long term effect of PEG on metal after
treatment...............................................................................................................................125
10.2.1.1. Bare metal......................................................................................................................125
10.2.1.2. Corroded metal...............................................................................................................127
10.2.2. Exposure to a humidity chamber...............................................................................128
11. CORROSION BEHAVIOR OF STEEL SAMPLES IN MIXTURES 20% (V/V) PEG 400 /
100PPM NANO ........................................................................................................................129
2
11.1. ELECTROCHEMICAL BEHAVIOR OF CARBON STEEL IN 20% (V/V) PEG 400/ 100PPM NANO2..................129
11.1.1. Bare metal..............................................................................................................129
11.1.1.1. Behavior in 100ppm NaNO in water.................................................................................129
2
11.1.1.2. Behavior in 20% (v/v) PEG 400 / 100ppm NaNO ..............................................................130
2
11.1.1.3. Behavior in 100ppm NaNO first, then in 20% (v/v) PEG 400.............................................131
2
11.1.2. Corroded metal.......................................................................................................132
11.1.2.1. Behavior in 100ppm NaNO in water.................................................................................132
2
11.1.2.2. Behavior in 20% (v/v) PEG 400 / 100ppm NaNO solution.................................................133
2
11.1.2.3. Behavior in 100ppm NaNO first, then in 20% (v/v) PEG 400.............................................134
2
11.1.3. Comparison of results..............................................................................................134
11.2. ACCELERATED CORROSION TESTS...........................................................................................136
11.2.1. Voltammetry in concentrated PEG solution: long term effect of PEG on metal...............136
11.2.1.1. Bare metal......................................................................................................................136
11.2.1.2. Corroded samples...........................................................................................................137
11.2.2. Exposure to a humidity chamber...............................................................................138
12. CORROSION BEHAVIOR OF STEEL SAMPLES IN MIXTURES 20% (V/V) PEG 400 /
CARBOXYLATATION SOLUTION..............................................................................................140
12.1. ELECTROCHEMICAL BEHAVIOR OF CARBON STEEL IN 20% (V/V) PEG 400/ CARBOXYLATATION SOLUTION..140
12.1.1. Bare samples..........................................................................................................140
12.1.1.1. Behavior in carboxylatation solution.................................................................................140
12.1.1.2. Behavior in 20% (v/v) PEG 400 / carboxylatation solution.................................................141
12.1.2. Corroded samples...................................................................................................142
12.1.2.1. Behavior in carboxylatation solution.................................................................................142
12.1.2.2. Behavior in 20% (v/v) PEG 400 / carboxylatation solution.................................................143
12.1.2.3. Behavior in carboxylatation solutionfirst, then in 20% (v/v) PEG 400.................................143

12.1.3. Comparison of results..............................................................................................144
12.2. ACCELERATED CORROSION TESTS...........................................................................................145
12.2.1. Voltammetry in concentrated PEG solution: long term effect of PEG on metal...............145
12.2.1.1. Bare metal......................................................................................................................145
12.2.1.2. Corroded metal...............................................................................................................146
12.2.2. Exposure to a humidity chamber...............................................................................148
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