EAS 2005 Presentation

1
Corrosion of the Wrought Iron Turret of the USS
Monitor
Desmond Cook Physics Department and Consorti
um for Maritime Studies Old Dominion
University Norfolk, Virginia, USA
This presentation is available at www.RustDr.com
Supported by funds from National Oceanographic
and Atmospheric Administration, The Mariners
Museum. Old Dominion University
2

• USS Monitor history
• January 1862 USS Monitor constructed and
  launched
• 9 March 1862 Infamous battle of the Ironclads
  USS Monitor and CSS Virginia
• 31 December 1862 USS Monitor sank during a storm
  off Cape Hatteras.

3

• USS Monitor history
• 1973 USS Monitor discovered upside down at a
  depth of 240.
• Turret was dislodged with the hull resting on
  top.

• USS Monitor history
• Turret was full of ocean sediments.
• 1983 Anchor recovered
• 1998 Propeller and shaft recovered
• 2001Engine Condensor recovered
• 2002 Turret recovered

4

• USS Monitor history
• August 2002 USS Monitor turret raised and moved
  to the Mariners Museum, Newport News, Virginia.
• Turret contained remains of 3 crew, personal
  items, ships instruments, galley utensils, coal,
  and the two 11 Dahlgren cannons.

5
Turret Construction Diameter 20 ft. Height 9
ft. Weight 200 tons Construction Wrought Iron
8 layers, each 1 thick, Bolted
6
Part 1 Corrosion of the USS Monitor

• Goals
• General Corrosion Evaluation
• Turret
• Cannons
• Engine and Condenser
• As a result of
• Submerged Saltwater exposure for 150 years
• Recovery and Exposure to Air.
• Use Spectroscopic Analysis
• Rust identification, Source and Corrosion Rate
• Correlate rust formation with the exposure
  conditions.

7
Corrosion Evaluation

• Spectroscopic Identification
• of
• rust composition
• Iron Oxide Identification
• Oxide Mapping
• Impurity (pollutant) content (Cl, S)

• Analytical Techniques
• X-Ray Diffraction
• Mössbauer Spectroscopy
• --Transmission and Scattering
• Micro-Raman Spectrometry
• Electron Micro-Probe
• Ion Chromotography
• XAFS
• IR/UV Spectroscopy
• Ion Transport
• Electrochemical Impedance Spectroscopy

8
Turret Wall Thickness Corrosion Rate
Thickness measurements Outer and Inner sheets
¾ Thickness loss ¼ (250 mils) in 140
years 1 ½ - 2 mils per year (mpy) 50
microns/yr. (Compared with bridge corrosion 2
mpy very adverse chlorine environment 2 mpy
5-10X expected corrosion of steel). Conclusion
Corrosion rate of the turret has been high.
9
Turret rust High Time-of-Wetness, Low oxygen,
Chlorine
10
Turret Corrosion Outside
Bolt Heads
11
Turret Corrosion Inside
Submerged Corrosion Environment (Anaerobic and
salt-water)
12
Cannon Rust
13
USS Monitor Turret Rust (Unstable black
rust) Mössbauer Analysis
Magnetite and Green Rust ? Magnetite Fe3O4 ?
Maghemite ?-Fe2O3
A new corrosion product Corrosion Magnetite

Corrosion Magnetite is unstable
As the magnetite ages, the B1 site oxidizes to
the A1 site.
14
Exterior Turret Rust Magnetite, Lepidocrocite,
Goethite, Akaganeite FeSiO4 and CaCO3
Corrosion mainly due to high TOW (submersion) But
exposure to air produces Akaganeite with bound
chlorine
15
Ocean sediments
Exterior Turret Wall
16
Turret Mud FeCO3, CaCO3, Quartz
Lepidocrocite, Goethite 3 Sulfur
.MIC??? Variable pH 2-3 - 6-7
17
Rusticles On Engine and Condenser in NaOH
Composition Outer CaseCaCO3 Inside Mainly
Corrosion Magnetite This is in variation with
Rusticle analysis on the Titanic.
18
Marine growth
19
Turret Marine Growth Rust FeCO3, CaCO3, Quartz
Magnetite, Goethite, Lepidocrocite
20
Research Conclusions for corrosion

• During seawater submersion of Wrought and Cast
  Iron
• Corrosion Magnetite forms
• Unstable and oxidizes to Maghemite
• Corrosion rate very high
• Sediments exhibit low pH 2-3, high sulfur
• Possible Microbial Induced Corrosion.
• Exposure to air
• Akaganeite (with bound chlorine) forms.

21
Part 2 Metallurgical study of wrought Iron found
in the turret

• Goals
• Part 1 Metallurgical Characterization.
• Investigate the Inclusions and identify their
  composition
• Study the corrosion of the wrought iron
• Study the chlorine diffusion into the wrought
  iron
• Study the effects of exposure of the inclusions
  to air and drying
• Map the chlorine and other elements in the
  wrought iron.
• Part 2 Remove the chlorides Sub-Critical Fluid
  Extraction.
• Part 3 Confirm the chlorides have been
  completely removed.

22

• Analysis of Wrought Iron
• Polished Metallographic cross-sections
• Electron Probe Micro-Analysis (EPMA) with WDS
  (elemental analysis)
• SEM with WDS/EDS
• Micro-Raman Spectrometry. Compound identification
  (1 um spatial resolution).
• Rust identification, XRD and Mössbauer
  spectroscopy.
• ICP, IC, and Wet Chemistry for Chlorine (and
  Sulfur) analysis

23
USS Monitor Wrought Iron Sample
MNMS.2002.WI001 Recovered From the Turret Sample
Preparation 1 (Pre-Treatment Analysis)

• Metallurgy
• Pre-Treatment
• Piece1 (Long.)
• Piece 2 (Trans.)
• S/C Fluid Treatment
• Piece 5
• 3. Post-Treatment
• Piece 5A

Direction of Rolling
24
Sample Preparation 2 (S/C Treatment Cutting)
25
Sample Preparation 2 (S/C Treatment Piece 5)
26
Sample Preparation 3 (Piece 5 Post-Treatment
Cutting)
Post-Treatment Fresh Cut Surface (Mount and
Polish)
27
Pre-Treatment Analysis Piece 1. Longitudinal to
rolling direction
50X
Direction of Rolling
28
Internal Inclusions
50X
200X
500X
29
Corroded Inclusions
30
Region 4 Internal Inclusion
31
Region 4 Internal Inclusion
Electron Probe Micro Analysis with WDS
A
B
Each compound identified by Micro-Raman Analysis
32
Region 4 Internal Inclusion
Cl
Electron-Probe Micro-Analysis X-Ray Mapping Probe
Current 9 nA
Si
P
33
Region 1 Surface Inclusion (Corroded Section)
34
Region 1A Surface Inclusion (Corroded Section)
Magnetite, Fe3O4
Corrosion
Element K-ratio Z A F ZAF
Atom Wt Fe-K 0.737 1.040 1.000 1.000
1.040 51.84 76.66 Cl-K 0.014 0.984
1.272 0.993 1.243 1.89 1.78 S -K
0.008 0.943 1.392 0.995 1.305 1.30
1.10 P -K 0.018 0.968 1.565 0.997 1.510
3.25 2.66 Si-K 0.002 0.936 1.866
0.998 1.744 0.39 0.29 O -K 0.097
0.902 2.011 0.997 1.807 41.32 17.50 Total
100.00
Fayalite, Fe2SiO4 Iron Phosphate
Element K-ratio Z A F ZAF
Atom Wt Fe-K 0.825 1.029 0.998 1.000
1.027 62.09 84.75 Mn-K 0.006 1.050
1.002 1.000 1.052 0.44 0.59 O -K
0.090 0.894 1.827 0.996 1.627 37.47
14.65 Total 100.00
Each compound identified by Micro-Raman Analysis
35
Electron-Probe Micro-Analysis X-Ray Mapping Probe
Current 9 nA
Region 1A Surface Inclusion (Corroded Section)
Si
P
Cl
36
Region 1B Surface inclusion Un-corroded Section
EPMA Current 9 nA
Fayalite, Fe2SiO4 Iron Phosphate
Si
P
Cl
37
Sub-Critical Fluid Treatment Piece 5

• Sub-Critical Fluid
• Extraction of Chlorine
• Collaboration between
• Clemson University
• Warren-Lasch Laboratory
• Old Dominion University
• Mariners Museum

• Sub-Critical Treatment
• NaOH
• Time 3 Days
• Cl lt 1ppm

38
Sub-Critical Treatment Monitor Sample
5. Chlorine Concentration in Fluid
39
Post-Treatment of Sample 5
40
Post-Treatment of Sample 5 Region 1 Surface
Inclusion, Corroded Section. EPMS Analysis WDS
Surface Inclusion Corrosion Products
        Element K-ratio Z A F
ZAF Atom Wt Fe-K 0.810 1.032 0.998
1.000 1.030 59.75 83.41 Cl-K 0.000
0.978 1.264 0.992 1.227 0.00 0.00 S -K
0.000 0.937 1.395 0.996 1.301 0.00
0.00 Si-K 0.002 0.931 1.926 0.999
1.791 0.53 0.38 Na-K 0.001 0.956
5.095 1.000 4.870 1.13 0.65 P -K
0.002 0.962 1.607 0.998 1.542 0.36
0.28 O -K 0.093 0.896 1.840 0.996 1.642
38.23 15.29 Total 100.00
41
Post-Treatment of Sample 5 Region 1 EPMS
Analysis X-Ray Mapping Current 90 nA
Cl
Na
Si
P
42
Post-Treatment of Sample 5 Region 2 Surface
Inclusion Corroded Section. EPMS Analysis X-Ray
Mapping Current 90 nA
Na
Cl
Si
P
43
Post-Treatment of Sample 5 Region 6 Corrosion-
Metal interface EPMS Analysis
Cl
44

• Conclusions
• Pre-Treatment
• Surface inclusions responsible for chlorine
  diffusion
• 1-2 Cl in the inclusions
• Cl diffusion between inclusion and iron.
• Cl Depths 1-5 mm
• Silicates and Phosphates unaffected by the
  corrosion
• Inclusion widths 5 um before corrosion
• Inclusion widths 25-50 um with corrosion
• Post-Treatment
• Inclusion Material not removed (Silicates and
  Phosphates)
• Corrosion Products Removed from inclusions
• Chlorine and sulfur removed from inclusions

45
Monitor Center To open March 9,
2007 www.monitorcenter.org
46
9 September 2004