During a Post Installation Mooring Inspection at Mississippi Canyon block 736, curious growths were noted on the chain which are evidence of Microbiologically Influenced Corrosion (MIC). These growths were also observed on subsea shipwrecks such as the Titanic and in some conditions corrode steel at a surprising rate. Though observation of these tubercles does not accelerate their growth rate, designers should consider corrosion rates in their design even at depths of 6000 feet below sea level. Corrosion can and does occur in an anoxic environment and designers should not relax their corrosion allowances for chains at depth.
25. Steel Corrosion Model –– Melchers
Melchers
Corrosion ra rs
Loss
Localized anaerobic
cs
conditions have
developed
ca
ro ta Exposure Period
Phase 4
Phase 3
Phase 2
Phase 1
Phase 0
26. Water Temperature Impact –– Melchers
Melchers
0.4
0.35 20°C
Corrosion Loss (mm)
28°C
0.3 10°C
4°C
0.25
0.2
0.15
0.1
0.05
0
0 1 2 3 4 5 6
Exposure Period (years)
34. What Do Rusticles Do? –– Ray et. al.
Ray et. al.
Before
After
(Pitting)
35. Conclusions
• Does corrosion occur at 1800m depth?
• Is corrosion life predictable?
• Should corrosion allowances be maintained?
• Corrosion occurs in a hypoxic environment?
• ro f (T , O2 , vo , pH )
• Rusticles evidence of steel corrosion?
• Synthetic Rope Moorings corrosion solution?
36. Acknowledgements
• Co-Authors
– Luc Chabot
– Jim Jenkins
– Brett Warren
• Conference Reviewers and Administrators
– Ron Riggs
– René Huijsmans
– Joel Witz
– Johann Wichers
• American Society of Mechanical Engineers
• Kivi Niria
• OMAE 2011