Principles of Marine Corrosion References 123
Part A | 6
The marine environment is, nevertheless, severe for
concrete structures. Under suitable conditions, the chlorides in seawater can combine with the ferrous ions
released by the steel reinforcement in the corrosion
process to produce highly soluble ferrous chlorides
(FeCl 2 ), and with the sufficient availability of oxygen, very soluble ferric chloride ions (FeCl 3 ). These
can leach out of concretes very readily and leave
merely brown watery-looking rust stains rather than the
usual build-up of solid rust products responsible for
cracking, such as shown in Fig. 6.11. The corrosion
associated with FeCl 2 production can be very severe.
Figure 6.12 shows a case where apparently sound concrete, some 65 years old, without any visible external
rust staining or cracking was broken open as part of
a routine scientific investigation. It revealed almost
complete loss of about 300 mm length of reinforcement bars inside the concrete. Only some magnetite
(the black material) was left to show the location of
the bar. Figure 6.13 shows the severely corroded end
of the bar, that some small distance away, was left intact within the adjacent concrete [6.52]. Several other,
similar cases have are now available, some in summary form [6.55, 56] and detailed investigations are
proceeding. Finally, the marine environment can also
be a problem for the concrete itself [6.16, 17], but
modern practices largely have eliminated this as an
issue.
These observations show that reinforced concrete
can be a very successful construction material in marine
environments, provided a high level of alkali material
is embodied in the concrete mass, giving long-term
buffering against alkali loss through leaching. However,
it is possible for severe localized corrosion loss of reinforcement to occur without obvious external warning
signs. This latter aspect is currently under urgent investigation as the implications for existing reinforced
concrete infrastructure as significant.
6.8 Conclusion
Seawater is a complex mix of many different chemicals
and microorganisms, even though it is remarkably uniform for most parts of the world. It is usually considered
to be a hostile environment for materials and this is evident in the research efforts devoted to understanding the
initiation of corrosion and its propagation once it starts.
The present chapter has outlined some of the current
research in this area, focusing mainly on engineering
rather than purely scientific investigations. The research
is driven largely by the needs of industry but anchored
in fundamental science and the basic understanding of
the processes involved. It is focused on developing tools
and techniques that can be applied in the offshore, shipping, and coastal environment engineering industries.
The present chapter gives an overview of this work and
some of its principal findings and models.
References
6.1
C.R. Southwell, J.D. Bultman, C.W. Hummer: Estimating service life of steel in seawater. In: Seawater
Corrosion Handbook, ed. by M. Schumacher (Noyes
Data Corp., Park Ridge 1979) pp. 374–387
6.2
J.M. Wright, A. Colling, G. Bearman: Open University:
Seawater: Its Composition, Properties and Behaviour
(Butterworths-Heinemann, Oxford 1995)
6.3
H.U. Svedrup, M.W. Johnson, R.H. Fleming: The
Oceans: Their Physics, Chemistry and General Biology (McGraw-Hill, New York 1942)
6.4
B.J. Little, J.S. Lee: Microbiologically Induced Corrosion (Wiley, New York 2007)
6.5
OSPAR: Regional Quality Status Report II for the
Greater North Sea (OSPAR Comm., London 2000)
6.6
H.A. Cole: Pollution of the sea and its effects, Proc.
R. Soc. B 205(1158), 17–30 (1979)
6.7
A.M. Szmant, A. Forrester: Water column and sediment nitrogen and phosphorous distribution patterns in the Florida Keys, Coral Reefs 15, 21–41 (1996)
6.8
M.J. Furnas, J. Brodie: Current status of nutrient levels and other water quality parameters in the great
barrier reef. In: Downstream Effects of Land Use, ed.
by H.M. Hunter, A.G. Eyles, B. Rayment (Department
of Natural Resources, Queensland 1996) pp. 9–21
6.9
J.M. Odom: Industrial and environmental activities of sulfate-reducing bacteria. In: The SulfateReducing Bacteria: Contemporary Perspectives, ed.
by J.M. Odom, R. Singleton Jr. (Springer, New York
1993) pp. 189–210
6.10 G. Radach, J. Genkeler: Gridding of the NOWESP Data
Sets, Ber. Zent. Meere. Klimatforsch. B: Ozeanogr.,
Vol. 27 (Inst. Meeresk., Hamburg 1997)
6.11 A.F. Carlucci: Nutrient and microbial response to nutrients in seawater. In: Effect of Ocean Environments
on Microbial Activities, ed. by R.R. Colwell, R.Y. Morita
(Univ. Park Press, Baltimore 1974)
6.12 K.H. Coale, K.S. Johnson, S.E. Fitzwater, R.M. Gordon, S. Tanner, F.P. Chavez, L. Ferioli, C. Sakamoto,
P. Rogers, F. Millero, P. Steinberg, P. Nightingale,
D. Cooper, W.P. Cochlan, M.R. Landry, J. Constantinou, G. Rollwagen, A. Trasvina, R. Kudela: A massive
phytoplankton bloom induced by an ecosystemscale iron fertilization experiment in the equatorial
pacific ocean, Nature 383, 495–501 (1996)
6.13 B. Austin: Marine Microbiology (Cambridge Univ.
Press, Cambridge 1988), Chap. 5
Part A | 6
The marine environment is, nevertheless, severe for
concrete structures. Under suitable conditions, the chlorides in seawater can combine with the ferrous ions
released by the steel reinforcement in the corrosion
process to produce highly soluble ferrous chlorides
(FeCl 2 ), and with the sufficient availability of oxygen, very soluble ferric chloride ions (FeCl 3 ). These
can leach out of concretes very readily and leave
merely brown watery-looking rust stains rather than the
usual build-up of solid rust products responsible for
cracking, such as shown in Fig. 6.11. The corrosion
associated with FeCl 2 production can be very severe.
Figure 6.12 shows a case where apparently sound concrete, some 65 years old, without any visible external
rust staining or cracking was broken open as part of
a routine scientific investigation. It revealed almost
complete loss of about 300 mm length of reinforcement bars inside the concrete. Only some magnetite
(the black material) was left to show the location of
the bar. Figure 6.13 shows the severely corroded end
of the bar, that some small distance away, was left intact within the adjacent concrete [6.52]. Several other,
similar cases have are now available, some in summary form [6.55, 56] and detailed investigations are
proceeding. Finally, the marine environment can also
be a problem for the concrete itself [6.16, 17], but
modern practices largely have eliminated this as an
issue.
These observations show that reinforced concrete
can be a very successful construction material in marine
environments, provided a high level of alkali material
is embodied in the concrete mass, giving long-term
buffering against alkali loss through leaching. However,
it is possible for severe localized corrosion loss of reinforcement to occur without obvious external warning
signs. This latter aspect is currently under urgent investigation as the implications for existing reinforced
concrete infrastructure as significant.
6.8 Conclusion
Seawater is a complex mix of many different chemicals
and microorganisms, even though it is remarkably uniform for most parts of the world. It is usually considered
to be a hostile environment for materials and this is evident in the research efforts devoted to understanding the
initiation of corrosion and its propagation once it starts.
The present chapter has outlined some of the current
research in this area, focusing mainly on engineering
rather than purely scientific investigations. The research
is driven largely by the needs of industry but anchored
in fundamental science and the basic understanding of
the processes involved. It is focused on developing tools
and techniques that can be applied in the offshore, shipping, and coastal environment engineering industries.
The present chapter gives an overview of this work and
some of its principal findings and models.
References
6.1
C.R. Southwell, J.D. Bultman, C.W. Hummer: Estimating service life of steel in seawater. In: Seawater
Corrosion Handbook, ed. by M. Schumacher (Noyes
Data Corp., Park Ridge 1979) pp. 374–387
6.2
J.M. Wright, A. Colling, G. Bearman: Open University:
Seawater: Its Composition, Properties and Behaviour
(Butterworths-Heinemann, Oxford 1995)
6.3
H.U. Svedrup, M.W. Johnson, R.H. Fleming: The
Oceans: Their Physics, Chemistry and General Biology (McGraw-Hill, New York 1942)
6.4
B.J. Little, J.S. Lee: Microbiologically Induced Corrosion (Wiley, New York 2007)
6.5
OSPAR: Regional Quality Status Report II for the
Greater North Sea (OSPAR Comm., London 2000)
6.6
H.A. Cole: Pollution of the sea and its effects, Proc.
R. Soc. B 205(1158), 17–30 (1979)
6.7
A.M. Szmant, A. Forrester: Water column and sediment nitrogen and phosphorous distribution patterns in the Florida Keys, Coral Reefs 15, 21–41 (1996)
6.8
M.J. Furnas, J. Brodie: Current status of nutrient levels and other water quality parameters in the great
barrier reef. In: Downstream Effects of Land Use, ed.
by H.M. Hunter, A.G. Eyles, B. Rayment (Department
of Natural Resources, Queensland 1996) pp. 9–21
6.9
J.M. Odom: Industrial and environmental activities of sulfate-reducing bacteria. In: The SulfateReducing Bacteria: Contemporary Perspectives, ed.
by J.M. Odom, R. Singleton Jr. (Springer, New York
1993) pp. 189–210
6.10 G. Radach, J. Genkeler: Gridding of the NOWESP Data
Sets, Ber. Zent. Meere. Klimatforsch. B: Ozeanogr.,
Vol. 27 (Inst. Meeresk., Hamburg 1997)
6.11 A.F. Carlucci: Nutrient and microbial response to nutrients in seawater. In: Effect of Ocean Environments
on Microbial Activities, ed. by R.R. Colwell, R.Y. Morita
(Univ. Park Press, Baltimore 1974)
6.12 K.H. Coale, K.S. Johnson, S.E. Fitzwater, R.M. Gordon, S. Tanner, F.P. Chavez, L. Ferioli, C. Sakamoto,
P. Rogers, F. Millero, P. Steinberg, P. Nightingale,
D. Cooper, W.P. Cochlan, M.R. Landry, J. Constantinou, G. Rollwagen, A. Trasvina, R. Kudela: A massive
phytoplankton bloom induced by an ecosystemscale iron fertilization experiment in the equatorial
pacific ocean, Nature 383, 495–501 (1996)
6.13 B. Austin: Marine Microbiology (Cambridge Univ.
Press, Cambridge 1988), Chap. 5