1. CONTROL OF CORROSION ON
UNDERWATER PILES
Submitted to: Submitted by:
Dr . J.K. Sharma Poonam Shekhawat
Asso. Professor (09/264)
Department of Civil Engineering
University College of Engineering
Rajasthan Technical University, Kota
2. Corrosion is the destruction of metals and alloys by the
chemical reaction with the environment or it may be regarded
as the reverse process of extraction of metals from ore.
Generally many traditional metal parts are used with lighter
polymeric components but these are impervious to
electrochemical corrosion so even with the proper selection of
base metals, there is no absolute way to eleminate corrosion.
Forms of corrosion protection include the use of inhibitors,
surface treatments, coatings and sealants, cathodic protection
and anodic protection.
3.
4. On steel piling in seawater, the more chemically active
surface areas (anodes) are metallically coupled through
the piling itself to the less chemically active surface areas
(cathodes) resulting flow of electricity and corrosion of
anodic areas.
Generally corrosion occures when local anodic and
cathodic areas continually shift about randomly but
sometimes they do not shift position end, therefore the
metal suffers localized attack and pitting occurs.
In general smaller the anode area relative to the cathode
area, the deeper the pitting
5. CORROSION CAUSED BY THE
DIFFERENCE OF THE DISSOLVED
OXYGEN (DO) CONCENTRATION
6.
7. SPLASH
ZONE
ZONES
ATMOSPHERIC
ZONE
SUBMERGED
ZONE
TIDAL
ZONE
Depending upon
time of wetness,
temperature,
pollutants etc.
Atmospheric
corrosion is
responsible for a
large fraction of the
total corrosion in the
world.
CORROSION
RATE(without
protection)
< 0.1 mm/year
8. SPLASH
ZONE
ZONES
ATMOSPHERIC
ZONE
SUBMERGED
ZONE
TIDAL
ZONE
The splash/spray
zone can be
characterized by as
an aerated sea
water environment
Where exposed
material are almost
continually wet and
biofouling do not
attach.
CORROSION
RATE(without
protection)
0.3 mm/year
9. SPLASH
ZONE
ZONES
ATMOSPHERIC
ZONE
SUBMERGED
ZONE
TIDAL
ZONE
The tidal zone is an
environment where
metals are
alternately
submerged in
seawater and
exposed to the
splash zone as the
tide fluctuates.
CORROSION
RATE(without
protection)
0.1-0.3 mm/year
10. SPLASH
ZONE
ZONES
ATMOSPHERIC
ZONE
SUBMERGED
ZONE
TIDAL
ZONE
The
submerged/shallow
ocean environment
zone usually
characterized by
well aerated water
combined with
marine biofouling
organism of both the
plant and animal
variety.
CORROSION
RATE(without
protection)
0.1-0.2 mm/year
11. Phase 1 of the program is
the programmatic
assessment or planning
stage of the project.
For the planning
stage,three main
requirements sought,
budget and schedule
needed to overcome the
problem raised from
corrosion of
reinforcement.
PHASE 1
PHASE 2
PHASE 3
12. Phase 2 of the program
involves physical
assessment and actual
remediation.
Inspections for severity of
corrosion are conducted
in this phase to determine
what strategy or methods
are most suitable to be
applied.
PHASE
1
PHASE
2
PHASE
3
13. Phase 3 of the program
mainly deals with future
monitoring of the repaired
structure.
Systematically identifying
and managing the
existing resources can be
done by implementing
internal or external
monitoring system using
current technology.
PHASE 1
PHASE 2
PHASE 3
16. CATHODIC PROTECTION
Cathodic protection is an electrochemical process
which halts the corrosion of metals in a particular
environment by superimposing an electrochemical
cell more powerful than the corrosion cell.
Sacrifical Anodes are fitted or bonded to the metal
to be protected.
The implementation is simple, all you need is an
anode, a power supply and engineering talent.
19. APPLICATION OF FRP
COMPOSITES
The poor durability of conventional corrosion
repairs has led to increased interest for its
replacement by fiber reinforced polymers.
Although dry conditions are favorable but
availability of resins that can cure in water has
made it possible.
Saturating FRP with resin and installing is complex
but benificial in costly repairs and rapid
deterioration.
20. Fibre reinforced polymers have
long been used for the repair
and retrofit of concrete
structural elements.
Lightweight, high strength and
resistance to chemicals.
Unparallel flexibility, multi-directional.
Twofold role: first to restore lost
flexural capacity and second to
provide resistance to withstand
expansive forces.
21. Figure shows impact damage
that led to both cross-section
and breakage of the spiral ties.
Using FRP there is only need to
re-form the cross-section and
apply bi-directional layers to
restore lost tensile capacity.
Bonding agents may be
required to assure capillary
suction of the epoxy and to
ensure good bond.
22. Though there is no absolute way to eliminate all
corrosion on underwater piles, there are some
effective measures to control them.
Cathodic protection is quit simple and protective
coatings are used in vast and expensive structures.
The FRP composites have many advantages viz.
lightweight, posses high strength and chemical
resistance and moreover have incomparable
flexibility.
Of the various ways of wrapping of FRP composites
, transverse wrapping is found to be the easiest.
