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Control of corrosion of underwater piles
1. CONTROL OF
CORROSION OF
UNDERWATER PILES
Presented by:
Avinash Shaw
Roll no. 11/CE/45
Department of Civil Engineering
NIT Durgapur
2. Introduction
Corrosion is the destruction of metals and
alloys by the chemical reaction with the
environment.
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
eliminate corrosion.
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 occurs 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
8. 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
9. 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
10.
11. 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
12. 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
13.
14. 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
PHASE 1
PHASE 2
PHASE 3
15. 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
16. 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
PHASE 1
PHASE 2
PHASE 3
18. Protective Coating
In order to protect metals from corrosion, the
contact between the metal and the corrosive
environment is to be cut off. This is done by
coating the surface of metals with a
continuous non-porous material inert to the
corrosive atmosphere.
Surface coatings are broadly classified into
three
Metallic coatings
Inorganic Coatings
Organic Coatings
20. • arrest rust creep, or undercutting
of the coatings surrounding the
damaged area
• high degree of resistance to heat
and chemical spills
Inorganic
Zinc
Silicates
Primers
21. • Epoxies are generally more
abrasion and chemical resistant
than primers
• These are poor resistance of ultra
violet from sunlight and most will
chalk and fade rapidly.
High
Build
Epoxy
Coating
s
22. • optimum resistance to UV and high degrees of
flexibility and chemical resistance.
• maintain a very high level of cosmetic gloss and
color retention and can be cleaned very easily
with low pH detergents and fresh water pressure
washing.
Aliphatic
Polyuret
hane
Topcoats
23. • high level of service and are more
tolerant to compromised surface
preparation and ambient weather
conditions
• maintaining damaged areas and
breakdown of the coatings systems
Zinc Rich
Epoxy
Primers
24. • normally incorporate very course
aggregates for an exaggerated
profile.
• They are applied in very high film
builds and normally without a zinc
rich primer.
Non-Skid
Deck
Coatings
25. 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.
26.
27. • These are similar to the cathodic
protection method in philosophy.
• These are designed on the design basis
of maximum current distribution for the
lowest possible cost, with the most long-term
reliability.
30. 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.
31. 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.
32. • 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
33. 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.
Bi-directional material is the best option.
Scaffolding measures during the application of
