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Impressed
current cathodic protection (ICCP) systems consist of
an anode system, a DC power supply and monitoring probes,
with associated wiring as with other cathodic protection
systems. For steel in concrete, one of the most important
decisions is the choice of anode.
Anodes
consist of:
- conductive
coatings on the surface (conductive organic coatings,
thermal sprayed zinc or titanium)
- mixed
metal oxide coated titanium mesh or ladders in a concrete
overlay
- conductive
mortar overlays
- coated
titanium ribbon in slots
- conductive
ceramics or mixed metal oxide coated titanium rods
or tubes in holes in the concrete
The
range of anodes means that the technology can be adapted
for application to most situations. There is extensive
literature on the subject as well as national and international
standards and specifications. ICCP has been applied
to most types of reinforced concrete structures, such
as:
- Buildings
(blocks of flats, offices, hospitals, schools etc.)
- Bridges
(decks and substructures)
- Tunnels
- Wharves
and jetties
- Water
towers
- Industrial
plant
- Multistorey
car parks
It
is primarily applied to structures suffering from
- Cast
in chlorides (contaminants or calcium chloride admixture)
- Sea
salt ingress on marine structures
- Deicing
salt on highway structures
- Historic
steel framed, stone clad structures
Cathodic
protection stops the corrosion process across the whole
of the area where anodes are applied. It is extremely
versatile and is not limited by the extent and severity
of corrosion, as long as anodes can be placed in a suitable
electrolyte for the current to pass to the corroding
steel areas.
Using
cathodic protection:
- minimises
the amount of break out for patch repairs
- smaller
cut outs may alleviate the need for structural propping
during patch repairs
- minimising
patch repairs minimised the disturbance to occupants
of offices, blocks of flats etc.
- provides
continuous information showing that the system is
protecting the structure
- is
frequently the most cost effective solution on a whole
life cost analysis
- provides
protection regardless of chloride levels
- Can be provided with insurance backed warranty
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