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Cathodic protection design and installation


Cathodic protection (CP) is added to steel structures to help

prevent or slow the rate of corrosion. Within the maritime

environment this is a common means of improving the durability

of structures. 

Cathodic protection systems will either be a sacrificial or active

CP system. A sacrificial system will work by placing metals with

higher electro-potential than steel next to the structure and then

ensuring the two metals are electrically coupled. The sacrificial

metal then takes the role of anode in the electro-chemical


Constructex has worked with its clients to install cathodic

protection systems to a variety of structures, including: sheet

pile walls, bearing piles, jetties, vessels and boat hoists. 

Anodes will typically be installed below lower water level

(although sometimes the seabed will not permit this - as shown

in the adjacent picture). The anode will ideally then remain

submerged at all states of tide. The anode will help protect the

steel within the intertidal zone and the submerged zone. The

intertidal zone area will still sufffer from corrosion and the area

above the tidal zone will require separate protection by other

means (e.g. a coating system).

Sacrificial anodes will have a design life and will then need to be replaced. It may be possible to reuse the existing fixing brackets which, if well designed, can reduce the cost of installation.

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