Sacrificial anodes for harbours
Unprotected sheet piling and tubular support piles are experiencing rapid corrosion and failing well within their intended design life.
The most prevalent solution for cathodic protection of harbours is to install sacrificial anodes, also called galvanic anodes. Most commonly used are aluminium alloyed anodes, but in low salinity water (brackish water) magnesium anodes with higher driving voltage may also be applied.
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Aluminium anode alloy has an electrochemical capacity of about 2500 Ah/kg, depending on the compositon and production method. Current output capacity for harbour anodes is typically between 2 and 3 A each, with a driving voltage in the range 0.25 to 0.3 V. Capacity of aluminium anodes from Cathwell.
To ensure effective, economical and durable corrosion protection, a proper design must be performed, where several parameters are involved. Design of cathodic protection system for harbours.
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Sacrificial anodes are evenly distributed on the structure to be protected, and mounted with continuous, persistent metallic contact. The anodes are typically designed for a corrosion protection lifetime of 20 to 30 years.
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Allowance for metal loss
It is generally most rational that sheet piles are designed for being cathodically protected on the sea side, but dimensioned with allowance for metal loss on the shore side.