Client: Australian Maritime Safety Authority (AMSA)
Consultant: Infracorr Consulting
Contractor: Marine and Civil Maintenance Pty Ltd
Date – September 2013
Cape Don Lighthouse is located on the Cobourg Peninsula, Northern Territory, and was constructed in 1917 to service the passage between the Cobourg Peninsula and Melville Island en route to Darwin.
The Structure is approximately 30m tall and the concrete was suffering from significant chloride induced spalling due to the original construction methods of using beach sand and local materials.
The lighthouse is a critically important structure in a very remote location and subjected to extreme environmental conditions.
Infracorr Consulting considered several options for repair. A cost effective and appropriate design was prepared, which took into account the isolated site, a requirement for a long system service life, and the need for low monitoring and maintenance.
In conjunction with concrete patch repairs and protective coatings, the Hybrid CP system was chosen to provide the long term protection to the lighthouse.
The Hybrid CP system utilizes zinc alloy anodes installed into drilled holes, with the anodes initially powered using a small power supply. The high initial current passivates the reinforcement, restoring the alkaline (high pH) environment to the concrete. Following this initial phase, the power supply and temporary cables are removed, and the anodes are then connected to the reinforcement to provide ongoing galvanic protection.
Marine and civil are specialist contractors and completed all the rehabilitation requirements and installation of the Hybrid system. Access was a critical aspect on this project and was designed by the contractor. All equipment was transported by boat as this is the only access to the island.
Hybrid Duoguard cathodic treatment was adopted over traditional ICCP primarily as it is very suited to such an isolated site location and not reliant on a permanent power source. Additional benefits included significantly reduced requirements for monitoring and maintenance and hence major savings in the associated costs.
The repair works are designed to provide an additional 50 years of life to the structure.