Corrosion Survey & feasibility study for Cathodic Protection in Channel ports



The FLIP study reviews the state of cathodic protection in the port of Tor bay.  The study recomends a number of techniques to achieve cathodic protection against Accelerated Low Water Corrosion (ALWC). However, the study found that the size of anodes required were presently not sufficient , especially in the relatively shallow depths at low water in front of this harbour structures to polarize.  This was a common theme in the ports of Torquay and Brixham where sacrificial anodes should be fully submerged at all states of tides (especially MLWS) if the anodes are to have the desired effect.  In four of the six cases investigated by the FLIP study in Tor Bay, cathodic protection (CP) was found to be efficient and feasible solution subject to the anodes being of sufficient size.  Useful advice is given on the location of these anodes to prevent them from wear from the sea and currents. The study therefore recommends new larger galvanic anodes to be installed in the near future. Of the remaining investigated by the study, and interesting to other Channel ports, CP was not considered to be appropriate.

One approach involve a mix of solutions.  In one case where at the the lower level quay wall concrete props are located below the mid tide level it was found that these could be protected by cathodic protection using similar galvanic system to those recommended for the immersed steel piles. This would minimise costs and the extent of works required below mid tide on the concrete props. For the sections above mid tide, an impressed current system could be designed to provide the necessary protection. However, an important conclusion recahed by this study, and relevant to other small and medium sized ports in the Channel region investigating similar solutions, it is essential to take account of the size and an individual pier of quay structure before opting for an impressed current cathodic protection system as it has a relatively high cost for the benefit gained.

In addition impressed current systems that may be considered for the props require cables to be routed from the protected structure back to a power supply unit in an accessible location. Any such cabling used for the protection of the props would require to be run in cable management mounted on what appears to be already severely corroded atmospherically exposed steel framework. 

The study recommends an alternative more cost efficient approach, particularly to harbour structures that have suffered from significant damage. This approach involves the removal all concrete surrounds to the steel beams of the pier.  Providing this is does not compromise the required structural capacity of the Pier (subject of additional surveys in  Tor Bay), the remaining steel can be blast cleaned before applying a market recognised high specification coating system.

Download the full studies below