Technology usually used on wharves and ships is being used for the first time by the Dunedin City Council, to stop a coastal bridge degenerating.
Repairs to concrete damage caused by corrosion around some of the reinforcing steel in the bridge across the Kaikorai Estuary on Brighton Rd have recently been completed and cathodic protection has been installed.
Council projects engineer Evan Matheson said the technique used a low-voltage electrical current, too weak to be sensed by human touch, to attract corrosion-causing chloride particles away from the bridge's reinforcing steel and on to sacrificial strips of zinc that would corrode instead.
That was considered a better option than placing weight restrictions on the 75-year-old bridge, and much cheaper than replacing it.
It was the first time cathodic protection had been used by the Dunedin City Council, or, he believed, on a road in the southern South IslandHe said the structural work on the bridge was complete and both lanes had been reopened.
The electrical current, sourced from overhead lines via a transformer, had been tested and would be commissioned at Labour Weekend. It is is expected to extend the life of the bridge by 25 years. The work cost about $760,000, compared with an estimated $2.5 million price tag to replace the bridge.
