Hybrid corrosion protection of a prestressed concrete bridge

The Kyle of Tongue Bridge in Sutherland, Northern Scotland opened in 1970, has an overall span of 184m of 18 approximately equal spans and carries a single lane dual carriageway. The bridge was repaired in 1989 due to chloride induced corrosion. However, inspections from 1999 onwards reported on-going corrosion and structural deterioration. A refurbishment contract was let in 2011 to extend the service life of the structure for a 20 year period by providing corrosion arrest and prevention. This paper describes how hybrid corrosion protection was used to offer protection to the prestressed concrete beams of the bridge. The results indicate that hybrid anodes provide an attractive alternative to other corrosion protection systems as they can be targeted to specific areas of need. They offer a temporary energising phase to arrest corrosion, followed by a permanent galvanic mode phase which is particularly beneficial for prestressed concrete structures in order to reduce the risk of hydrogen embrittlement.