Protection of Steel Bridges from Corrosion

Abstract

Atmospheric corrosion is only one of many causes of deterioration of structures, and protective measures applied to bridges are usually successful, in the sense that disasters resulting from corrosion are rare. Most bridge steelwork requires careful protection and regular inspection and maintenance, though in certain circumstances various grades of steel can be left uncoated. Depending on the intended life of a bridge, the procedure which in the long run is the most economic is usually one which employs a high standard of initial protection, so that unnecessarily frequent repainting is avoided. The circumstances in which steel piles can safely be used to support a bridge structure are briefly discussed. The protection of superstructure steelwork begins at the design stage, when much can be done to minimise subsequent corrosion troubles. Guidance is given on the choice of protective films, with or without a preliminary coating of non-ferrous metal. The standard of surface preparation needed for each type is given and its importance emphasised. The advantages of carrying out part of the protective work at the factory are explained, and special points to be considered at joints, bearings and road decks are described.

Maintenance painting is needed between 10 and 20 times during the life of a steel bridge, and calls for careful attention backed up by regular, skilled and painstaking inspection. A good system of testing is needed, and simple tests giving quick results have distinct advantages, especially if they can be carried out at the site where painting is being done. Some actual examples of protective measures adopted on a variety of modern steel bridges are described.