Mr. Peter Robinson: To ask the Secretary of State for Transport what research was undertaken on the impact of corrosion fromde-icing chemicals on the bridge bearings of the Thelwall Viaduct on the M6 at the design stage; and what research has beenundertaken since into alternative technologies that could reduce the levels of corrosion. [118096]Mr. Jamieson: The risk of corrosion from environmental pollutants including de-icing chemicals on Thelwell Viaduct was minimised byusing stainless steel and provision of enclosures (skirts) around the steel roller bearings. The majority of the bearing locationsdo not have expansion joints at the road level, thus reducing the risk of surface water and de-icing salts reaching the surfaces ofthe roller bearings.The effectiveness of non-corrosive de-icing agents has been researched over many years in UK and other countries. There arelimitations on their effectiveness at low temperatures and the use of rock salt is then necessary. Such agents are used in the UK onsome major bridges where the higher cost can be justified in whole life terms.