Corrosion of steel foundation caissons from the old Redheugh Bridge in Newcastle upon Tyne

Abstract

With particular emphasis on underground exposures because of their relevance to steel foundation structures, the total thickness loss corrosion rates, together with some chemical and metallurgical test results, were obtained from an examination of two old Redheugh Bridge steel foundation caissons recovered after 89 years’ service in a tidal section of the River Tyne. Below river bed level, the general and pitting corrosion rates were measured to be a maximum of 0·015 and 0·04 mm/year respectively. Above bed level, corrosion was greatest in the low water zone at 0·04 mm/year, but at higher levels the caissons remained variably protected by remnants of a thick tar coating. The corrosion findings are in good agreement with those published for steel pile corrosion. In respect of the measured underground corrosion rates, these, combined with the. generally accepted maximum working stress levels of between 30 and 50% of the yzeld stress, should enable economic steel foundation structures to be designed with working lives well in excess of 100 years.