Corrosion Protection of Steel Highway Bridges: II Characterisation of bridge locations by corrosion and environmental measurements

Abstract

Climatological and air pollution factors greatly affect the corrosion damage to steel highway bridges. This paper gives first results of a programme to define quantitative criteria by which the potential corrosivity of a prospective bridge location can be assessed.

At seven sites throughout the country, the corrosion rates of a special mild steel, a low alloy steel and zinc are being measured under both open and sheltered exposure conditions. Meteorological and air pollution data are also being collected.

To eliminate the considerable delays which can occur in negotiating the building of permanent test compounds, a mobile test rig has been developed, which can be easily transported to any prospective bridge location.From the first year's results, it is apparent that sheltered test specimens give a much closer indication of the corrosivity under a bridge deck than do open exposure specimens. Of the environmental factors, atmospheric chlorides and sulphur compounds are the major factors influencing corrosion rate. It was not possible, at this stage of the work, to produce a correlation between corrosion rates and meteorological data.