Experimental study into the corrosion of buried metal coupons

The report provides details of a field study, initiated in 1976, to investigate the rates of corrosion of both coated and uncoated metal coupons buried in London Clay and Bramshill Sand. Coupons were exhumed from the soils in 1978 and in 1990 and the measured rates of corrosion are compared to the current DOT requirements for reinforced soil structures and corrugated steel buried structures. Tensile tests were also undertaken on a number of coupons, and for reinforced soil applications it would seem appropriate to express the severity of corrosion in terms of the loss in tensile strength. The data do not justify any changes to the existing Department of Transport (DOT) requirements for galvanized mild steel strips used for such applications. The data support the view that aluminium alloys and uncoated mild steels may not provide adequate service when used for reinforced soil applications. The existing DOT requirements for buried metallic conduits seem adequate, but in-service performance may not be satisfactory where pitting attack is promoted by, for example, the presence of chloride ions. (A)