Duplex Stainless Steels for Durable Footbridges

Duplex stainless steels have many desirable characteristics which can be exploited in bridge applications. They are particularly suitable wherever requirements for resistance to environmental conditions combine with the need for high load bearing capability.

Their full potential is reached in locations where the structure comes into contact with environments containing corrosive waters (salt or brackish water), where high concentrations of chlorides (salt) are present in the air or where de icing salts are used . The three grades most suitable for use in bridges are 2205 ( 1.4462 )), 2304 ( 1.4362 and LDX2101 ( 1.4162

The reason for having several duplex grades concerns both corrosion resistance and costs. Higher alloying content giv es higher corrosion resistance, but it also increases the costs. Therefore the different grades offer the possibility of a cost efficient material selection suited to the aggressiveness of the site environment.

A cost comparison study shows that the premium for using stainless steel can be minimised by careful design, material grade and choice of construction method. The results show that an optimized stainless design will come out at the same level or only marginally more costly than a standard carbon steel design.

A conservative assess ment from four scenarios shows that the maintenance of a simple bridge over a 60 year service life could be reduced significantly by using stainless steel inste ad of carbon steel . These saving can be in the range 30 40% mainly due to avoiding the need for painting associated with carbon steel structures.

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