Stainless bridges

The state of Oregon in the NW USA is using S32205 stainless steel to build a bridge designed to last 120 years, according to Virginia Heffernan (Nickel magazine, February 2003). This is an attempt to overcome the corrosion problems that plague some of the older bridges along the Pacific coastline. The USD 12 million bridge now under construction over an estuary near Coos Bay will contain 363 tonnes of stainless steel rebar, believed to be the largest quantity of stainless steel used for any bridge in North America.
The Oregon marine environment is hard on bridges reinforced by carbon steel rebar, owing to the salty, moist air. To prevent these problems, designers usually recommend S31653 or S30400 stainless steel. But Oregon has chosen the S32205 alloy, which has much greater corrosion resistance, hoping to extend the maintenance-free life of the bridge to 120 years while providing the structure with enough strength to withstand potentially damaging seismic activity in the earthquake-prone area. The S32205, supplied by Carpenter Technology Corp., contains 22% chromium, 5.5% nickel and 3% molybdenum. The balance is made up of iron and smaller quantities of silicon, carbon, phosphorous, sulphur and nitrogen.

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