The use of unpainted Corten B in marine bridge applications requires careful consideration. Corten B is a high-strength, low-alloy weathering steel that develops a protective oxide layer when exposed to atmospheric conditions, significantly reducing the need for painting in most environments. With a minimum yield strength of 345 MPa, it is well-suited for structural bridge applications. The material has been successfully deployed in numerous bridge projects worldwide, including the New York High Line pedestrian bridge, where annual corrosion in coastal environments measured only 0.008 mm.
However, marine environments present unique challenges. The presence of chloride ions from salt spray can disrupt the formation of the protective patina, accelerating corrosion. Research indicates that under sheltered marine conditions with limited chloride exposure, Corten B corrosion rates remain manageable. But in open, highly exposed marine settings where chlorides are abundant, the protective rust layer may fail to stabilize properly.
Industry guidance recommends that “corrosion should be monitored if an unpainted steel such as cor-ten B is used in bridge construction” in marine settings. While Corten B is specified for highway bridges and marine engineering applications, successful implementation depends on site-specific conditions: tidal zones and direct salt spray exposure are generally unsuitable for unpainted applications, whereas elevated, sheltered, or inland bridge locations with minimal chloride deposition can be viable. For marine bridge projects, a hybrid approach—using Corten B with supplemental protective measures in the most exposed zones—often provides the optimal balance of cost savings and long-term durability.
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