The NTSB report on the Fern Hollow Bridge collapse in Pittsburg made the remarkable assertation that "rust makes metal weaker".
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It seems that the State of Washington has been conducting a peer review test of this assertation, and has independently confirmed that indeed rust does make metal weaker.
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Pittsburgh bridge collapse - Engineering Failures & Disasters
thread815-491466 NTSB to other bridge owners: "Rust makes metal weaker." https://www.cbsnews.com/pittsburgh/news/ntsb-fern-hollow-bridge-report-review-bridge-inspection-reports-nationwide/

It seems that the State of Washington has been conducting a peer review test of this assertation, and has independently confirmed that indeed rust does make metal weaker.

SR 165 Carbon River Fairfax Bridge Closure
The State Route 165 Carbon River Fairfax Bridge closed April 14, 2025, after inspections revealed new deterioration of steel supports on the 103-year-old structure.