OldCADuser wrote:
Note that there some types of steel are formulated to be installed unfinished, and then allowed to rust. Now unlike most other common steels and iron, the rusting process halts after a period of time and the underlying metal is protected from further deterioration. This is engineered to work similar to the natural oxidation process seen with materials like aluminum and copper. One of the advantages of this is that over the life of the structure, there is very little maintenance required, like painting, which generally requires that the old paint, and any rust, has be removed first. Now this material is significantly more expensive and is generally only used for smaller structures, or where long-term maintenance would be difficult or expensive to perform. It's also used when there's a desire for a certain aesthetic appearance, which might have been the case with this bridge.
Note that there some types of steel are formulated... (
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I believe that steel is called Corten Steel.