Originally published at: NTSB's preliminary report on the collapse of the Fern Hollow Bridge in Pittsburgh | Boing Boing
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in case anybody was wondering “weathering steel” is an alloy that forms an iron oxide coating that remains in place and protects the underlying steel from further corrosion - a similar action to when copper turns green.
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Corrosion of many sorts happen to bridges.
When it comes to bridge design, the most common other metals that may come in contact with the steel are likely painted (bare) steel, weathering steel, and stainless steel. It would not be recommended to connect bare steel to galvanized steel, as the zinc will want to protect all of the carbon steel and the overall coating performance life will be decreased. However, if the other steel surfaces are painted or isolated with a non-conductive material, these connections will not significantly decrease the life of the galvanized coating as long as the paint or isolating materials are maintained over the coating lifetime
When connecting galvanized steel to any stainless or weathering steel, there are other considerations. Under atmospheric conditions of moderate to mild humidity, contact between a galvanized surface and a stainless steel surface is unlikely to cause substantial corrosion. However, if the surfaces are in the presence of salt water or salt water air, it would be best to electrically isolate the two metals.
Boat owners know that zinc will sacrifice itself fairly quickly. Especially in salt water.
“Over the past five winters, PennDOT has used an average of 807,766 tons of salt to keep Pennsylvania drivers moving.”
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Zinc is so altruistic.
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It’s the giving tree of metals.
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So what’s that make the sacrificial magnesium anodes then? The Jesus “eat my flesh, drink my blood” of metals?
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I wonder how long it will take the right to say that Biden arranged the collapse to help make the point that our infrastructure is in desperate condition.
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I would expect their angle to be, “See? This is what happens when you don’t let private companies operate roads and charge regressive taxes…er… I mean tolls to use them”.
The Republican strategy has been “take over government, then, destroy it to prove it doesn’t work” for decades.
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That team of inspectors has a lot of guts to be walking around beneath that collapsed structure.
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They’ll also frame the juxtaposition of the infrastructure push and the bridge collapse as “taking advantage of a tragedy to push a liberal agenda” while eliding that the agenda in question is preventing more bridge collapses and the like. Because every single thing they whinge about is projection of their own craven malfeasance.
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it’ll be fine, start another war instead.
Like Corten steel? Also used in the US Steel building in downtown Pittsburgh (now carrying UPMC’s name).
Corten is a “brand” of weathering steel.
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