Rust is bad when it causes the steel walls of freight cars to buckle.
Rust can be unavoidable when steel parts can not be painted for safety purposes.
Where is a coating of rust a must that makes steel better?
Andrew Falconer
Rust never sleeps.
CorTen
Rust - the poor mans Loctite.
If you happen to have hydrogen sulfide on hand and want to start a pyrophoric reaction, rust comes in handy.
Rotten Eggs + Rust = Fire ??? Who knew !! But don’t tell the terrorists. And please, don’t tell the TSA, either, or next we’ll be searched for eggs and any steel items at the airports !
CorTen = US Steel’s trademark for a 1960s steel that when it rusts, the rust seals the surface as a protective layer against further corrosion. The selling point is that it never needs painting, and the rust is a supposedly pleasing “earth tone” color. [:-^] It’s self-healing - if the rust is scraped away, it rusts again to re-estabish that layer. Since it’s been around for like 40 years now, it would be interesting to see a study of how it has actually perfomed in service.
- Paul North.
There are some bridges I have seen where they leave then completely unpainted and say a think coating of rust protects the steel underneath…we have one near my home in Illinois.
Those bridges are constructed with “weathering” or “self-protecting” steel of which USS’s Cor-Ten steel is an example. Technically these are known as ASTM A242 or A588 steel. The rust coat is actually very thin.
Self-weathering steel has been used in bridges in the U.S. since 1964. Review of results in bridges is that it has performed well and has been cost-effective compared to the alternative (painted steel or alloy steel) with the exception of Detroit.
RWM
It makes it better if it avoids the cost of painting.
RWM
Jim -
That’s most likely Cor-Ten. See the Wikipedia article on “Weathering Steel” at:
http://en.wikipedia.org/wiki/Weathering_steel
BNSF’s Latah Creek Bridge in Spokane, Washington was newly built out of a weathering steel in the mid-1970s as one of the first post-merger line consolidation and improvement projects. See the 2 photos of it on the “Marshall Creek Railfan Guide” webpage, at about 1/4 of the way down that page, at:
http://www.icehouse.net/funnelfan/marshalc.htm
Surprisingly, in skimming down the Wikipedia article I found this other railroad connection for Cor-Ten, which I hadn’t known (or remembered):
"COR-TEN was used by St. Louis Car Company to build an order of electric railcars for Illinois Central Railroad in 1971. For uniformity, the next order was built to similar specs, including COR-TEN bodies, by Bombardier in 1979. The use of COR-TEN was seen as a cost-cutting move in comparison with the railcar standard of stainless steel. The durability of COR-TEN railcars did not live up to expectations, and rust holes are appearing in the Illinois Central railcars. Most of these railcars still operate out of Chicago. No other orders of railcars have been made of weathering steel. It’s also worth noting that the IC painted their COR-TEN railcars, an unusual practice for a steel designed to remain exposed. See pictures in the “external links” section. Painted weathering steel is no more corrosion-resistant than painted convent
OK, I’ll bite - why not Detroit ?
I can’t think of any environmental factor that would be significantly different from, say, Chicago, Toledo, Cleveland, Buffalo, Toronto, Hamilton, etc.
Detroit sits on top of a salt mine (now closed) and they use the stuff very liberally during the winter. That white stuff on the street in February is not snow but SALT. I think they did that to keep the auto industry in business.
Phil
Well, then, that explains Syracuse, too. In fact the township just north of the city is Salina…
On a technical note about CorTen and the like, I’d think that perhaps sheetmetal might be too thin to really take advantage of the properties. Bridge beams are pretty hefty - an eighth of an inch of such rust doesn’t amount to much.
An eighth of an inch into sheet metal is a hole straight through.
My first experiences with the stuff were structures at our college, built in the mid-1960s. I think the metal portions of the bridges performed like they should, and the buildings that had the steel as trim (the rest of these buildings were poured concrete) still look pretty good. However, our science building was completely sheathed in the stuff, and looked terrible (the rust would flow down and cover the windows, among other things). This building wound up being completely enclosed in a newer, larger science center.
Some of the pigments or coloration of the rust from Cor-Ten and similar weathering steels will also be carried along in rainwater runoff. When it first started being used, no special provisions were made for that, and the runoff that just dripped onto the concrete piers under bridges often stained them, which kind of ruined the aesthetics - a solid dark red or brown color bridge on top of white or gray piers heavily weathered with rusty streaks.
The “fix” for that was to collect the all the runoff at the top of the piers and provide a positive drain for it instead, most often in a downspout. Sometimes those downspouts are just attached to the outside of the piers, but I believe that the Latah Creek Bridge has them inside the piers instead for a “cleaner” look, and maybe a little more protection from freezing than if they were left exposed. If so, I hope they’re still accessible for the inevitable maintenance repairs and clean-outs that such things often need . . . [:-^]
- Paul North.
There is a little more to the process than just exposing rust Fe2O3 to H2S. When Fe2O3 is exposed to H2S in an oxygen free environment, it forms iron sulfide (FeS), also called ferrous sulfide, which is a pyrophoric material. Once it is exposed to oxygen, the actual pyrophoric reaction takes place.
Never heard that one before-lmao!