Any time I’ve seen train tracks, even brand new ones, they always have that rust color. True, the top surface, where the wheels come into contact, is usually silvery grey, but the underlying parts are always rust red. Why is this? Do they “pre-oxidize” the steel at the factory, and if so why do they do it?
Or do they buy old tracks from railroads that are being discontinued, and use those?
Are you sure it isn’t paint?
The rails are made of steel. And steel rusts. :smack:
They probably were rusted by the time they were delivered to the railroad from the manufacturer.
The rails rust pretty quickly. If you saw freshly laid track that was already rusty, it was probably salvaged from somewhere else and re-used. Even brand new rails usually sit around the railyard for a while before being laid and have plenty of time to build a thin layer of rust.
I’m a model railroader and painting the sides of the rails a rust color is tedious, but much more realistic looking.
Just a WAG, but I’m guessing that the train tracks are cast iron. When cast iron oxidizes, it gets a thin layer of rust on the surface, but that’s it. Steel will continue to rust all the way through and need some kind of a surface treatment to keep that from happening.
So, if they are made from cast iron, the surface rust is no big deal so they don’t do anything to stop it from happening.
I imagine this must be the answer.
Rail rusts very quickly. It needs to be strong, not pretty. Many years ago, there was a train strike near my home, and the tracks went from shiny silver on top to rust brown in three days.
It’s made from high-carbon steel. Cast iron would be too brittle.
Yep, steel was taking over by the mid-19th century.
My WAG is that physical wear from contact with wheels, and fracturing, dictates the lifespan of the rail long before rust has a significant impact.
Even though steel rusts, some types evidently are made to only develop a surface layer, that then acts as a sort of protective layer for the rest. This is done deliberately, so that you can put massive steel objects out in the unprotected outdoors and not have to keep coating it, cleaning it, or painting it. But on many cases, it looks like hell.
One example is the University of Utah’s “Fly’s Eye” Cosmic Ray observatory out in the salt desert near the Dugway Proving Grounds. The individual detectors are placed in galvanized cylinders supported by such deliberately rusted supports. The rust also runs down the sides of the cylindrical containers. It looks like the world’s largest Garbage Can Farm.
By the way, the Wikipedia article to the contrary notwithstanding, the facility was in operation well before 1999, by the mid-1980s
CalMeacham pretty much has it.Track “iron” is a maganese steel with about a point of carbon,and develops a protective layer.Not quite Cor-Ten in corrosion resistance,but meets requirements for work hardening,spalling,etc.
I used to work at a place that used crane rails (think railroad tracks upside down supporting an indoor overhead crane, or roller coaster tracks) as the track for a rocket sled. Every time we’d run a test, the rust would be worn away where the pads contacted the track. When we went back to the site, there was always a thin layer of rust on the track again. Sometimes it would take up to a week, but it could happen overnight if it was humid.
Generally, rusty rails are new rails. That is to say, old disused rails are rusty too, but they are also dirty, so they are a dark, dirty brown colour. If you see a brighter burnt orange colour, you’re looking at new track.
Railways do use hand-me-down secondhand rail, but generally only on branch or secondary lines. These are traditionally laid with lightweight rail* (disparagingly called “knitting needles” by railwaymen), and only gain the heavy grade stuff when it is discarded by the important routes that carry fast, heavy trains. Now, if you see beautiful shiny rails with no rust at all on them, then those rails are actually old and probably due for replacement or at very least re-profiling with a grinder. New rail will appear rusty except for a shiny, bright ‘contact strip’ down the centre. This is because rail head is convex, and the wheels won’t touch the sides of new rail. Over time, the rail gets pounded into a flatter profile, and the entire thing looks shiny. It then needs to be profiled round again, to improve the rolling resistance of the wheels.
*In the steam days, if you had a locomotive that spent its time travelling the branchlines on thin rails, and it had to come into the city on a rare visit for maintenance of some sort, often the crew would find problems with wheelslip. The loco had developed a condition called “hollow wheels” from years of riding on thin rail, and now back on wider rail, it was having trouble with adhesion.