Why are rail brown?

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pt_mad

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Why are the railway lines brown? Are they painted brown? Must be hard to identify rust.

Also why do they allow overhead line supports to start going rusty? Isn't prevention the best strategy?
--- old post above --- --- new post below ---
Apologies for the mistake in the thread title. Should have been 'why are rails brown' :oops:
 
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ainsworth74

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It will be a combination of dirt (and not just the sort that's been suggest further up thread ;)) and rust. Completely fresh rail is just the colour of steel once it's been in place for a while it changes to brown whilst the top get shiny due to the wheels of the trains passing over it.
 

PaxVobiscum

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Also why do they allow overhead line supports to start going rusty? Isn't prevention the best strategy?

That sounds a bit more serious. I hope the OLE inspection teams are galvanised into action to deal with it.:D

I'll close the door after me.
 

Chris125

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Generally speaking rails are thick enough for rust not to be an issue, its the wear to the railhead and other defects that determine their lifespan.

Chris
 

Hydro

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Brand new rail and long unused rail is brown because the outer surface oxidises with the air. It's rust. All steel will do this, unless treated.
 

HSTEd

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I would imagine the steel used in rails would have similar properties to "Cor-ten" steels that are actually protected by the surface corrosion.
(These have alloying agents designed to make the rust stick to the steel to a far greater extent than normal, forming a passivating layer similiarily to aluminium)
 

brillopad

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Alphatek Hyperloy rails as installed at Dawlish seafront are different as they have a silvery anti corrosion coating - when they are welded as CWR the joins will go brown from rust and have to be re-coated manually.
 

PaulLothian

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As a follow-up question (sorry to spoil the fun)...

I have noticed that the colour of the rusting varies considerably - My favourite example is on the Kyle line at Garve, when the line alongside the road appears to glow orange. What are the variables?

Amount of traffic (and therefore dirt affecting the oxidisation process)?
Amount of moisture in the air?
Different alloys?

Serious replies welcome!
 

DownSouth

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As a follow-up question (sorry to spoil the fun)...

I have noticed that the colour of the rusting varies considerably - My favourite example is on the Kyle line at Garve, when the line alongside the road appears to glow orange. What are the variables?

Amount of traffic (and therefore dirt affecting the oxidisation process)?
Amount of moisture in the air?
Different alloys?
Could be all three.

If more traffic is causing more dirt/dust to coat the surface, that would at least make it appear different because a darker substance is present, a situation which would be the opposite in many areas of central Australia! Dirt/dust could also protect the surface and lower the rate of oxidation.

More moisture could increase the rate of oxidation, but how you get to the point of having more moisture present does matter.
If the moisture comes from more extreme temperature ranges over a daily cycle causing more dew to condense it won't make much difference. Lower temperatures slow down chemical reactions, and because pure water is a poor electrical conductor dew is not going to accelerate oxidation compared to normal rates.
If the moisture on the track is caused by mists or sprays of salty seawater on a line near the coast you'll get perfect conditions for oxidisation thanks to the electrical conductivity of salty water.

Differences in the chemical composition of the rail could be an issue in changing the appearance of a rail. Steel with more carbon might appear as a darker brown because it's a mixture of orange rust and black carbon particles.


With your example of observing the side of a rail on the Kyle Line, I would suspect it's simply that it's not disturbed much and that the low usage of the line lengthens the time between rails being replaced so a nice uniform layer has time to form. Lighting could make a difference in how you observe it as well, especially if there is dew on the rail when you see it as well.

The thing many people forget is that rust on the surface of a solid object like a rail or an OHLE pole is not a bad thing. It protects the rest of the metal underneath from corroding, and if it was scrubbed off you would merely start the whole process from scratch but with less of the pole/rail remaining than before.
 

pt_mad

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I noticed a few years ago that some of the masts on the way into Liverpool Lime Street were in a terrible rusty state. Havn't been up there for a while though so they may now have sorted it out?

Seems daft that they don't just re-paint the masts grey every few years? I noticed the new ones in Tamworth where the new four tracking starts havn't been painted at all. The old grey painted ones end and the new ones have been left bare steel which sounds like trouble.
 

PaxVobiscum

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I noticed a few years ago that some of the masts on the way into Liverpool Lime Street were in a terrible rusty state. Havn't been up there for a while though so they may now have sorted it out?

Seems daft that they don't just re-paint the masts grey every few years? I noticed the new ones in Tamworth where the new four tracking starts havn't been painted at all. The old grey painted ones end and the new ones have been left bare steel which sounds like trouble.

Corrosion of metals in an OLE environment is a very complex subject. We might need a physicist (or at least an Electrical Engineer) as well as a chemist. :)
 

1978NWUK

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I remember there was a big push on the WCRM a few years ago from Crewe going south painting the structures, I think more paint ended up on the insulators, reg arms and ballast than the actual structures, needless to say there's half painted structures all over the West Coast!!
 

paulb1973

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I remember there was a big push on the WCRM a few years ago from Crewe going south painting the structures, I think more paint ended up on the insulators, reg arms and ballast than the actual structures, needless to say there's half painted structures all over the West Coast!!

Presumably pollution as well as brake dust from trains and weathering etc is to blame. There are some very dirty looking OHLE structures in and around Bletchley and in the north London area on the WCML.
 

142094

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A lot of the older OHL stuff is copper, which is why it has the nice green tint to it due to the oxidisation. Probably worth a bit on the current market for scrap...
 

David

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A lot of the older OHL stuff is copper, which is why it has the nice green tint to it due to the oxidisation. Probably worth a bit on the current market for scrap...

Shh, or the pikeys will be out after the copper. Mind you, they will have a shocking time retrieving it all .....
 
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