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In How long would it take unused railroad rails to corrode below usability?, we are asked how long railway tracks would last, and in my answer, I show that while ordinary steel railway tracks are estimated to last up to 100 years before needing to be replaced, in practice they last around 30 years before being replaced due to corrosion.

However, that's for regular steel alloy rails. What if railway rails (and the other fittings such as the sleeper ties and clips that hold down the rails) were made from some variety of stainless steel? Would they last longer? Would they cost more? Would the extra cost be offset by a longer lifespan? If I'm envisioning a world where railway engineers have railways laid with stainless steel track and fittings, are they brilliant or barking?

In essence, this question is asking just one thing: What are the economic and engineering factors in the use of stainless steel rails that would make them more or less desirable than the current railway track alloys?

Monty Wild
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    I'm unaware of any [modern] businesses that have a 30+ year planning horizon, so the savings difference between an investment that requires an overhaul in 30 years or one that will last longer is unlikely to even be considered. – Jedediah Oct 31 '23 at 02:43
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    I could name a few. Real estate, nuclear plants, pension funds. – Guran Oct 31 '23 at 08:42
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    Which stainless steel? There are many types of stainless steel. Even if we assume the most common type, Austenitic, there are many grades. We can safely exclude 348, but which of the others do you think would best suit railroad rails? 316 for corrosion resistance? 314 for heat resistance? 303 for easy machining? – JBH Oct 31 '23 at 15:10
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    @Jedediah All railroads have a 30+ year planning horizon. Those that don't go bankrupt when surprised by a degrading rail system 30+ years into the future. Compare that to your common mom-and-pop retail store that might have a planning horizon of two weeks. – JBH Oct 31 '23 at 15:12
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    @Jedediah Much of the UK rail network was built in Victorian times when the bank rates were 1%. Many lines were build with repayment times of hundreds of years. There were exceptions: Brunel's Cornwall line GWR was built with wooden viaducts, which were replaced with stone after 25 years once the line had proved commercial. The wooden sleepers and ballast could be replaced by concrete, but iron has always been the choice for rails. – Richard Kirk Oct 31 '23 at 17:24
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    You can eliminate metal rails completely, just use concrete or asphalt which doesn't inherently corrode. It can't support as much pressure as steel, so you have to use a pneumatic tire. You now have a guided bus or people mover or rubber-tired tram. – user71659 Oct 31 '23 at 18:32
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    @user71659 High rolling friction. Poor efficiency. That's why trains still exist. – DKNguyen Oct 31 '23 at 19:35
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    The title of this question is one of many with the trivially obvious answer "No, because otherwise you'd see it in real life." The body is a much better question ("What factors would have to change before it would be worthwhile?") – thegreatemu Oct 31 '23 at 20:03
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    Just get some Rearden Metal – manassehkatz-Moving 2 Codidact Oct 31 '23 at 20:59
  • The 100 year lifetime has been misunderstood. That's 100 years for the system - bridges, cuttings, tunnels, earthworks, station buildings. Rails are consumable items in the system. – david Oct 31 '23 at 22:48
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    There are many examples of 19th century rails still in use on the UK railway network - not as running lines, but as fence posts etc. While there may be survivorship bias, it suggests that corrosion is not a primary issue here: track is usually well drained and not subject to the kind of corrosion where moisture becomes trapped. On sidings mid-20th century track can remain in usable condition - since they don't see a lot of traffic, they don't get much wear either. – user1908704 Nov 01 '23 at 10:37
  • Can you explain the difference in that Linked Answer, between '… heavy locomotives and rolling stock travelling at their full design speeds…' and '… and heavy use.…' which might mean some rails need to be replaced so much sooner? Since you're saying it 30/100 matters hugely, how are they not very-much the same? – Robbie Goodwin Nov 01 '23 at 13:39
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    @RobbieGoodwin some rolling stock might weigh hundreds of tons apiece. Rails used by such rolling stock can be worn and suffer from corrugations which need to be ground down. Corrosion can weaken the foot of the rail to the point where under full load, it might break, and if you run a few hundred kilogram handcar on corroded rails, even a rail that's corroded to the point that a regular train would derail, a handcar would still be safe. The 30/100 thing is that rail wear and rail corrosion are two separate factors. Apparently, worn rails can be reused in low-use sidings. – Monty Wild Nov 01 '23 at 21:29
  • I'm confident rust isn't an issue with current real world rails, or at least far below temperature stability (i.e. rails expand as they are heated and contract when cold). Too brittle a compound, the miles/kilometers of rail will break, not bend. It's not because of corrosion, it's because of the continuous expansion/ contraction. – CGCampbell Nov 02 '23 at 15:33
  • Thanks and while doubtless all that is true, how does it address the difference you cited between heavy locomotives and rolling stock travelling at their full design speeds…' and '… and heavy use.…'? – Robbie Goodwin Nov 03 '23 at 18:35
  • Sorry @Montywild, apparently the rule is now to close questions as story based when it is " about in world decisions of a character or organization" (ref : 1, 2). Unfortunately, being "desirable" depend on the choice of the buyers and seller's strategy. So I have to close even if I strongly disagree. If it gets closed and yet you aren't satisfied with the current answers, notify (@) me and I'll try to help you in chat. – Tortliena - inactive Dec 25 '23 at 21:29
  • @Tortliena This isn't story based at all, it's purely about expense vs utility, and I got a good answer, that SS is more expensive and not hard enough. Any organisation would agree with those results for a high-use line. In case you missed it, I haven't mentioned any organisation at all in my question. – Monty Wild Dec 26 '23 at 06:41
  • @MontyWild I agree (in the meaning I wish everyone agreed), but being "desirable" is actually bound by the decision made by the organization building it, ie. whether they want it or not. A project of this size is normally made through... Invitations to tender? Call for offers? Don't know the exact word. The choice of one or another bidder is... Well a decision made by the ones leading. And the final answer is dependent on the actual story circumstances at the time this decision is made. Please understand that's not the words I want to say :|. – Tortliena - inactive Dec 26 '23 at 08:32

5 Answers5

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Stainless steel is about four to five times more expensive than ordinary steel. This means that even in a perfect world where companies or States could plan for a time horizon of a century or more for the recovery of the investment, stainless steel rails would make sense only if the stainless steel railway could be depended on to last four or five times longer than an ordinary steel railway.

Which is not the case.

First of all, corrosion of the rails is not really a big issue. Running trains over the rails will naturally keep the rails rust-free. Rails will need replacing looooong before rust eats them away.

The real limiting factor of the life time of the rails is the deformation produced by the large forces exerted by the trains rolling on the rails. Part of the regular maintenance of the track is to periodically use a railgrinder to restore the shape and levelness of the rail heads; as a minor side effect, running the railgrinder over the rails will also get rid of any rust. But eventually the rail heads become so much out of shape that they cannot be safely be brought to spec to allow running fast heavy trains, and the rails are then taken out of the main lines and re-used in branch lines and side lines. Using stainless steel will not help with deformation at all, so that stainless steel rails will require replacement at least as often as ordinary steel rails.

Railways need expensive maintenance anyway. The rails themselves are not the main problem; everything else is. In particular, the ballast on which the sleepers sit will need to be tamped and clean-up periodically, at great expense. Screws need tightening. Switches need lubricating. The track must be inspected periodically to check that the rails remain level and parallel. And so on and so on.

AlexP
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    It might still be worthwhile in the long run, on a low-gravity planet with a lot of long distance trajectories with few bends (less deformation) and an atmosphere that really promotes rusting, to which stainless is more resistant than the regular steel. It all depends on your setting. On Earth it ain't worthwhile, but elsewhere it could be made to work. – Tonny Oct 31 '23 at 09:54
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    Stainless Steel being 5 times as expensive as regular steel does not mean the track will be 5 times as expensive, since the steel itself is only part of the total cost. Using this source (https://www.rail-track.com/how-much-is-rail-track/) and doing a very rough back-of-the-envelope calculation, the price of the track would roughly double if you include cost for labour and other materials. – Mookuh Oct 31 '23 at 10:23
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    @Mookuh It doesn't matter if stainless rails are 5% dearer than regular rails if they don't last any longer. If they lasted for 60 years, it'd be worth it for the lower delay and labour to replace them, but if the problem isn't corrosion, there's no point. – Monty Wild Oct 31 '23 at 12:59
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    "Running trains over the rails will naturally keep the rails rust-free." I'm not sure if you realise, but that is a bit mis-leading as I read it. The reality is that the rails still rust, but that running trains remove the rust before it is obvious; they don't prevent it. If anything, exposing fresh metal may speed up corrosion very slightly. – MikeB Oct 31 '23 at 12:59
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    @MikeB: Yes, but they also polish the surface, meaning that the area exposed to the elements is kept at a minimumum. – AlexP Oct 31 '23 at 13:01
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    Stainless steel has inferior abrasion resistance compared to carbon steel. I think it would be a worse material for this use case, even if it was cheaper. – Nathan Oct 31 '23 at 13:06
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    @MontyWild That is true and I'm not doubting the merit of the answer in general. I'm merely commenting on the fact that a 400% increase in steel prices does not equal a 400% increase in project cost. – Mookuh Oct 31 '23 at 16:28
  • Another thing about the cost: steel is cheap, so all those train tracks lying unattended stay there. If they were stainless, they'd be a lot more... locomotive (they'd "grow legs" / be stolen). – IronEagle Nov 01 '23 at 00:29
  • An alternative to stainless steel would be high-phosphorus steel. It weathers to develop a thin coating of rust, but then develops a phospated layer which prevents further rusting. I have no idea about whether its metallurgically suitable or about the economics. I would not expect small percentages of phosphorus to add serious expense as a raw material. – nigel222 Nov 01 '23 at 10:21
  • @nigel222: Copper (and alloys, such as bronze) is roughly ten times as expensive as steel. Steel is cheap, plentiful, and absolutely good enough for most applications. (And copper has limited availability, whereas even the most dedicated environmentalist will admit that there is no risk of ever running out of iron.) – AlexP Nov 01 '23 at 10:53
  • @nigel222 the intense friction would wear off the phosphated layer. – RonJohn Nov 01 '23 at 13:17
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    @RonJohn no more than it wears down the unprotected steel? It doesn't form a layer like phosphate paint. It accumulates in the steel itself. The process of forming rust drives phosphorus inwards from the steel which has rusted, making it progressively less rust-able. (Phosphate paint works the same but can't renew once the paint has gone). High traffic rails get worn out before they get rusted out. I'd assumed low enough usage that rust was the killer. – nigel222 Nov 01 '23 at 13:53
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Stainless steel is TERRIBLE for train tracks. Especially if you are trying to use the most rust resistant grades.

Expensive to produce

Difficult to fabricate

Stainless is difficult to machine compared to carbon steel. It wears tools faster and can't be machined as quickly. Some are considered a nightmare.

Difficult to weld, if you can even weld it at all

Less Hardenability

Stainless cannot be hardened as much as carbon steel and austentic grades (the most corrosion resistant grades) cannot be hardened at all. And the kinds that can be hardened (martenistic and ferritic) will rust when exposed to standing fresh water.

Constant Abrasion Reduces Corrosion Resistance

If you're constantly abrading the stainless steel then you are constantly breaking thee passivation layer preventing further corrosion, forcing it to reform. This is true of even the most corrosion resistant grades.

Galling

Stainless, especially austentic stainless (the most corrosion resistant class) is known for galling and when it does you are tearing chunks out of the material. Austentic grades are flat out not used for bearing surfaces because of this. Not good for something bearing enormous, moving loads like train tracks.

Some stainless grades are used for bearing surfaces, namely 4140. Found in ball bearings, but it rusts after long term exposure to fresh water.

Not as corrosion resistant as you might think The austentic grades of stainless steel (the most commonly encountered are 303 and 304) cannot stand up to salt water exposure These are what your typical eating utencils are. Your stainless appliances or laundry machine tub are probably 430 which is less rust resistant. It is not until you get to 316 where you can tolerate salt water exposure but the cost increase is significant and the machining can be a nightmare. 4140 is a common martenstic grade used for strength, hardenabiliy. It is commonly encountered in knives and campers will tell you that these rust. It just doesn't need to be babied like a carbon steel knife. Stainless steels have very clear tradeoffs between mechanical properties and corrosion resistance. Weldability is another distinctive trade-off too.

DKNguyen
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  • As long as you don't build the train tracks in an area that regularly floods, rusting when exposed to (standing) fresh/salt water isn't really a problem. – The_spider Oct 31 '23 at 19:27
  • What would be the practicality of having a groove in the rail into which a train would occasionally dispense zinc wire? It wouldn't matter if the wire was continuous; any water which was in contact with both the wire and the steel would be unable to corrode the steel. – supercat Oct 31 '23 at 19:40
  • @supercat If you want to go that route I imagine you could just do that at one far end of the track. Rather than go to the complication of sticking it onto a train and dispensing it. – DKNguyen Oct 31 '23 at 19:51
  • @DKNguyen: For zinc to protect part of the rail, there must paths between that part of the rail both through water and through metal. Putting a lump of zinc at one end might work if the entire rail was submersed, but it would do nothing to protect parts of the steel in parts of the steel that aren't connected through water. – supercat Oct 31 '23 at 20:16
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    @supercat Doesn't sound like it would work then, which is why I guess things are coated in zinc. – DKNguyen Oct 31 '23 at 20:28
  • @The_spider Salt water corrosion will be an issue near any body of salt water, as even without flooding, salt air (from sea spray) is shown to cause significant corrosion within 50 miles of the ocean, and one study detected sea spray in Boulder, CO (900 miles from the ocean). Additionally in areas with regular winter weather, where salt is used on roads to remove ice, that road salt will mix with the melted ice and any subsequent precipitation (plus spray from passing vehicles) to corrode any nearby metal. – RisingZan Nov 02 '23 at 15:51
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No, stainless is not rustfree.. stainless steel just rust one layer and then stops. But as the train grinds over it, the rust comes loose, making it just as rustable as the rest of the steels.

PS: Why not use normal steel + https://en.wikipedia.org/wiki/Galvanic_anode?

Pica
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It might be reasonable for a niche in the railway business.

Infrastructure is usually built with a pay back time of about 25 years. This means that the company using it will spend 25 years repaying the expenses occurred to build it, and any more year of usage is free juice.

Using stainless steel with the same payback time would result in higher usage fees, thus more expensive tickets. That might be OK for premium services, like high speed trains, not for more cost sensitive operations like logistics and cargo.

On the other hand going for longer payback time might increase the risk of the investment: it's not granted that a railway will stay operational for 30+ years.

You see something similar for airlines: last generation planes are used for transporting people on remunerative routes, while older models are used for cargo and peripheral routes.

L.Dutch
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Using stainless steel is unlikely to be the solution chosen

It's probably possible that you could envision a world where the engineering trade-offs made it reasonable to use stainless steel. However, that would likely require significantly tweaking the economics of the entire lifetime of the track, the atmospheric conditions to make corrosion substantially more of an issue than it is in our world, and some of the properties of stainless steel in order to make it more attractive for this use.

These would need to be fairly significant changes among all aspects of the lifetime of the rails. As has been discussed in other answers, using stainless steel for this application has serious negatives in our world. The changes would need to make the economics of using stainless steel sufficiently favorable in order to overcome all of those negatives. In addition, the changes would need to make alternate solutions to corrosion control not economically feasible.

Use other methods of corrosion control (e.g., cathodic protection)

An important aspect that hasn't been discussed in other answers is that there are other, more effective, methods of controlling corrosion, or even just designing for accepting more corrosion, which are already in use in the real world in environments where corrosion is more of an issue. In our world, such environments are typically where water, especially salt water, is present in significant quantities. Some examples of those environments include boats/ships, water heaters, underground structures, in-water structures, etc.

In such situations, the typical choice, in addition to other mitigations (e.g., painting or other coatings, which, obviously, aren't options for railway track, due to the nature of their use), is to use a form of cathodic protection, which is either impressed current cathodic protection (ICCP), where a voltage is constantly applied to prevent corrosion of the material being protected, or using a sacrificial anode, more properly called a galvanic anode to have the corrosion occur in another metal object that's electrically connected to the rails. Such sacrificial anodes can be made to be substantially easier monitor for excess corrosion and easier and less expensive to replace when needed.

Makyen
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