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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?

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    $\begingroup$ 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. $\endgroup$
    – Jedediah
    Commented Oct 31, 2023 at 2:43
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    $\begingroup$ I could name a few. Real estate, nuclear plants, pension funds. $\endgroup$
    – Guran
    Commented Oct 31, 2023 at 8:42
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    $\begingroup$ @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. $\endgroup$
    – JBH
    Commented Oct 31, 2023 at 15:12
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    $\begingroup$ @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. $\endgroup$
    – Richard Kirk
    Commented Oct 31, 2023 at 17:24
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    $\begingroup$ @user71659 High rolling friction. Poor efficiency. That's why trains still exist. $\endgroup$
    – DKNguyen
    Commented Oct 31, 2023 at 19:35

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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.

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    $\begingroup$ 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. $\endgroup$
    – Tonny
    Commented Oct 31, 2023 at 9:54
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    $\begingroup$ 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 (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. $\endgroup$
    – Mookuh
    Commented Oct 31, 2023 at 10:23
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    $\begingroup$ @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. $\endgroup$
    – Monty Wild ♦
    Commented Oct 31, 2023 at 12:59
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    $\begingroup$ "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. $\endgroup$
    – MikeB
    Commented Oct 31, 2023 at 12:59
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    $\begingroup$ 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. $\endgroup$
    – Nathan
    Commented Oct 31, 2023 at 13:06
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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.

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  • $\begingroup$ 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. $\endgroup$
    – The_spider
    Commented Oct 31, 2023 at 19:27
  • $\begingroup$ 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. $\endgroup$
    – supercat
    Commented Oct 31, 2023 at 19:40
  • $\begingroup$ @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. $\endgroup$
    – DKNguyen
    Commented Oct 31, 2023 at 19:51
  • $\begingroup$ @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. $\endgroup$
    – supercat
    Commented Oct 31, 2023 at 20:16
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    $\begingroup$ @supercat Doesn't sound like it would work then, which is why I guess things are coated in zinc. $\endgroup$
    – DKNguyen
    Commented Oct 31, 2023 at 20:28
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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?

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  • $\begingroup$ Or, stainless steel + galvanic anode, stopping the rust in the first layer? $\endgroup$
    – Erkin Alp Güney
    Commented Nov 3, 2023 at 21:20
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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.

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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.

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  • $\begingroup$ What do you think of my suggestion in another post of having trains occasionally dispense a zinc ribbon? $\endgroup$
    – supercat
    Commented Nov 1, 2023 at 20:37
  • $\begingroup$ @supercat It seems a bit complex as a solution, but it might work. $\endgroup$
    – Makyen
    Commented Nov 2, 2023 at 3:28

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