If you have noticed those dark sleepers while taking a walk by the railway, you may find them unremarkable and even rough in appearance. But you may not know that behind these seemingly ordinary woods lies a set of industrial anti-corrosion processes that are rarely known to the public. Unlike many people's imagination of "brushing a layer of anti-corrosion paint", the anti-corrosion treatment of railway sleepers is actually a deep level treatment from the outside to the inside.
1、 Why choose pine wood?
One of the preferred woods for sleepers under railway tracks is pine wood. Pine wood is relatively soft and has smooth fibers, making it very suitable for a key treatment - oil immersion anti-corrosion. This characteristic is like a loose and porous sponge that can fully absorb anti-corrosion oil, rather than being dense and difficult to penetrate like some hardwood.
However, pine wood itself is not durable. If a fresh pine tree is directly laid under the railway tracks, it may rot and lose its support in less than a few years due to exposure to sunlight, rain, and microbial erosion. So, it must undergo a special anti-corrosion treatment.
2、 Brushing paint? That's just superficial effort
Many people associate it with anti-corrosion paint applied to furniture or doors and windows. This method is almost meaningless for sleepers.
Imagine coating a piece of bread with only a thin layer of jam, which looks shiny on the surface but still soft on the inside. Once the jam layer is damaged, moisture and mold will drive in. Sleepers face long-term invasion from ultraviolet radiation, rainwater, soil fungi, and insects and ants. Most surface coatings will crack after mechanical wear and thermal expansion and contraction, thereby losing their protective effect.
So, painting is far from enough for railway sleepers that require decades of service.
3、 Carbonization treatment? The cost is intensity
Some people have also heard of carbonized wood. Baking wood at high temperatures to form a carbonized layer on the surface, like putting a layer of armor on the wood, can indeed prevent insects and corrosion.
But the problem is that high temperatures can damage the overall structure of wood, reducing its strength and toughness. For sleepers that need to withstand repeated impacts from trains weighing tens of tons, losing strength is fatal. Carbonization treatment is more suitable for outdoor flooring and gardening landscapes, but it cannot withstand the constant crushing of trains day and night.
4、 The core of anti-corrosion treatment for sleepers: oil immersion treatment
The railway sleepers truly rely on a process called "oil immersion anti-corrosion".
The newly cut pine wood will be peeled, cut into standard sizes, and then put into a huge sealed jar. Under vacuum conditions, the anti-corrosion oil heated to a certain temperature will be injected into the tank. At this time, high pressure is applied for several hours, and the pressure difference between the inside and outside of the wood is huge. The anti-corrosion oil will be "forcibly injected" into the deep layers.
After this process, the pine wood underwent a complete transformation. It has a depth of at least 13 millimeters and is filled with anti-corrosion oil, becoming heavy, dark, and oily, as if possessing steel like corrosion resistance. The service life of such sleepers can be extended from a few years without treatment to over a decade or even several decades.
5、 Invisible project, silent guardian
Nowadays, although the application of concrete sleepers and steel sleepers is increasing, anti-corrosion wooden sleepers are still irreplaceable in specific routes and regions, especially in road sections that require certain elasticity, insulation or complex terrain.
These dark oil immersed sleepers carry the steel rails and stand silently in the ballast. They are not as eye-catching as speeding trains, but it is this "uncommon" deep anti-corrosion process that ensures the stability and safety of railway foundations for decades on an invisible level.
