Czech scientists study how salt destroys metal structures to protect bridges and spacecraft
Winter coats roads and bridges with salt, and when mixed with moisture, it slowly and relentlessly eats away at metal structures. Scientists at the Institute of Physics of Materials of the Academy of Sciences are trying to combat this. In their laboratories, they subject steel to extreme stress, monitor its failure, and develop new metal alloys designed to last longer, whether on bridges or in space.
Jan Klusák from the Institute of Physics of Materials of the Academy of Sciences shows an ultrasonic pulsator used for testing material fatigue. A steel sample is clamped in a metal box resembling an aquarium, where scientists repeatedly stretch and compress it until it breaks. Klusák explains the process to Czech Radio:
“We subject the sample to cyclic tension and compression. This means that we repeatedly stretch and compress it at a frequency of 20,000 Hz, that is, 20,000 times per second.”
They have several corroded samples that they are testing. By carefully monitoring individual samples, scientists can estimate how long the material will last, for example, in the case of a rusting bridge pier under normal operation.
“We have three sets of high-strength steels here. They are used in bridge or crane structures. And if we imagine bridges that cars drive over, the road surface is treated with salt so that they don’t slip in winter. Of course, this salt, in combination with moisture, greatly contributes to the corrosion and degradation of bridge structures.”
This is crucial for steel bridges, which are exposed to salt for long weeks during winter. Without salting, it is difficult to imagine safe driving in freezing conditions.
“Salt water has a lower freezing point, which is why salt is added. It prevents water from freezing on the road.”
Steel for space rockets
Scientists from the Academy of Sciences are also working on other anti-corrosion solutions. They move on to the testing facility, where metal samples are subjected to alternating loads. This steel is intended for space rocket hulls and launch pads. Zdeněk Chlup from the Institute of Physics of Materials with more:
“We had to develop this device as part of a project for the European Space Agency, in which we committed to developing a completely new material suitable for space rocket launch applications. These usually take off somewhere near the coast, where there is a salty environment.”
The scientists developed the tested steel themselves. It is a new stainless alloy with nanoparticles that increase strength, ductility, and corrosion resistance.
Then it is immersed in the solution for 10 minutes and then left in the air for 50 minutes. The scientists are currently in the material development phase. The next step will be scaling up production, followed by introducing the material to industry.
Chlup also detailed why metals are so susceptible to salt in the first place:
“Metals are composed of grains, which we can imagine as small crystals, and there are usually many defects between these grains. Salt water disrupts the bonds between the crystals and reduces the load-bearing cross-section of the material.”
The outcome of this work could result in more durable bridge structures and lighter spacecraft with reduced fuel consumption and, as a result, extended range.
