Scientists from the National Institute of Standards and Technology of the United States have developed a technique to detect corrosion in reinforced concrete at the early stages.

They assembled a laboratory installation with a terahertz waves with a power of about 2 milliwatts, on which they could detect hematite behind a concrete block with 25 mm thick. Researchers believe that a radiator with a capacity of hundreds of milliwatts it will be possible to detect corrosion products through 50 millimeters of concrete - as a rule, approximately on this thickness there is the first layer of reinforcement in reinforced concrete structures. In the future, scientists plan to find an absorption spectrum for acagenite, a product of corrosion of iron formed by exposure of salt water.

This is not the first attempt to use terahertz waves to study corrosion. In 2015, Japanese researchers used it to assess the deterioration of steel cables of suspension bridges through a protective isolating layer. The study is published in Applied Magnetic Resonance.