New findings on the stability of steel under the influence of hydrogen
Researchers at the Swiss Federal Laboratories for Materials Science and Technology (Empa) are investigating the mechanisms that lead to the hydrogen embrittlement of steel. Their findings will be used to build more stable bridges and to improve the infrastructure for storing and transporting green hydrogen.
Researchers from the Joining Technology and Corrosion Laboratory at the Swiss Federal Laboratories for Materials Science and Technology(Empa) are investigating the mechanisms that lead to the hydrogen embrittlement of steel. The team led by Chiara Menegus and Claudia Cancellieri is focussing in particular on the effect of hydrogen at the boundary layer between a passivation layer and the metal, according to a press release.
The passivation layer is an oxide layer around 5 nanometres thick that is formed during the oxidation of chromium contained in the steel. The passivation layer protects the steel from further corrosion. However, tests have shown that individual hydrogen atoms can react at the interface between the passivation layer and the metal and break down the protective oxide layer. This ultimately leads to embrittlement of the steel and can cause material fractures, as observed in buildings such as the Carola Bridge in Dresden, the London skyscraper 122 Leadenhall Street or parts of the Bay Bridge in San Francisco.
However, detecting the hydrogen atoms in the interface is complicated. “It is difficult to investigate a hidden interface inside the material without destroying the sample,” research leader Claudia Cancellieri is quoted as saying in the press release.
The researchers used hard X-ray photoelectron spectroscopy (HAXPES) for their investigations. This method showed that the hydrogen degraded the passivation layer.
In a further step, in collaboration with the Ion Beam Physics Lab at the Swiss Federal Institute of Technology in Zurich(ETH), various iron-chromium alloys are to be analysed and resistant oxide layers found. According to the press release, findings from this research could lead to the construction of more durable bridges and better infrastructure for the storage and transport of hydrogen.