The University of Hong Kong
The new stainless steel for hydrogen
The material uses a dual protection mechanism that resists corrosion better than conventional stainless steel — and could replace the expensive titanium parts used in current hydrogen systems.
A team of scientists has developed a new “super steel” capable of withstanding diverse conditions to produce green hydrogen from seawater.
According to , this discovery could help build electrolysers that are resistant to seawater and economical enough for large-scale clean energy production.
Num, published in 2023 in Materials Todaythe team developed a special stainless steel for the hydrogen production (SS-H2). The material resists corrosion in conditions that typically push stainless steel beyond its limits, making it a candidate for producing hydrogen from seawater and other harsh electrolyzer environments.
Green hydrogen is produced using electricity, ideally from renewable sources, to break down water into hydrogen and oxygen.
It is known that the new technology could provide a more sustainable route to hydrogen, but corrosion, chlorine-related side reactions, catalyst degradation, precipitates and limited long-term durability remain major obstacles to its commercial use.
In a saltwater electrolyzer, the team found that the new steel performs comparable to that of carbon-based structural materials. titanium used in current industrial practice for the production of hydrogen from desalinated seawater or acid, the difference being in cost.
Titanium parts coated with precious metals such as gold or platinum are expensive, while stainless steel is much more economical.
According to the team, replacing these structural materials with SS-H2 could reduce the cost of structural materials. in about 40 times.
Stainless steel has been used for over a century in corrosive environments because it protects itself. The fundamental ingredient is chromium which, when oxidized, creates a thin passive film that protects the steel against damage.
In conventional stainless steel, the chromium-based protective layer can decompose under high electrical potentials. THE chromium oxide (Cr₂O₃) can be oxidized further, turning into hexavalent chromiumcausing corrosion.
Even the stainless steel 254 SMOa chromium-based reference alloy known for strong corrosion resistance in seawater, reaches this high stress limit. It may perform well in marine environments, but the electrochemical environment of hydrogen production is a different challenge.
The team’s response was a strategy called “double sequential passivation“.Instead of relying solely on the usual chromium oxide barrier, SS-H2 forms a second protective layer.
The latest research into seawater electrolysis continues to focus on corrosion-resistant materials, long-lasting electrodes, chlorine suppression, and system designs capable of withstanding real seawater rather than ideal laboratory solutions.
Still, the industry continues to search for materials capable of withstanding the combination of saltwater chemistry, high voltage and industrial operational demands. SS-H2 stands out because it addresses the problem not just with a coating or catalyst, but with a new alloy design strategy that changes the way stainless steel protects itself.
