A research team from the University of Hong Kong has developed a new type of stainless steel that is resistant to severe corrosion in seawater. This material, named SS-H₂, could serve as a more cost-effective alternative to titanium in electrolyzers used for green hydrogen production.
Professor Mingxin Huang from the HKU Department of Mechanical Engineering led this project. The work forms part of his long-term “Super Steel” program. Previously, the team had already developed steel with anti-COVID properties and ultra-high-strength alloys.
Conventional stainless steel relies on chromium for protection, but this defense breaks down under the high potentials required for water electrolysis. SS-H₂ forms an additional manganese-based layer, which becomes active around 720 mV. Together, these two layers can withstand potentials up to 1700 mV in chloride-containing environments.
In saltwater electrolyzers, the new steel demonstrated performance comparable to titanium components. Furthermore, the cost of structural materials could decrease by approximately 40 times. For a 10-megawatt PEM system, this translates to significant savings.
The discovery of manganese passivation was unexpected. Traditionally, manganese has been considered detrimental to corrosion resistance. “Initially, we didn’t believe it because the prevailing view is that Mn degrades the corrosion resistance of stainless steel,” noted Dr. Kaiping Yu, the study’s first author.
The research spanned nearly six years. Scientists have filed patent applications in several countries, with two already granted. The article has been published in the journal Materials Today.
The team is now transitioning to industrial-scale production. Tons of SS-H₂ wire have already been manufactured at a factory in mainland China. The remaining challenge is to create meshes and foams from it for actual electrolyzers.
How exactly does manganese help overcome the fundamental limitation of ordinary stainless steel?
Professor Huang emphasized that their approach focuses on stability at high potentials, opening new possibilities for alloys in electrochemical applications. Should the material successfully pass trials in commercial systems, it could significantly enhance the affordability of green hydrogen production from seawater.
