Researchers at the University of Hong Kong (HKU) have announced a breakthrough in the development of stainless steel: the new "SS-H2" steel offers extremely high corrosion resistance and is therefore ideal for applications in the hydrogen sector.
Under the leadership of Professor Mingxin Huang, researchers at HKU's Faculty of Mechanical Engineering have developed the new "SS-H2" (stainless steel for hydrogen) steel with high corrosion resistance. This property predestines it for use in the extraction of hydrogen from seawater.
The discovery was published in the journal Materials Today under the title "A sequential dual-passivation strategy for designing stainless steel used above water oxidation". The research results have already been registered for patent in several countries. The first approvals have been granted.
Great potential for industrial application
Currently, expensive gold- or platinum-coated titanium components are required for water electrolysers in desalinated seawater or acidic solutions. With the new development of the SS-H2, electrolyser manufacturers can replace expensive structural components with more cost-effective steel. It is estimated that the cost of structural material can be reduced by a factor of 40 by using the new steel, which shows great potential for industrial applications.
Due to its superior corrosion resistance, SS-H2 represents a fundamental breakthrough compared to conventional stainless steel.
SS-H2 represents a fundamental breakthrough over conventional stainless steel due to this superior corrosion resistance. From the discovery of the stainless steel to the preparation of the official publication and hopefully industrial application, the team invested almost six years of work.
Double passivation leads to higher corrosion resistance
Stainless steel is an important material that is widely used in corrosive environments. An essential element for corrosion resistance is chromium. The oxidation of chromium forms a passive film that protects stainless steel in natural environments. However, as Professor Mingxin Huang's team has shown, relying on this passivation mechanism is a mistake.
The stainless super steel 254SMO has excellent resistance to pitting corrosion in seawater. However, transpassive corrosion limits its application. With conventional stainless steels, transpassive corrosion inevitably occurs at 1000 mV. This is below the potential of 1600 mV required for water oxidation.
The Chinese researchers have succeeded in preventing corrosion of their steel in chloride-containing media up to a potential of 1700 mV by means of "sequential double passivation". During double passivation, a secondary layer based on manganese is formed at 720 mV in addition to the passive layer based on chromium oxide.
