Stainless steel for hydrogen applications
Stainless steel is vital for the low-carbon hydrogen economy
The anticipated fast growth in the hydrogen economy calls for stainless steel. Whereas some applications are technically established others are emerging and a sustained R&D effort is required to keep up with the materials challenges. At Outokumpu, our efforts are underpinned by close cooperation with universities and industrial partners to develop stainless steel solutions for the innovative hydrogen applications now emerging. Stainless steel offers the ideal combination of high strength, corrosion resistance and performance to make an important contribution to the climate change challenge as the world drives for Net Zero.
Stainless steels in the hydrogen economy
There is nothing new in using hydrogen as a fuel - it powered the very first internal combustion engines over two hundred years ago. And hydrogen fuel cells provided onboard electricity for the Apollo 11 moon landing in 1969. However, the development of a widespread hydrogen economy has seen a number of false dawns, both in the 1970s and at the turn of this century. Then, the main focus was on the transport sector. Now, thanks to the drive for Net Zero, we are seeing a broader understanding of how flexible, sustainable hydrogen can complement global energy distribution and storage, as well as a chemical, e.g. in reduction of iron ore. This will lead to it playing a significant role in boosting energy security, energy access and economic development while reducing air pollution.
Producing, processing, storing and using hydrogen presents significant challenges for materials in terms of the need for high strength to withstand high pressures as well as the capability to resist extremely low (cryogenic) and high temperatures. Stainless steels, especially austenitic grades, are ideally suited to meet these challenges.
Stainless steel for hydrogen storage
For many storage and transportation applications, hydrogen is liquified, requiring its temperature to be reduced to as low as -253°C. Austenitic stainless steel grades are ideal for use at cryogenic temperatures as they offer the combination of ductility and energy absorption essential for safety.
Another approach to storage and transportation is to compress gaseous hydrogen at high pressures, sometimes as high as 800 bar. This could result in hydrogen embrittlement in some materials, where the diffusion of the gas into the surface eventually results in cracking. Austenitic stainless steel is preferred generally as the hydrogen diffusion is much lower in austenite, compared to ferrite and martensite. Austenitic grades in our Supra range are often used, e.g. Supra 316L/4435.
Since many storage facilities will be in coastal areas with a salt-laden environment, the corrosion resistance of stainless steel becomes an important factor. The natural extension from storage is to filling stations, such as for refueling a fuel cell vehicle. The properties of stainless steel make it ideal for the manufacture of fuel dispensers, tubes and compressors.
Fuel cells and electrolyzers
A fuel cell converts hydrogen and oxygen into energy and water, while an electrolyzer uses energy and water to create hydrogen and oxygen. Stainless steel can be used in many different components such as interconnectors, the substrate for bipolar plates, anode- and cathode- plates, endplates, frames and connecting parts. The grade selected will depend on the operating temperature and environmental conditions. The strength and corrosion resistance of stainless steel enables the dimensions, and especially thickness of components, to be optimized for size and weight.
Bipolar plates are very demanding on materials. They must combine gas impermeability and tightness, good electrical and thermal conductivity and a high level of physical strength. Stainless steel has emerged as a very strong contender for cost-effective mass production. Outokumpu’s own investigations indicate that austenitic grades, such as Supra 316L/4404, are the current state-of-the-art as they offer the ideal combination of electrical conductivity, high corrosion resistance, excellent formability and high strength.
Read more about our stainless steels for bipolar plates: "Stainless steel stacks up for fuel cell bipolar plates".
Electrolysis needs clean water
The raw water used in the electrolysis process needs to be clean to ensure that the expensive catalyst lasts as long as possible. A number of different processes for water desalination and purification are used. Stainless steel is ideal for components used in water purification. The grade specified will depend on the water composition - mainly chloride content and temperature. The grades used are from our Supra to Ultra range. When the higher mechanical strength can be utilized, our Forta Duplex range is an excellent alternative.
Steam Methane Reforming
Steam Methane Reforming, SMR, is a mature process for producing hydrogen from fossil fuels. It is used generally for grey hydrogen, or for blue when carbon capture is applied. The process operates at 900°C. The materials used in the different parts of the process range from regular stainless grades to heat-resistant stainless steels as well as nickel base alloys.
Stainless steel is set to shine in the hydrogen economy
Whatever the colour of hydrogen involved, stainless steel offers the ideal combination of high strength, corrosion resistance and performance at both low and high temperatures to make an important contribution to the climate change challenge as the world drives for Net Zero. At Outokumpu, our efforts are underpinned by close cooperation with universities and industrial partners to develop stainless steel solutions for the innovative hydrogen applications now emerging. A typical example is our ongoing work on SOFCs where we are participating in several R&D and development projects.