Building hydrogen storage infrastructure with proven stainless steel - made in America

In 2020, the Fuel Cell and Hydrogen Energy Association (FCHEA) worked with a coalition of major oil & gas, power, automotive, fuel cell, and hydrogen companies to develop a Road Map to a US Hydrogen Economy.  This comprehensive Road Map shows how critically important hydrogen is to achieve a lower-carbon energy mix, with the potential to generate $140 billion per year in revenue and 700,000 jobs by 2030, and $750 billion per year in revenue and 3.4 million jobs by 2050.

An important step in achieving this potential came at the end of 2023, with the announcement of a $7 billion investment by the Department of Energy (DOE) to create 7 hydrogen hubs across the country. The DOE has spread out the hubs both geographically and technologically. The aim of this diversified approach is to broaden the toolkit, including the support of blue hydrogen derived from methane with carbon capture. One of these hubs is the Gulf Coast – Texas, Louisiana, Mississippi, Alabama and Florida, a region that Outokumpu is well placed to support through our Calvert mill.

Our Calvert site in Alabama is America’s most technically advanced stainless steel mill with a complete melt and pour capability that enables our US customers to avoid the added cost and complication of import tariffs. All the key processes: melting, casting, rolling, annealing and pickling, and finishing, are performed in a fully integrated mill. Customized state-of-the-art finishing lines offer polishing, slitting and cut to length.

One of the main reasons why tank fabricators and original equipment manufacturers (OEMs) select Outokumpu’s stainless steel is that we offer a full scope of product forms including coils, strip, sheet and plate. We are also the only US producer of 72-inch product. This exceptional width can increase productivity by reducing the number of welds required to fabricate the complete tank.

It can sometimes be a complex task to identify the most appropriate material that will deliver reliability, long life and minimized total cost of ownership (TCO) for hydrogen storage. This is where our Alabama operation offers an important difference, because our team can call on a wealth of practical experience and technical knowhow combined with a wide, and developing, portfolio of grades. Their aim is always to provide the right grade, at the right time, from the right location.

Why choose stainless steel instead of carbon steel for hydrogen storage tanks?

As the hydrogen economy grows then safe and efficient production will require the construction of large numbers of storage tanks. Stainless steel is the optimal material choice because of its inherent corrosion resistance, while carbon steel will require the application of a protective coating that will need regular maintenance over the life of the tank.

In our experience, when you consider the excellent corrosion resistance, high strength, durability, low maintenance requirements and sustainability of stainless steel then over a 25-year typical life of a storage tank it is the option that delivers the lowest TCO. And at the end of life, it is fully recyclable.

Don’t fear the change

When we talk to engineering, procurement and construction (EPC) contractors, tank manufacturers and fabricators often express initial concerns that stainless steel is hard to work with. In fact, it is just as easy to use as carbon steel when it comes to forming, fabricating and welding. There are some tweaks to parameters that need to be made when substituting stainless for carbon steel. But there is nothing that requires a change of equipment. Whatever current equipment a fabricator has for stamping, bending and welding, they can use with stainless steel. The typical adjustments needed would be to pressures and welding heat and speed.

To help in making the change, Outokumpu’s team of technical advisors are always on hand to provide practical advice.

Furthermore, when specifying stainless steel, the benefits of partnering with a global supplier are crucial for many customers. One EPC contractor we work with said,

"We value that Outokumpu treats us like a global customer. So, we get the benefits of local US production, as well as access to global offers, and support from technical advisors on hand in the US and worldwide. That gives us the confidence to specify stainless steel from Houston for any project, anywhere in the world".

Stainless steel for hydrogen storage - the technical details

We asked Enrique “Henry” Zaldivar, Outokumpu Technical Solutions Manager for the US, to address two key technical concerns that customers can have when specifying materials for hydrogen storage – ductility at very low temperatures and hydrogen embrittlement.

Ductility at very low temperatures

In some cases, tanks will need to store liquid hydrogen at temperatures lower than 
-423°F/253°C. That calls for special materials with the ductility at low temperatures essential to avoid brittle fractures that could impact the structural integrity of a storage vessel.

The good news is that multiple grades of stainless steel are already well proven for this type of environment and are listed in technical standards such as the ASME Boiler and Pressure Vessel Code and EN 13445-2. Their common feature is a stable austenitic microstructure that gives them the toughness to operate at temperatures as low as -273°C.

In addition to handling the low temperature, the corrosion resistance of stainless steel is another important factor as hydrogen storage facilities are likely to be in coastal areas with a salt-laden environment. This will apply especially for projects on the Gulf Coast.

What about hydrogen embrittlement?

When storing hydrogen gas under pressure the potential risk of hydrogen embrittlement (HE) becomes another important factor when selecting the tank material. HE describes the reduction in the ductility of a metal due to absorbed hydrogen. Because hydrogen atoms are small, they can permeate solid metals. Once absorbed, the hydrogen atoms lower the stress required for cracks in the metal to initiate and propagate, resulting in embrittlement.

Different materials have varying sensitivity to HE. High-strength carbon steel, and titanium alloys are all vulnerable. Sensitivity also varies between different types of stainless steel.

Since the risk of HE increases with the pressure, there is little risk at low pressures, therefore most stainless steels are suitable for storing or transporting hydrogen at pressures usually below 20 bar. It is more difficult for hydrogen to diffuse into austenitic stainless steel than other stainless steel types such as ferritic and martensitic. That is why, along with its low-temperature ductility, austenitic stainless steel, such as 304L or 316L, is selected for many hydrogen storage applications that operate in the range of 200 to 300 bar. A typical application would be when storing green hydrogen for later re-feed as energy to the grid or for later use in process industry such as to produce fossil-free steel, as well as for liquid hydrogen storage.

A proven portfolio of stainless steel grades melted and poured in the United States

Our Alabama site has developed a wealth of experience in supplying stainless steel to the US tank industry. One austenitic grade we manufacture that is of particular interest for this application is Core 304L/4307, a low-carbon alternative to Core 304. The lower carbon content minimizes carbide precipitation following heat input, for example during welding, giving improved resistance against intergranular corrosion. This is a preferential or localized corrosion that proceeds along the grain/crystal boundaries or immediately adjacent to them. Although the majority of the metal is unaffected, and there is minimal loss of material, intergranular corrosion can cause catastrophic failure.

Core 304L is suitable for a wide variety of applications that require good formability and weldability and can be delivered with a variety of surface finishes.

Another important grade produced by our Calvert mill, is Supra 316L. This is generally considered to be the starting point for storage tanks in more corrosive environments. It is a low-carbon alternative to Supra 316. In the same way as the L version of Core 304, the lower carbon content minimizes carbide precipitation because of heat input, for example during welding, giving improved resistance against intergranular corrosion. Supra 316L is suitable for a wide variety of applications that require good formability and weldability and can be delivered with a variety of surface finishes.

Outokumpu is your partner for the US hydrogen economy

As the US hydrogen economy gears up for massive expansion, especially in the Gulf Coast, Outokumpu is ready to be your hydrogen partner. Our Calvert, Alabama  operation is well positioned and ready to support the construction of hydrogen storage tanks with austenitic stainless steel melted and poured in the United States, and backed up by a team with unrivalled technical knowledge and practical knowhow.