Hydrogen Pipe Materials: Why Stainless Steel is the Industry Standard
In a quest for cleaner energy solutions, hydrogen is fast becoming a key player in the transition to sustainable fuel sources. However, transporting hydrogen has been a major challenge all over the world due to its small molecular size, high diffusivity and potential for causing embrittlement in certain materials. This is where selecting the right hydrogen pipe materials comes in.
Choosing the wrong piping material while transporting Hydrogen may cause more harm than good. Hence, proper piping is very critical to ensuring safe and efficient hydrogen distribution across various industries. Although there are many available piping materials, stainless steel has become the industry standard for hydrogen piping, and we’ll see why in this article.
This article explores the key challenges of hydrogen transportation, the materials considered for hydrogen piping, and why stainless steel stands out as the most reliable option.
Material Selection for Hydrogen Piping
Selecting the right material for hydrogen pipe systems is crucial for ensuring safety, efficiency, and long-term durability. Below is a comparison of common materials used in hydrogen piping.
Carbon Steel
Carbon steel is widely used in conventional pipe systems due to its strength, cost-effectiveness, and ease of fabrication. Carbon steel may be strong, but it is highly susceptible to hydrogen embrittlement when exposed to hydrogen. Embrittlement is where hydrogen atoms infiltrate the metal structure, cause internal cracks and reduce mechanical integrity.
Additionally, carbon steel does not have adequate resistance to hydrogen permeation, meaning hydrogen molecules can slowly diffuse through the material, leading to leaks and reduced efficiency. In most industries, carbon steels usually have additional coatings or alloying elements, but their performance remains inferior to that of stainless steel.
Aluminium
Aluminium is suitable for many industrial applications because it is lightweight and corrosion-resistant. However, when it comes to hydrogen transportation, aluminium may not be the best option.
Aluminium has a relatively low tensile strength compared to steel and is not suitable for ASME hydrogen piping systems that require durability under high-pressure conditions. Another disadvantage of aluminium is degradation. Even though aluminium does not suffer from embrittlement like carbon steel, it is prone to hydrogen-induced degradation over time, especially when exposed to fluctuating temperatures and pressures.
Copper and Brass Alloys
Copper and its alloys, such as brass, are widely used in various piping systems because they have excellent corrosion resistance and ease of fabrication. However, as suitable as they may be for other piping systems, they are not very compatible with hydrogen infrastructure.
One major compatibility problem is that copper and brass have a high permeability to hydrogen, which means that hydrogen molecules will diffuse rapidly through them. This can lead to excessive energy loss and may pose safety risks in long-distance pipelines. Another limitation of copper in hydrogen piping is its relatively low mechanical strength. Copper cannot withstand the extreme pressures that come with hydrogen transport.
Stainless Steel
Over the years, stainless steel has become the industry standard for hydrogen piping due to its unmatched combination of strength, durability, and resistance to hydrogen-related degradation. For example, some grades of stainless steel, such as austenitic (e.g., 304L, 316L) and duplex stainless steel, have durability and corrosion resistance, making them ideal for hydrogen pipe systems.
The following are advantages and reasons why industries choose stainless steel for hydrogen piping over other materials.
Resistance to Hydrogen Embrittlement
Stainless steel is resistant to hydrogen embrittlement and can withstand extreme conditions. Unlike carbon steel, which is highly susceptible to embrittlement when exposed to hydrogen, stainless steel maintains its structural integrity, ensuring safe and long-lasting performance. This is particularly important for high-pressure hydrogen applications where material failure could lead to significant safety risks and operational inefficiencies.
Low Hydrogen Permeability
One of the key advantages of stainless steel in hydrogen piping is its low hydrogen permeability. Hydrogen molecules are very small and can easily diffuse through many materials, leading to leakage and energy loss. However, stainless steel, especially austenitic grades such as 304L and 316L can significantly contain hydrogen and reduce this risk.
High Strength and Pressure Tolerance
In addition to its permeability resistance, stainless steel is highly durable and can withstand extreme pressures, making it suitable for applications that require compliance with ASME hydrogen piping standards.
Corrosion and Temperature Resistance
Corrosion resistance is another critical factor that makes stainless steel the preferred choice for hydrogen pipelines. Exposure to hydrogen, particularly in environments with fluctuating temperatures and humidity levels, can lead to material degradation over time. However, stainless steel resists oxidation and corrosion, has a longer lifespan, and does not need frequent maintenance.
How Different Grades of Stainless Steel Perform Under Hydrogen Exposure
Stainless steel comes in various grades, and the most commonly used grades in hydrogen pipe systems are austenitic stainless steel (such as 304L and 316L) and duplex stainless steel.
Austenitic stainless steel
Austenitic stainless steel, especially 304L and 316 has very strong resistance to hydrogen-induced degradation. These grades contain high levels of nickel and chromium, which enhance their ductility and corrosion resistance. They can also resist cracking under hydrogen exposure because they do not have a phase transition at low temperatures.
Duplex stainless steel
This stainless steel has a balanced microstructure of austenite and ferrite and offers even greater strength and toughness than austenitic stainless steel. This makes it suitable for high-pressure hydrogen applications that require enhanced mechanical performance.
Martensitic and ferritic stainless steel
Unlike austenitic and duplex stainless steels, martensitic and ferritic stainless steels have lower toughness and are more susceptible to embrittlement. While they offer good mechanical properties in some applications, they do not provide the same level of hydrogen resistance as austenitic and duplex grades.
Conclusion
The combination of high strength, resistance to embrittlement, low permeability and corrosion resistance makes stainless steel the most effective material for hydrogen piping.
Now that it’s clear that stainless steel is the best for hydrogen pumping, the choice of stainless steel grade depends on the specific requirements of the hydrogen pipeline. It is important to consider pressure, environmental conditions, and long-term durability needs before choosing.