The technological revolution of the inner lining of the IV-type hydrogen storage tank

With the rapid development of the hydrogen economy, safe and efficient hydrogen storage technologies have become a core challenge. Among them, the IV-type hydrogen storage bottle, due to its outstanding lightweighting level, has become the mainstream choice for on-board hydrogen storage. And in its core structure - the plastic inner liner - a material innovation is quietly leading a leap in safety and performance: the application of titanium foil as the barrier liner.

The " Achilles' heel" of IV-type hydrogen storage bottles and the necessity of the inner liner
The IV-type hydrogen storage bottle uses high molecular polymers (such as polyethylene) as the inner liner, and carbon fiber composite materials are wound on the outside to withstand high pressure (35 MPa or 70 MPa). Although this design achieves extreme lightweighting, it also brings two core challenges:

Hydrogen permeation: Hydrogen molecules are the smallest molecules and are highly capable of penetrating the inner walls of non-metallic polymers under high pressure, resulting in slow leakage of hydrogen and causing loss of gas storage capacity and safety risks.

Hydrogen embrittlement of carbon fiber composite materials: The released hydrogen gas will come into contact with the high-strength carbon fiber composite materials and accumulate at the interface, which may cause the fibers to separate from the resin matrix or degrade the performance of the carbon fibers themselves, thereby potentially leading to a decrease in the strength of the container.

Therefore, adding a very thin and dense metal barrier lining on the inner side of the plastic liner becomes the perfect solution to the aforementioned problem. And titanium foil is the outstanding choice in this solution.

Titanium Foil: The Superior Properties of an Ideal Barrier Liner
As the inner liner of an IV-type hydrogen storage tank, titanium foil demonstrates unparalleled comprehensive advantages: Extremely low hydrogen permeability: The titanium metal and its dense titanium oxide (TiO₂) passivation film on the surface form an almost impenetrable barrier, effectively blocking the penetration of hydrogen molecules or hydrogen atoms, and minimizing the hydrogen gas leakage rate.

Inherent resistance to hydrogen embrittlement: Unlike some high-strength steels, titanium alloys exhibit excellent resistance to hydrogen embrittlement. This means that the titanium foil lining can maintain its toughness and integrity even in a long-term high-pressure hydrogen environment without undergoing brittle fracture.

High strength-to-weight ratio and mechanical properties: Titanium foil offers excellent barrier properties while maintaining an extremely high strength-to-weight ratio. It can withstand the deformation and stress caused by the inner liner during blow molding and pressure cycling processes without tearing.

Excellent formability and adhesiveness: Titanium foil can achieve a strong interface bond with the polymer inner liner matrix through advanced composite processes (such as hot rolling), forming an integrated "titanium-plastic" composite structure, ensuring no delamination under complex loads.

Why is Titanium Grade 5 Sheet the pinnacle of performance?
Among various titanium materials, Titanium Grade 5 Sheet (Ti-6Al-4V) has raised the performance of the lining to a new level. As the most commonly used α-β titanium alloy in the world, it has obvious advantages compared to industrial pure titanium:
Ultra-high strength: Through alloying with aluminum (Al) and vanadium (V), the strength of Titanium Grade 5 foil exceeds that of pure titanium. At working pressures of 70 MPa or higher, it can achieve the same barrier effect with a thinner thickness, thereby enabling further lightweighting of hydrogen storage tanks, which is crucial for fuel cell vehicles that aim for ultimate range.

Outstanding fatigue strength: During vehicle operation, vibrations cause the hydrogen storage tank to undergo numerous pressure cycles. The excellent fatigue resistance of Titanium Grade 5 foil ensures that the lining can withstand alternating stresses throughout the entire design life of the container without developing microcracks.

Heat resistance improvement: During extreme conditions or during rapid hydrogen charging and discharging processes, the temperature inside the bottle may rise. Titanium Grade 5 foil has a better retention rate of high-temperature strength compared to pure titanium, providing a wider safety margin for the system.

Therefore, for the next-generation IV type hydrogen storage cylinders that aim for the highest safety standards, the longest service life, and the highest hydrogen storage efficiency, titanium Grade 5 foil has become the preferred material for the inner liner.

In the technological competition of hydrogen storage and transportation, material innovation is the key to determining the outcome. Titanium foil, especially the titanium Grade 5 foil with outstanding comprehensive performance, provides unparalleled safety guarantees for IV-type hydrogen storage tanks through its extremely low hydrogen permeability and inherent resistance to hydrogen embrittlement. It not only protects the carbon fiber shell from hydrogen erosion but also achieves ultimate lightweighting of the container through its excellent strength. With the maturity of the preparation process and the optimization of costs, the titanium foil lining technology will undoubtedly become the core pillar for high-pressure hydrogen storage containers to move towards higher pressures, greater safety, and greater economy in the future.

Fortu Tech supplies titanium foil products to multiple countries and regions around the world. Its service coverage includes the United States, Canada, Russia, Germany, France, the United Kingdom, Italy, Sweden, Austria, the Netherlands, Belgium, Switzerland, Spain, Czech Republic, Poland, Japan, South Korea, as well as Chile, Brazil, Argentina, Colombia and other places in Latin America.

Fortu Tech can produce and process Titanium Grade 5 pellet, Titanium Grade 5 foil, Titanium Grade 5 Capillary Tube, Titanium Grade 5 billet, Titanium Grade 5 sheet, Titanium Grade 5 plate, Titanium Grade 5 rod, Titanium Grade 5 tubes.