The long-term storage possibility of the pure argon gas is based on chemical inertness and storage conditions. Argon is an element of group zero and hardly reacts with other materials under normal conditions (25°C, 1atm), whereas experimental findings show a purity decay rate of only 0.0003% per year (ISO 19227 norm). In storage of the cold-rolled seamless steel cylinder (material 34CrMo4, wall thickness 6.3mm), working pressure 13.5MPa, the argon leak rate can be maintained below 0.005%/year. For example, NASA stores pure argon gas in a K-type Dewar tank (volume 450L, vacuum layer thickness 50mm), and it is still 99.995% pure after 40 years, which meets the spacecraft welding protection demands.
The choice of storage container directly affects economy and safety. The annual evaporation rate of liquid argon storage tank (volume 10,000L, thermal conductivity of thermal insulation layer ≤0.02W/m·K) is about 0.08%-0.15%, and the pressure range of fluctuation of high-pressure gas cylinders (DOT-3AA specifications) is ±7% in the environment of -40°C to 60°C. In 2021, due to the use of non-standard storage tanks (vacuum degree only 10⁻²Pa) by a semiconductor company, the evaporation rate of liquid argon rose to 0.35%, and the annual loss was worth $120,000. ASME code requires liquid argon tanks to be equipped with dual safety valves (1.25 times operating pressure) that reduce the burst risk to 10⁻⁷ times/year.
Ambient temperature and humidity significantly influence storage life. The study shows that if the storage temperature exceeds 35°C, the oxidation rate of the inner wall of the cylinder is increased by 300%, and the concentration of oxygen impurity in argon is raised by 0.1ppm/year. Relative humidity above 60%RH will accelerate the aging of the valve seal ring, and the risk of leakage will increase from 0.01% to 0.7%. In 2023, a factory for medical equipment because of uncontrolled warehouse humidity (maximum 85%RH), which caused a pure argon gas storage tank O-ring failure, with a leakage loss of 8.5 cubic meters in 6 months, valued at $17,000.
Regulatory certification systems mandate storage conditions. Eu ADR 2023 stipulates argon cylinders for transport to undergo 5-year water pressure testing (test pressure 22.5MPa), and the wall thickness reduces by over 0.2mm, which is forced to scrap. China’s standard TSG 23-2021 requires liquid argon storage tanks to be equipped with a real-time monitoring system (pressure precision ±0.1MPa, temperature ±0.5°C). A chemical company was fined 380,000 yuan for failing to reach the standard, which made the purity of stored gas drop to 99.98%, resulting in production line halt and a loss of 2.4 million yuan.
Economically speaking, long-term storage should compromise risk and cost. Storage of liquid argon (-186°C) requires US $0.12 / m3 · year energy, while the requirement is US $0.03 / m3 · year for storage in high-pressure cylinders, but 75% of the floor space will be saved by the former. Germany’s Linde Group has calculated that for businesses with more than 500,000 cubic meters yearly usage, the return on investment period for the construction of liquid argon storage tanks (investment of $1.8 million) is 5.2 years, 19% less than the total cost of gas cylinder leasing.
Technological innovation is breaking the limits of traditional storage. Graphene-reinforced composite cylinders, such as Hexagon Purus’s Type IV cylinder, reduce wall thickness by 40% as bursting pressure increases up to 55MPa, allowing pure argon gas storage densities to increase to 300kg/m³ (compared to 160kg/m³ for conventional cylinders). Intelligent monitoring systems, such as Air Products’ SmartGuard, which used AI to predict the risk of leaks, resulted in 67% reduction in hardware failure and $83,000 reduction in annual support costs in one steel plant. NASA’s Deep Space Exploration program validated that in the hostile lunar environment (-170°C to 127°C), argon can be stored for 50 years in multi-layer insulated tanks with no more than 0.001% loss of purity.