Argon is an inert gas used in various applications, from TIG welding to specialized laboratory environments. When people ask if argon “goes bad,” they are usually concerned about its shelf life within a cylinder. The simple answer is that argon gas does not chemically expire or degrade over time. Because it is a non-reactive element, its chemical composition remains unchanged indefinitely. The real issue is the potential for the argon’s purity to be compromised by external contaminants.
Why Argon Does Not Chemically Degrade
Argon is classified as a noble gas, found in Group 18 of the periodic table. This designation is the reason for its extreme stability and lack of chemical reactivity under normal storage conditions. Each argon atom possesses a full outer electron shell, known as an octet, meaning it has eight valence electrons.
This stable configuration eliminates the need for the atom to gain, lose, or share electrons. Since chemical reactions occur when atoms attempt to achieve this stable configuration, argon has no motivation to form bonds. This inherent stability ensures the gas cannot decompose, oxidize, or react with the cylinder material.
Sources of Argon Purity Contamination
While argon’s chemical structure is permanent, its purity can be easily compromised, making it appear to “go bad” to the user. The most significant source of contamination is the ingress of atmospheric air, primarily oxygen and nitrogen. Air can enter the cylinder or the gas delivery system through faulty valves, loose connections, or improper handling during cylinder changes.
For high-purity applications, such as TIG welding or semiconductor manufacturing, even trace amounts of these contaminants severely impact the process. Oxygen, for example, causes oxidation of molten metals, leading to poor weld quality or defects. Moisture, or water vapor, is another common impurity that enters the system, especially if residual moisture was left inside the cylinder during filling.
Contamination can also occur within the gas delivery system itself. If a system is run completely empty and the valve is left open, the cylinder pressure drops below atmospheric pressure, allowing external air to be drawn inside. Using non-compatible or low-quality hoses and regulators can introduce hydrocarbons or allow the permeation of oxygen and moisture into the argon stream.
Maintaining Argon Quality in Storage
Preventing contamination relies on meticulous cylinder handling and system maintenance. Always keep the cylinder valve tightly closed when the argon is not in use. Ensure the valve protection cap is securely in place during transport or storage, as this creates a physical barrier against air and moisture ingress.
Store argon cylinders upright and secure them with chains or straps to a solid structure to prevent accidental damage. The storage area should be cool, dry, and well-ventilated, away from ignition sources or direct sunlight. High temperatures increase the pressure inside the cylinder, while excessive humidity can cause the valve protection cap to rust.
Regularly inspect all connections, including the regulator, hoses, and fittings, for signs of wear or leaks. Using high-quality equipment designed for high-purity gas service, such as stainless steel bellows pigtails, helps prevent permeation contamination. Finally, always maintain a small positive pressure in the cylinder, avoiding running it completely empty, to prevent the backflow of atmospheric air.