Matters needing attention in the selection of standard gas packaging container materials

 In order to keep the content of the components in the standard gas and mixed gas basically unchanged for a long time, the selection of packaging container materials and the processing technology of the inner wall of the packaging container are extremely important.

High-pressure cylinders are one of the most commonly used packaging containers for mixed gas and standard calibration gas. Generally speaking, the main reasons for the change in the content of gas components in the cylinder are as follows: the chemical reaction between the gas components and the inner wall material of the cylinder; the adsorption of the gas components by the inner wall of the cylinder; the reaction between the gas components and the remaining water vapor in the cylinder or the Water dissolution and absorption; gas desorption of impurity components adsorbed on the inner wall of the cylinder, etc. For the above reasons, strict inner wall treatment of the cylinder must be carried out before the cylinder is filled with standard mixtures. Commonly used treatment methods include: polishing treatment of the inner wall of the cylinder; electroplating treatment of the inner wall of the cylinder (such as galvanized, nickel, chromium, copper, gold, etc.); phosphating treatment of the inner wall of the cylinder; chemical coating treatment of the inner wall of the cylinder, etc.

New methods for treating the inner wall of the steel cylinder are constantly being developed. For example, the Japanese patent reports that the inner wall of the steel cylinder is filled with oxygen or oxygen-containing gas after pickling and evacuating, so that a stable oxide coating is formed on the inner wall of the steel cylinder. The steel cylinder treated by this method is used to fill the standard standard calibration gas with low content, which can keep the standard calibration gas stable for a long time. Another example is Japan Oxygen Company, which has developed special treatment technologies for the inner wall of "T" and "TO", which are also suitable for filling low-content standard calibration gas. In recent years, special treatment technologies for the inner wall of gas cylinders have been researched and developed in China, such as coating the inner wall of the cylinder with an organic coating (such as fluororesin, etc.), which has the advantages of smooth inner surface, water repellency and corrosion resistance. In terms of the stability of the standard calibration gas, a new approach has been opened up.

In order to reduce the reaction and adsorption of gas components with the inner wall of the container, the selection of the cylinder material is also extremely important. The stability test of the standard calibration gas stored in steel cylinders of different materials (such as carbon steel, aluminum alloy and stainless steel, etc.) shows that it is better to use aluminum alloy steel cylinders to store the standard gas.