It is extremely important to keep the content of the components in the mixed gas and the standard calibration gas constant for a long period of time, the choice of the material of the packaging container and the processing technology of the inner wall of the packaging container.
High-pressure cylinders are one of the most commonly used packaging containers for mixed gas and standard calibration gas. Generally speaking, the content of gas components in the cylinder is changed mainly for the following reasons: the gas component reacts with the material of the inner wall of the cylinder; the gas component is adsorbed by the inner wall of the cylinder; the gas component reacts with the residual water vapor in the cylinder or is The water dissolves and absorbs; the inner wall of the cylinder adsorbs the desorption of the impurity component gas.
For the above reasons, strict cylinder inner wall treatment must be carried out before the cylinder is filled with the standard mixture. Commonly used treatment methods include: polishing the inner wall of the cylinder; plating treatment on the inner wall of the cylinder (such as galvanizing, nickel, chromium, copper, gold, etc.); phosphating of the inner wall of the cylinder; chemical coating treatment of the inner wall of the cylinder.
A new method for the treatment of the inner wall of steel cylinders has been continuously introduced. As reported by the Japanese patent, the inner wall of the cylinder is filled with oxygen or an oxygen-containing gas after pickling and evacuation, so that a stable oxidized coating film is formed on the inner wall of the cylinder. The cylinder treated by this method is used to fill a low standard of standard calibration gas, which can keep the standard calibration gas stable for a long time. Another example is the Japanese Oxygen Company's special treatment technology for the "T" and "TO" inner walls, which is also suitable for filling low-level standard calibration gases. In recent years, domestic research and development of special treatment technology for the inner wall of gas cylinders, such as the coating of organic coatings on the inner wall of steel cylinders (such as fluororesin, etc.), has the advantages of smooth inner surface, water repellency and corrosion resistance, etc. 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 vessel, the choice of cylinder material is also extremely important. Through the stability test of the standard calibration gas for cylinders of different materials (such as carbon steel, aluminum alloy and stainless steel), it is shown that
It is better to use the aluminum alloy cylinder storage standard calibration gas. At present, Shanghai, Qiqihar, Shenyang and Chongqing have produced aluminum alloy cylinders. The aluminum alloy gas cylinder called “SpectralSeal†has been successfully developed in China, which can maintain the long-term stability of the trace component content in the standard calibration gas.