Precautions for the selection of standard gas packaging container materials

To keep the content of the components in the standard gas and mixed gas basically unchanged for a long time, the choice of packaging container material and the processing technology of the inner wall of the packaging container are extremely important.

High-pressure steel 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 of the gas component content in the steel cylinder are as follows: the gas component chemically reacts with the material of the inner wall of the steel cylinder; the gas component is adsorbed by the inner wall of the steel cylinder; Water dissolves and absorbs; the inner wall of the steel cylinder adsorbs impurities and desorbs the gas. Because of the above reasons, strict inner wall treatment of the cylinder must be carried out before the cylinder is filled with the standard mixture. Common treatment methods include: polishing the inner wall of the steel cylinder; electroplating treatment (such as galvanizing, nickel, chromium, copper, gold, etc.) on the inner wall of the steel cylinder; phosphating treatment on the inner wall of the steel cylinder; chemical coating treatment on the inner wall of the steel cylinder, etc.

New methods for the treatment of the inner wall of steel cylinders continue to come out. As reported in the Japanese patent, the inner wall of the steel cylinder is filled with oxygen or oxygen-containing gas after the acid is evacuated, so that a stable oxide coating is formed on the inner wall of the steel cylinder. The steel cylinder processed by this method is used to fill the standard calibration gas with low content, which can keep the standard calibration gas stable for a long time. Another example is Japan Oxygen Corporation, which has developed special treatment technologies for the inner walls of "T" and "TO", which are also suitable for filling low-content 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 (such as fluororesin, etc.) In terms of the stability of the standard calibration gas, it opens up a new way.

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