Gas commonly used in China is divided into four types: natural gas, liquefied gas, artificial gas and liquefied gas mixed with air, of which the smallest corrosive natural gas, followed by liquefied gas, the most corrosive artificial gas, artificial gas harmful Substances are mainly sulfur dioxide, naphthalene, coal tar and so on. Natural gas valve material can be no special requirements, if the use of ordinary carbon steel, must do the surface treatment to prevent corrosion. However, the valve in the artificial gas is best not to use ordinary copper material, it and sulfur dioxide into water after the copper sulfate, a great corrosion on the parts. To note is that artificial gas in the valve, the pipe is very easy to knot naphthalene, is a white crystal, it is hard, not easy to remove, affecting the valve to close and open. Coal tar sticking in the valve, the pipe is everywhere, very difficult to clean up. At present, there is no good solution. Artificial gas valve with low body pressure can use cast iron, medium pressure can use ductile iron, high pressure can be cast stainless steel (316). It is best not to use ordinary cast steel. Pneumatic control valve rubber diaphragm chamber shell is best not to use steel stamping structure, non-use, internal to do more advanced surface treatment (such as: nickel-phosphorus electroless plating, etc.).