FangShen-S5 well, containing CO_2 as high as 85%, is CO_2 Gas Well. The String in Downhole, pipeline and equipments on the ground of this Gas Well has been severely eroded, because of the high CO_2 content and water component. There are serious security risks. In order to solve the serious corrosion problem of pipeline and equipments of FangShen-S5 Well, it is an urgent need to studying on the corrosion mechanism of gas pipeline of CO_2 and equipments and some measures against the CO_2 corrosion mus...