Corrosion Failure Reasons of Elbow Joint of an Oil and Gas Metering Device

The reasons for perforation of the elbow joint used in metering device of an oil production plant in crude oil medium was analyzed by observation of macroscopic morphology, microstructure, composition analysis of corrosion products and electrochemical method. The results show that the heat affected zone of the failed elbow joint had welding defects, which weakened the corrosion resistance of the joint.The main component of corrosion products was FeOOH, and oxygen corrosion was the main corrosion type. The outer arc side of the elbow joint had the weakest corrosion resistance, and was eroded by the fluid continously, which led to more serious corrosion and perforation in the end.