Failure Analysis of Corrosion Pit on Outer Wall of Membrane Wall Pipe

Abstract

Abstract Flue gas pipework is a critical component of a flue gas treatment system, mainly transporting the flue gases produced by a combustion plant from the source to the vent. Flue gas pipework is vital in all applications, such as thermal storage gas stoves, heaters, and gas water heaters. However, due to negligent management during the use of piping. Corrosion pits were created in several places on the outer wall of a membrane wall pipe located on the flue gas side of the membrane wall pipe. The external circulation medium of the membrane wall pipe is mainly high-temperature flue gas, and the internal circulation medium is water. This paper determines the causes of the corrosion pits by macroscopic observation, metallographic microstructure analysis, scanning electron microscopy, and energy dispersive spectroscopy (EDS). It was found that the outer wall of the flue gas sidewall pipe of the failed part was covered with reddish-brown rust, wide and shallow corrosion pits were observed, and the detection area of the inner surface of the pits had a high ‘S’ content. To reiterate, it was concluded that the cause of the corrosion pits was the flue gas dew-point corrosion.