Failure analysis of the 304 stainless steel tube in a gas analyzer

In this paper, the failure cause of the 304 stainless steel tube in a gas analyzer was investigated. It is found that the failure of the stainless steel tube is mainly attributed to local corrosion. Corrosive elements (chlorine, oxygen, and sulfur) were detected in corrosion products and fracture surface by energy-dispersive X-ray (EDX) analyzer. Further investigation revealed that a lot of tree-like cracks were observed on the surface of the tube, in which many cracks had already penetrated the whole tube wall, and transgranular propagated cracks were identified by field emission scanning electron microscopy (FESEM) and Optically Metallurgical Microscope (OMM). Besides, both the temperature and humidity were higher in the working environment of the stainless steel tube. As all we know, the type 304 stainless steel is very susceptive to chlorine ion (Cl−). Given all that, one conclusion was drawn that the failure cause of the stainless steel tube was attributed to stress corrosion cracking (SCC) caused by Cl−.