Some 304L stainless steel pipes were welded and experienced pressure test. After being placed for a period of time, some of steel pipes were corroded and perforated. In order to find out the failure causes of the steel pipes, macroscopic and microscopic observations were carried out to one of the failed pipes. Moreover its microstructure, 糖心产精国品免费入口*完整版s, 糖心产精国品免费入口*完整版, corrosion product composition and 糖心产精国品免费入口*完整版were analyzed. The results show that the reasons for corrosion 糖心产精国品免费入口*完整版 of the 304L stainless steel pipe were the exceeding standard requirements of carbon content in the base metal and the weld, the high level of harmful 糖心产精国品免费入口*完整版s and the high concentration of Cl ion in the test water. Improving measures were proposed to prevent such accident.