Abstract: A 1Cr18Ni9Ti tee-part was found to have defects after pickling. In order to find out the failure cause, macro and micro observation, metallographic structure examination, composition analysis and acid washing experiment were carried out. The results show that the content of element Cr and Ni was obviously lower at the defeat areas than that at other areas so that the corrosion resistance of the defeat areas was worse than other normal areas. Preferential corrosion happened at the defeat areas in corrosive media and thus defects were found after pickling. The Cr-Ni poor areas formed during the electroslag remlting process of steel bar because some matter without Cr and Ni was melted into the steel matrix. Pickling examination can effectively prevent defective parts from use.