Y Gong et al/Engineering Failure Analysis 31 (2013)203-210 (b) Fig. 2. External appearances of the "Yin-Yangcorrosion morphology on failed tubes. (a)Only on 4-in. tubes, (b) boundary line between "Yin'and'Yang' faces, (c)corrosion pits. Yin’face Yang'face R L20μm Fig 3. Microscopic morphologies of the failed tube cross-section:(a)total, (b)"Yin' face,(c)'Yangface 23 Matrix materials examination hemical compositions of the failed tube matrix material were listed in Table 1, which met the requirements of 316L pecification [ 10, the ultra-low carbon stainless steel with superior corrosion resistance only except to localized corrosions [1l2.3. Matrix materials examination Chemical compositions of the failed tube matrix material were listed in Table 1, which met the requirements of 316L specification [10], the ultra-low carbon stainless steel with superior corrosion resistance only except to localized corrosions [11]. Fig. 2. External appearances of the ‘Yin-Yang’ corrosion morphology on failed tubes. (a) Only on 4-in. tubes, (b) boundary line between ‘Yin’ and ‘Yang’ faces, (c) corrosion pits. Fig. 3. Microscopic morphologies of the failed tube cross-section: (a) total, (b) ‘Yin’ face, (c) ‘Yang’ face. Y. Gong et al. / Engineering Failure Analysis 31 (2013) 203–210 205