904 Gong, Gao, Meng, and Yang Materials and Corrosion 2009. 60. No. 11 (f) SEt wo Figure 8. SEM of pitting morphologies: (a)narrow and deep, (b)elliptical, (c) wide and shallow, (d) subsurface, (e) undercutting, (horizontal corrosion. According to Suresh Kumar et al. [9], a chloride ions concentration of not less than 10 ppm is sufficient enough to cause SCC at temperatures above 60C. Why only pitting rather than SCC was investigated at the inlet region of the steam pipes under the environment with high chloride ions concer temperature above 100C still needs to be explained. It is well known that SCC is caused by the combined effects of three factors: tensile stress, susceptible materials, and aggressive ions of which tensile stress is the major factor causing SCC. That the rotary steam pipes of the TA dryer are only under the compressive stress vertical to the pipes rather than the tensile stress along the pipes in service may account for why SCC did not occur in this case. Furthermore, the compressive stress was merely Figure g SEM of the delamination morphology of corrosion deposits 0.05 kg cm-g(about 5 kPa). So, only pitting occurred on the surface of the steam pipes. o 2009 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim www.matcorr.comcorrosion. According to Suresh Kumar et al. [9], a chloride ions concentration of not less than 10 ppm is sufficient enough to cause SCC at temperatures above 60 8C. Why only pitting rather than SCC was investigated at the inlet region of the steam pipes under the environment with high chloride ions concentration at temperature above 100 8C still needs to be explained. It is well known that SCC is caused by the combined effects of three factors: tensile stress, susceptible materials, and aggressive ions, of which tensile stress is the major factor causing SCC. That the rotary steam pipes of the TA dryer are only under the compressive stress vertical to the pipes rather than the tensile stress along the pipes in service may account for why SCC did not occur in this case. Furthermore, the compressive stress was merely 0.05 kg cm2 g1 (about 5 kPa). So, only pitting occurred on the surface of the steam pipes. 904 Gong, Gao, Meng, and Yang Materials and Corrosion 2009, 60, No. 11 Figure 8. SEM of pitting morphologies; (a) narrow and deep, (b) elliptical, (c) wide and shallow, (d) subsurface, (e) undercutting, (f) horizontal Figure 9. SEM of the delamination morphology of corrosion deposits within pit
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