| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 91 === The research is discussing the natural corrosiveness, sea water corrosiveness, then analyzing with SD28 rebar and S20C carbon steel; also to compare when expose the material in the sea water and in the air, which contains sea water, and compare changes of mechanical character after stress corroded at different times.
Firstly, we discuss testing pieces weight variation after S20C carbon steel and SD28 rebar corroded in sea water; to get to know the changes of their most loaded and extension rate by pulling test. Secondly, we use scanning electron microscope (M-SEM) to know quantity changes of atoms on the surface and to see the corrosive situation on the material surface by eyes at different times.
The results show that: carbon steel and rebar do not have significant weights variance in air, but compare to carbon steel, rebar has less corrode weight reduction in sea water (after one year experiment, weight of rebar reduced about 4 grams and the carbon steel reduced about 25 grams). Furthermore, the observed surface corrode of carbon steel is serious than rebar, and it shows that rebar is more anti-corrode than carbon steel. The main reason for this condition is that the rebar material contains nickel, copper and chromium elements that carbon steel does not have. Besides, the longer the rebar and carbon steel soaked in sea water, the percentage of iron atom will higher than oxygen atom. In the experimental environment, prestressed specimen has higher tensile strength than the specimen without prestressed in sea water and air, and it revealed that more dislocation resulted from pre-stretch strain is due to time-effect function increase the tensile strength.
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