塩化物イオンを含む炭酸塩/重炭酸塩水溶液中における炭素鋼の環境強度劣化 Environment-Induced Degradation in Strength for Carbon Steel in Carbonate/Bicarbonate Solutions Containing Chloride Ions
Electrochemical behavior and environment-induced degradation in strength for a carbon steel, SM400B, have been investigated in 0.025M Na<sub>2</sub>CO<sub>3</sub>+0.075M NaHCO<sub>3</sub> solutions containing various concentrations of NaCl at 363K. A slow strain rate test (SSRT) was employed to evaluate the degradation in mechanical properties. It was found from polarization curves that there generated pitting corrosion beyond 0.01M NaCl. The SSRT was carried out applying a potential below the pitting potential to the specimen in the test solutions containing 0.5 and 0.01M NaCl. Under both solution conditions, an increase in the applied potential resulted in a reduction in maximum stress and fracture strain, as well as an increase in current density during SSRT. From observation of the surface of the fracture specimens, however, there was no crack on it. Based on assumption of homogeneous deformation and general dissolution until maximum load, true stress at the maximum load was calculated. It was revealed that the true stress was almost independent of the applied potential, although the maximum load decreased with increase in the applied potential. It means that the homogeneous dissolution is accelerated by applying the stress and/or the dynamic strain. It is concluded from the facts that the degradation in the mechanical properties results from a rapid reduction in the cross section due to homogeneous dissolution, instead of localized corrosion.
- 材料と環境 : zairyo-to-kankyo
材料と環境 : zairyo-to-kankyo 47(12), 771-776, 1998-12-15
Japan Society of Corrosion Engineering