Measurements of Critical Pitting Temperature and Pitting Potential for Stainless Steels by using Crevice Corrosion Preventing Electrode

摘要

A newly designed working electrode on which occurrence of crevice corrosion is prevented with the flushed port cell has been developed in order to measure the critical pitting temperature, CPT, and pitting potential, E_(pit), for stainless steels.In the solution temperature range from 25 deg C to 100 deg C, the difference between the electrode surface temperature and bulk solution temperature could he maintained within 0.3 deg C in measuring CPT by using a pre-heating flushed water system. The measured values of CPT as well as E_(pit) which were obtained from 12 trials of the measurement under the same condition, were found to obey the normal distribution. E_(pit) at the constant temperature equivalent to CPT was found not to coincide with the setting potential for CPT due to the film formation in the CPT measurement. The mean value and deviation of E_(pit) obtained by using the crevice corrosion preventing electrode were almost equal to those of E_(pit), measured in the JIS method (JIS G 0577-1981). The newly developed method would be successfully applied to evaluate the difference in pitting corrosion resistance arising from the difference of surface finishing such as 2 D, 2 B, and BA, and the surface treatment of stainless steel.