The Trying Estimatimation for Propagation Quantity of Crevice Corrosion by CCS Test for SUS304 Stainless Steel in Seawater Environment

Abstract

The propagation current density （i） of crevice corrosion depending on the external potential （E_out） is measured by the Continuous Current Step （CCS） method. The relate equation of E_out－i is obtained by CCS method. This current density should reflect the active corrosion rate in the metal chloride solution with low pH so called anolyte in crevice. According to this hypothesis, the propagation quantity of crevice corrosion （Q_{crev（CCS）}） will be electrochemically calculated by this relate equation of E_out－i.

The aim of this study is to compare the crevice corrosion quantity （Q_{crev（vol.）}） obtained by the corrosion volume of the specimen after the exposure test in natural sea water with Q_{crev（CCS）} calculated by the corrosion potential change during the exposure test.

The obtained results of this study were as follows：

The correlation between Q_{crev（vol.）} and Q_{crev（CCS）} was described as the following equation.

Q_{crev（vol）}＝8.8850＋0.2847･Q_{crev（CCS）}

It was confirmed that the crevice corrosion quantity during exposure test in natural sea water could be estimated from the time-dependent change of the corrosion potential in the exposure test by the relate equation of E_out－i obtained from the CCS method in the laboratory.