Long-Term Dynamical Observation of Crevice Corrosion Propagation for SUS304 Stainless Steel in Natural Seawater.

It is very important to clarify the initiation and propagation behavior of crevice corrosion of stainless steel in natural seawater. Dynamic observation of the crevice corrosion behavior of SUS304 stainless steel with a metal/quartz glass crevice in natural seawater was carried out for 764 h. The corrosion potential of the specimen was continuously measured throughout the test duration. After the immersion test, the corrosion depth profile of the specimen was measured. The results were as follows. (1) The corrosion potential gradually increased up to about 600 mV vs. SHE by biofilm formation and dropped at 331.5 h immersion resulting from the initiation of crevice corrosion near the crevice mouth. (2) Crevice corrosion spread throughout the crevice as two-dimensional propagation, though the corrosion depth was very small. The propagation behavior of crevice corrosion after 100 h from the initiation of crevice corrosion changed from two-dimensional to threedimensional propagation, namely, toward thickness. (3) The average current through the immersion test was 74.5 µA calculated from the crevice corrosion volume measured after the immersion test. [ABSTRACT FROM AUTHOR]