The long term dynamical observation of crevice corrosion propagation for SUS304 stainless steel in natural seawater

摘要

It is very important to clarify the initiation and propagation behavior of crevice corrosion of stainless steel in natural seawater. Dynamical observation of crevice corrosion behavior of SUS304 stainless steel with the metal/ quartz glass crevice in natural seawater was carried out for 764h. 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 600mV vs. SHE by the bio-film formation and dropped at 331.5h immersion resulting from the initiation of crevice corrosion near the crevice mouth. (2) The crevice corrosion spread throughout the crevice as two-dimensional propagation, though the corrosion depth was very small. The propagation behavior of crevice corrosion after 100h from the initiation of crevice corrosion changed from two-dimensional propagation to three-dimensional one, namely toward thickness. (3) Average current through the immersion test was 74.5μA calculated from the crevice corrosion volume that was measured after the immersion test.