Effect of Environmental Factors for the Corrosion Behavior of Stainless Steels Exposed in River

Abstract

SUS304, SUS316 and SUS329J4L specimens with and without crevice are exposed in a river for up to 18 months with three conditions; in fresh water, brackish water areas and in the mud in order to investigate the relation between corrosion behavior and environmental factors of river, such as micro organisms and barnacles. Corrosion potential of the specimen was monitored continuously and specimens were collected successively to reveal the change of corrosion morphology including attachment of aquatic organisms. The results obtained are as follows. (1) Corrosion potential of all specimens immersed in fresh water or brackish water are ennobled up to about 500mV vs. SHE. (2) In brackish water, crevice corrosion occurred beneath barnacle on the specimens of SUS304 and SUS316. However, frequency of crevice corrosion to the number of barnacles attached is at most 3 to 4%. (3) The density of attached sulfate-reducing bacteria (SRB) increases under barnacle much more than on barnacle. (4) Corrosion of several forms occurs to specimens positioned in mud which reason may be due to SRB.