Abstract
The localized corrosion of type 304 stainless steel was investigated using the a-c automatic corrosion monitor deviced recently in our laboratory, with special interest to detect the initiation of localized corrosion. The a-c corrosion monitor permits to record the time-course of the net corrosion rate of specimen. The corrosion rate of the stainless steel in NaCl solution was relatively low at initial periodes but, after certain incubation time, it increased rapidly by more than forty times indicating a pit propergation. It was also noticed that higher the corrosion rate during the incubation time, shorter the incubation time. A similar incubation time was also observed on crevice corrosion of the specimen with an artificial crevice. The rate of crevice corrosion of type 316 stainless steel was less than that of type 304 and 304-L, while the rates also depended on the ratio of anode/cathode area.
Since the net corrosion rates measured by the a-c corrosion monitor were well consistent with those estimated from the weight loss of the specimen, it is found that the corrosion monitor can be used to monitor not only general corrosion but also localized corrosion.
