Relationship between preferential dissolution behavior and the holding potential and its duration of the potentiostatic test of a duplex stainless steel in simulated solution inside corroding crevice was investigated. In the active region (370, 300 and 260 mV vs. SCE), the current density decreased towards a certain value after the measurement started, then it stayed rather constant value until the end of the measurement, i.e., for 24 h. In the passive region (200 and 150 mV), it decreased greatly towards certain values after the measurement started, then it stayed lower value until the end of the measurement. In all potential regions, current density values determined by potentiostatic tests showed about one order of magnitude lower than those of the dynamic anodic polarization curves. At the less noble potential (370 mV) of the active region, ferritic phase preferentially dissolved, while that of noble (260 mV) of the active region, the austenitic phase dissolved preferentially. In the passive region, both phases dissolved evenly. These dissolution behavior were observed in the potentiostatic tests for 15 min as well as for 24 h. Chemical composition of dissolved metal ions after dissolution tests at certain potentials in the active region was also analyzed. Chemical composition of dissolved metal ions was almost same as chemical composition of a preferential dissolution phase of the specimen at each holding potential. It would appear that chemical composition of dissolved metal into crevice solution reflects to the preferential dissolution phase.

The purpose of this study is to clarify corrosion mechanism of a duplex stainless steel (DSS) through dissolution behavior of a ferritic phase and austenitic phase, respectively. A single phase specimen ([D] or [J] phase specimen) which has chemical composition of each phase of a DSS was prepared by preferential dissolution of the DSS, and dissolution behavior of each phase specimen was investigated. The [D] specimen showed a less-noble corrosion potential compared to the [J] specimen. The change of the corrosion potential of the DSS was located somewhere between those of each phase specimen. The [D] specimen showed a lessnoble active peak compared to the [J] specimen. The current density value of the DSS was located between the current values of each phase specimen. It was clearly shown that the corrosion mechanism of a DSS could be described through the dissolution behavior of single phases such as D phase and J phase.

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We examined characteristics of the propagation of conduction in width-controlled cardiomyocyte cell networks for understanding the contribution of the geometrical arrangement of cardiomyocytes for their local fluctuation distribution. We tracked a series of extracellular field potentials of linearly lined-up human embryonic stem (ES) cell-derived cardiomyocytes and mouse primary cardiomyocytes with 100 kHz sampling intervals of multi-electrodes signal acquisitions and an agarose microfabrication technology to localize the cardiomyocyte geometries in the lined-up cell networks with 100–300 μm wide agarose microstructures. Conduction time between two neighbor microelectrodes (300 μm) showed Gaussian distribution. However, the distributions maintained their form regardless of its propagation distances up to 1.5 mm, meaning propagation diffusion did not occur. In contrast, when Quinidine was applied, the propagation time distributions were increased as the faster firing regulation simulation predicted. The results indicate the “faster firing regulation” is not sufficient to explain the conservation of the propagation time distribution in cardiomyocyte networks but should be expanded with a kind of community effect of cell networks, such as the lower fluctuation regulation.

The objective of this study was to investigate and visualize the initiation and propagation of crevice corrosion in grade 2205 duplex stainless steel by means of time-lapse imaging. Transparent Poly-Methyl-Meth-Acrylate washer and disk were coupled with duplex stainless steel to create an artificial crevice, with electrochemical monitoring applied to obtain information about the nucleation and propagation characteristics. All nucleation sites and corroding areas inside crevices were recorded in situ using a digital microscope set-up. Localized corrosion initiated close to the edge of the washer, where the crevice gap was very tight, with active corrosion sites then propagating underneath the disk into areas with wider gaps, towards the crevice mouth. The growth was associated with a rise in anodic current interlaced with sudden current drops, with parallel hydrogen gas evolution also observed within the crevice. The current drops were associated with a sudden change in growth direction, and once corrosion reached the crevice mouth, the propagation continued circumferentially and in depth. This allowed different corrosion regions to develop, showing selective dissolution of austenite, a region with dissolution of both phases, followed by a region where only ferrite dissolved. The effect of applied electrochemical potential, combined with time-lapse imaging, provides a powerful tool for in situ corrosion studies.