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Railway ballast, for which natural crushed stone aggregates have been generally used, is an essential track component for the distribution of train loads along the rails and sleepers to the roadbed. However, the use of natural crushed stone aggregate causes environmental destruction as well as dust production in train service. This paper evaluates the feasibility of using the basic oxygen furnace (BOF) steel slag as railway ballast material. A series of physical and chemical quality tests are performed to investigate the characteristics of the materials associated with the effect of aging period due to the remaining free CaO and MgO in the BOF steel slag. Three different aging periods (i.e., 0, 3, and 6 months) are used to compare with various standards and the properties of the crushed stone aggregates. It is demonstrated that the physical and chemical properties of the BOF steel slag with different aging periods satisfy all requirements of standards sufficiently. Especially, the BOF steel slag without aging (i.e., 0 month) provides the similar physical and chemical properties, when compared to the BOF steel slag with aging (i.e., 3 and 6 months). Thus, it is possible to apply the BOF steel slag regardless of aging periods to the railway ballast materials instead of natural crushed stone aggregates.

The effects of the centerline segregation of Cr carbides and nonmetallic inclusions (NMIs) on the pitting corrosion of an Fe-13Cr-0.3C stainless steel (SS) plate produced by a continuous casting (CC) process were examined and compared with the effects on a plate produced by a strip casting (SC) process. For the CC plate annealed at 820°C, Cr carbides and NMIs were segregated in the centerline region, whereas they were uniformly and finely distributed throughout the SC plate. The resistance to pitting corrosion of the CC plate was much lower than that of the SC plate due primarily to the centerline segregation of Cr carbides and/or NMIs irrespective of whether annealing took place at 820°C or 1050°C. A micro-droplet cell test on CC samples revealed that the most dangerous site for pitting corrosion is the manganese sulfide (MnS) inclusion, followed by the centerline segregation of the Cr carbide. The oxide-type NMIs were not significant as sites at which pitting corrosion was initiated.

During etching treatments of printed circuit board (PCB) with ammnioa solution, galvanic corrosion occurs between electrically connected gold and copper, and resulting in unexpected over-etching problems. Herein, we determine corrosion of galvanic coupled Cu to Au quantitatively in ammonia solutions, and evaluate factors influencing corrosion of galvanic coupled Cu to Au (i.e., area ratio of anode to cathode and stirring speed). The difference of the corrosion rate (Δi = icouple, (Cu-Au)–icorr, Cu) of Cu connected to Au (117 μA/cm2) and of single Cu (86 μA/cm2) infers the amount of over-etching of Cu resulting from galvanic corrosion in ammonia solution (Δi = 0.31 μA/cm2). As the stirring speed increases from 0 to 400 rpm, the corrosion rate of galvanic coupled Cu to Au increases from 36 to 191 μA/cm2. Furthermore, we confirm that an increase in the area ratio (Au/Cu) from 0.5 to 25 results in a higher rate of corrosion of Cu connected to Au. The corrosion rate of galvanic coupled Cu to Au is approximately 20 times higher when the area ratio of Au to Cu is 25 (1360 μA/cm2) than when the ratio is 0.5 (67 μA/cm2).

In this work, we quantitatively examined the effects of temperature and operation parameters such as anode (Cu) to cathode (Au) area ratio, stirring speed, and Cu ion concentration on the galvanic corrosion kinetics of Cu coupled to Au (i couple ( Cu -Au)) on print circuit board in organic solderability preservative (OSP) soft etching solution. With the increase of temperature, galvanic corrosion rate (i couple ( Cu -Au) was increased; however, the degree of galvanic corrosion rate (i couple ( Cu -Au) - i corr (Cu)) was decreased owing to the lower activation energy of Cu coupled to Au, than that of Cu alone. With the increase of area ratio (cathode/anode), stirring speed of the system, i couple ( Cu -Au) was increased by the increase of cathodic reaction kinetics. And i couple ( Cu -Au) was decreased by the increase of the Cu-ion concentration in the OSP soft etching solution.