Hydrogen Absorption Behavior of Steel Bar for Prestressed Concrete in a Solution of Ammonium Thiocyanate

Method of Evaluating Delayed Fracture Susceptibility of Tempered Martensitic Steel Showing Quasi-Cleavage Fracture

“…The surface states probably continued to change during immersion since corrosion products cyclically form and peel off due to brittleness. [8] Thus, the unstable fracture strengths obtained with the immersion method are attributed to unstable surface states during the tensile tests, whereas the fracture strengths obtained with the cathodic electrolysis method were affected by only the hydrogen content as the surface state did not change. Accordingly, these findings reveal that the difference in hydrogen charging methods affected the results of the delayed fracture evaluation; the fracture strengths obtained with the immersion method were affected by the hydrogen content and surface state, while the fracture strengths obtained with the cathodic electrolysis method were affected only by the hydrogen content.…”

“…A metallic luster was observed on the specimen surfaces both (a) before hydrogen charging and (c) after cathodic electrolysis. In contrast, the specimen surface (b) after immersion lost its luster and was covered with a black corrosion product that was found by analysis to consist of Fe, O, and S. [8] Scanning electron micrographs of specimen surfaces at the notches (a) before hydrogen charging, (b) after immersion, and (c) after cathodic electrolysis are shown in Figure 5.…”

“…This result indicates that the states of hydrogen present in the specimens were identical even though different hydrogen charging methods were employed, which is consistent with the previous papers. [7,8] The hydrogen contents charged by the immersion and cathodic electrolysis methods under the conditions used were measured to be 1.3 and 0.9 mass ppm, respectively. The scattering of the hydrogen concentration under the same charging condition was ±0.15 mass ppm.…”

“…Regardless of the type of hydrogen charging method used, the states of hydrogen present in steels are identical under the same charging temperature and hydrogen content. [7,8] However, immersion methods change the surface states of steels [8] and cause the blunting of notches [6] due to corrosion and dissolution, which affect fracture strength in delayed fracture tests. Hydrogen charging and stress application procedures differ among researchers.…”

Effects of Test Conditions on Corrosion Reactions and Hydrogen Absorption in Hydrogen Embrittlement Tests Using an Ammonium Thiocyanate Solution

“…1) The authors previously reported that hydrogen absorption during an immersion test in an NH 4 SCN aqueous solution is affected by corrosion reactions and the resultant corrosion products. 4,5) Reported examples of corrosion reactions of steel materials in an NH 4 SCN aqueous solution include the dissolution of iron as an anodic reaction and a reduction reaction of dissolved oxygen and a simple reduction reaction of protons as cathodic reactions. 1) The authors reported that two types of reactions mainly take place in parallel as cathodic reactions of steel materials in an NH 4 SCN…”