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Abstract
In order to assess the influence of dissolved hydrogen on the intergranular stress corrosion cracking (IGSCC) characteristics of Type 304 stainless steels treated with inhibitive chemicals, electrochemical corrosion potential (ECP) measurements and slow strain rate tensile (SSRT) tests were conducted in high temperature pure water. A number of thermally sensitized specimens were prepared and then pre-oxidized in a 288°C pure water environment with the presence of 300ppb dissolved oxygen for 360h. Most of the specimens were then separately treated with various inhibitive chemicals including powdered zirconium oxide (ZrO2), powdered titanium oxide (TiO2), and zirconyl nitrate [ZrO(NO3)2] via hydrothermal deposition at 150°C. Test environments with a dissolved oxygen concentration of 300ppb and various dissolved hydrogen concentrations at 288°C were created. Test results showed that the ECPs of the treated specimens were lower than that of the untreated one no matter what the dissolved hydrogen concentration was. In addition, IGSCC was observed on all specimens (treated or untreated) in all tested environments. However, the untreated specimen exhibited lower elongation, shorter failure time, and more secondary cracks on the lateral surfaces. It was therefore suggested that inhibitive chemicals such as ZrO2, TiO2, and ZrO(NO2)2 did provide a certain degree of enhancement in improving the mechanical behavior of the treated specimens and in prolonging IGSCC initiation times.