Band 43, Heft 6

International hydrogen pipeline code ASME B31.12 requires the measurement of hydrogen affected fracture toughness using constant load or displacement tests standardized in ASTM E1681. The modified wedge-opening-loaded (WOL) specimen is loaded with a bolt that sets a constant crack mouth opening displacement and the initial stress intensity factor (K Iapp ). In this review paper, the sizing restrictions imposed by the testing procedures are analyzed considering the strength, wall thickness, diameter and toughness of existing and commercially available pipelines. The conclusion is that specimens with the standard geometry for constant displacement test in ASTM E1681 cannot be extracted from most used pipelines. The equations proposed in standards to calculate K Iapp as a function of crack mouth opening displacement cannot be applied and particular expressions must be calculated case by case. Furthermore, loading the specimen to the required K Iapp results in exceedingly large normal stresses in the bolt, increasing the risk of fracture of the bolt during loading of the specimen. Additionally, literature results of pipeline stees tested with the constant displacement in gaseous hydrogen are discussed and their significance is analyzed considering the material performance measured under rising displacement tests in gaseous hydrogen.

In this paper, the research progress of zirconium (Zr) alloys is critically reviewed from the aspects of application, development status, and degradation mechanism in a nuclear environment. The review focused on the application of Zr alloys in the nuclear industry, which are widely used due to their low thermal neutron absorption, good corrosion resistance, and excellent mechanical properties. However, with the increasing requirements in the chemical and medical fields, the application of Zr alloys in these non-nuclear fields is growing due to their excellent properties like good corrosion resistance and low thermal expansion coefficient, as summarized in this review. Additionally, the degradation mechanisms of Zr alloy exposed to a corrosive environment, i.e., corrosion and hydrogen uptake, and the role of alloying selection in minimizing these two phenomena is considered in this review, based on pretransition kinetics and the loss of oxide protectiveness at transition. This is corroborated by the discussion on alloying elements with beneficial and detrimental effects on the corrosion performance of Zr alloys, as well as elements with contradicting effects on Zr alloys corrosion performance owing to the discrepancies in literature. Overall, this review can be leveraged in future alloy design to further improve Zr alloys corrosion resistance in nuclear applications, thus ultimately improving their integrity.

Water-glycol hydraulic fluid (HFC) has been applied in deep-sea hydraulic systems owing to its flame retardant and environmental performance. However, the corrosion characteristics of metals in HFC have not been widely investigated. The electrochemical corrosion behavior of 45# steel and 17-4PH stainless steel in HFC containing four concentrations of seawater (0 %, 3 %, 11 %, 19 %) were evaluated by potentiodynamic polarizations (−800 mV∼1,500 mV vs. Hg/HgO), electrochemical impedance spectroscopy (EIS), potentiostatic polarizations (0.5 V Hg/HgO ) and immersion test (240 h). The research results indicate that a corrosion-resistant carbon film is formed on the surface of 17-4PH stainless steel and 45# steel in HFC. The infrared spectroscopy results suggest that the formation of the carbon film is due to the adsorption of the benzene ring of tolyltriazole (TTA) in HFC by the metal C. 45# steel exhibited stronger corrosion resistance than 17-4PH stainless steel due to the formation of a denser carbon film through high carbon content adsorption. The infiltration of seawater into HFC enhanced its corrosiveness by enhancing its conductivity and Cl − pitting on the C film. This research is significant as it sheds light on the corrosion behavior of metals in HFC, a crucial aspect in the design and maintenance of deep-sea hydraulic systems.

Ti/IrO 2 –Ta 2 O 5 coated anodes were widely used in the production process of aluminum foil that is vital raw material for high-performance electronic components, exhibits excellent service durability in sulfuric acid medium, but its lifespan is significantly reduced when used in ammonium citrate neutral electrolyte. The evolution of constant current accelerated lifetime process of Ti/IrO 2 –Ta 2 O 5 anodes in 100 g/L ammonium citrate aqueous solution was systematically studied. The corrosion mechanism was revealed by physical characterization and electrochemical measurements. During electrolysis, IrO 2 was gradually dissolved due to the interaction of IrO 2 coating and the electrolyte. Consequently, the corrosion mechanism of the compact IrO 2 –Ta 2 O 5 coating is the effect of substantial dissolution of the active components.

Sulfide often appears in circulating cooling water due to the presence of sulfate reducing bacteria and could affect corrosion behavior of cooling pipe metals such as stainless steel. Scanning Kelvin probe and scanning electrochemical microscope measurements, combined with electrochemical testing, were used to investigate the micro-electrochemical information of passive film and analyzed the influence of sulfide in simulated cooling water on corrosion resistance of stainless steel. Results showed that the presence of sulfide in water caused a negative shift in surface potential of stainless steel, an increase in surface potential difference, and an increase in local response current on the surface, resulting in a current peak that gradually increased over time. The analysis results of passive film composition showed that the presence of sulfide caused increase in the ratio of Fe/Cr and OH − /O 2− , as well as the content of Cr(OH) 3 and Fe(OH) 3 in passive film, whereas caused a decrease of Cr 2 O 3 content, and led to the formation of FeS 2 in the passive film. These changes in the composition of the passive film made it easier for active sites to appear on the surface of stainless steel and enhanced the conductivity of the passive film and significantly reducing its protective performance.