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The hydrogen embrittlement (HE) susceptibility of the X52 pipeline steels in simulated hydrogen-blended natural gas (HBNG) environments were investigated with a combination of in situ high-pressure gaseous hydrogen permeation tests, slow strain rate tensile (SSRT) tests and molecular dynamics simulation, the results were compared with the X80 steel. The HE susceptibility of the X52 steel was found higher than that of the X80 steel. The mechanism of the two steels showing different HE susceptibility was analyzed from a point of permeation parameters and molecular dynamics simulation. The results showed that the X52 steel contained more impurity elements and a larger grain size, leading to a higher hydrogen solubility and a microstructure with lower HE resistance. This study suggests that the steel microstructure and the hydrogen permeation property are crucial for the understanding and prediction of the HE susceptibility of the steels. • N 2 partial pressure would not influence the hydrogen permeation behaviour. • HE susceptibility is not necessarily positively correlated with steel grade. • Phase transition/dislocation emission is main deformation mechanism of boundaries. • Hydrogen atom inhibit local energy release and promote crack initiation. • Finer grain weakens the inhibition of local energy release caused by H. [ABSTRACT FROM AUTHOR]

Hydrogen permeation through uniaxially strained thin SiO x based gas barrier films, formed at room temperature and ambient pressure on PET foil substrates by UV photochemical conversion (Photoconversion), was investigated using a dedicated measurement system. Hydrogen permeation measurements were conducted as a function of the stack of laminated single SiO x barrier films, of the sample temperature as well as of the uniaxial mechanical strain applied to the samples. The results demonstrate a significant overall improvement of the hydrogen barrier properties for both single SiO x barrier films on PET and laminated single SiO x barrier films on PET. In the case of strained samples, the hydrogen barrier properties deteriorate due to stress-induced crack formation in the barrier films. This deterioration is strongest for strained single SiO x barrier films but can be substantially reduced by laminating single SiO x barrier films. • Hydrogen permeation measurements as a function of sample strain and temperature • Use of a dedicated hydrogen permeation measurement system for strained samples • Hydrogen permeation through thin SiO x gas barrier films on PET foil substrates • SiO x barrier films formed by UV photochemical conversion of perhydropolysilazane • Hydrogen barrier improvement for single and laminated SiO x barrier films on PET [ABSTRACT FROM AUTHOR]

P91 steel (X10CrMoVNb9-1) is widely used in the energy industry. It is characterized by good mechanical properties, creep resistance, corrosion resistance, impact toughness, and resistance to thermal fatigue. Due to their operating conditions and martensitic structure, components made from P91 steel are often subject to damage related to the presence of hydrogen. This article compares the results of the mechanical properties evaluation for P91 steel in an aggressive solution charged under load and without load. Based on the research, it was found that the hydrogen environment significantly affects the mechanical properties of P91 steel, reducing strength and yield strength, and decreasing ductility. It was revealed that in samples tested after 72 h without preloading, the tensile strength decreased by 1.5%, and the elongation decreased by about 29% for the sample, compared to the delivered condition sample. Under loaded conditions, the difference in tensile strength increased by approximately 8%, while elongation increased by nearly 50% [ABSTRACT FROM AUTHOR]

Carbon steel piping and tubing can be degraded by hydrogen uptake. The hydrogen permeation method is commonly applied to testing and qualification steel in response to hydrogen atom diffusion. Cyclic voltammetry (CV) has recently been proposed because it is a more straightforward method than permeation. A comprehensive study was conducted to investigate whether these two methods are comparable. A model alloy of SA 210 grade was studied. The study involved preparing specimens with varying microstructures through different heat treatments. Subsequently, metallographic analysis was conducted on each microstructural variation, followed by mechanical testing to evaluate the changes obtained before and after the hydrogen absorption test. The CV method consisted of three steps: CV before H absorption to search for a reference voltammogram, H charging, and CV after H absorption to determine the after-charge voltammogram. Electrochemical hydrogen permeation tests were performed in a Devanathan–Stachursky double cell. A comparison of the CV and permeation methods revealed that they show pretty similar results in evaluating the interaction between steel and hydrogen. Permeation methods provide quantitative results, while CV offers more qualitative insights. Both methods show that the quenched steel has the slowest hydrogen diffusion rate compared with those in normalized and base material conditions. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to assess the hydrogen embrittlement sensitivity of carbon gradient heterostructure materials and to verify the reliability of the scratch method. Design/methodology/approach: The surface-modified layer of 18CrNiMo7-6 alloy steel was delaminated to study its hydrogen embrittlement characteristics via hydrogen permeation, electrochemical hydrogen charging and scratch experiments. Findings: The results showed that the diffusion coefficients of hydrogen in the surface and matrix layers are 3.28 × 10−7 and 16.67 × 10−7 cm2/s, respectively. The diffusible-hydrogen concentration of the material increases with increasing hydrogen-charging current density. For a given hydrogen-charging current density, the diffusible-hydrogen concentration gradually decreases with increasing depth in the surface-modified layer. Fracture toughness decreases with increasing diffusible-hydrogen concentration, so the susceptibility to hydrogen embrittlement decreases with increasing depth in the surface-modified layer. Originality/value: The reliability of the scratch method in evaluating the fracture toughness of the surface-modified layer material is verified. An empirical formula is given for fracture toughness as a function of diffused-hydrogen concentration. [ABSTRACT FROM AUTHOR]

In order to study the effect of heat treatment in air on the hydrogen permeation in/through Pd membrane, Pd membrane was deposited via the electroless plating method and the hydrogen permeation flux of Pd membrane before and after heat treatment in air at 573 K was measured. The membranes were characterized by XRD, SEM, AFM and hydrogen permeation tests. The results show that Pd membrane is compact and defect-free and has a thickness of 5 μm. The hydrogen permeability of Pd membrane at 673 K, 723 K and 773 K are 3.62×10-9, 5.12×10-9 mol/(m·s·Pa0.5) and 6.80×10-9 mol/(m·s·Pa0.5), respectively. The membrane treated in air at 573 K has higher surface roughness, larger surface area and more dissociation adsorption sites than the as-deposited membrane, thus improving the hydrogen permeability of the Pd membrane. After heat treatment, the hydrogen permeability of Pd membrane at 673, 723 K and 773 K are 5.32×10-9, 6.44×10-9 mol/(m·s·Pa0.5) and 7.31×10-9 mol/(m·s·Pa0.5), respectively. The hydrogen permeability of such Pd membrane is 1.1-1.5 times higher than that of the as-deposited one.

Microstructure is an important factor affecting hydrogen diffusion in pipeline steels. Due to the different stress and heat conditions, the surface and internal microstructure of the rolled pipeline steels is different. The ferrite grain size in surface layer of X42 pipeline steel is smaller than other locations, while the surface layer of X52 pipeline steel has continuous banded ferrite/pearlite structure and grains with uneven size. Hydrogen permeation behavior is investigated at different positions in the normal direction of X42 and X52 pipeline steels using the electrochemical hydrogen permeation technique. The results show that the values of the effective diffusion coefficient of surface layer in X42 and X52 pipeline steels are the smallest, while the values of the subsurface hydrogen concentration at steady state are the largest. Hydrogen microprint experiment results indicate hydrogen atoms mainly escape at pearlite, ferrite grain boundaries and near inclusions in X42 and X52 pipeline steels. • The surface and interior microstructure of rolled pipeline steel is inconsistent. • Hydrogen diffusion is hindered by grain boundaries. • The continuous banded ferrite/pearlite structure impedes hydrogen diffusion. • Hydrogen atoms mainly escape at pearlite and ferrite grain boundaries. [ABSTRACT FROM AUTHOR]

In this work, passivation of X80 pipeline steel was established at various passive potentials in a carbonate/bicarbonate solution. The passive films were characterized by topographical, compositional, and structural analysis techniques and electrochemical measurements. The effect of the passive film on hydrogen (H) atom permeation was investigated by electrochemical H permeation testing and scanning Kelvin probe force microscopy. The passive films primarily comprise Fe 2 O 3 /Fe 3 O 4 and FeOOH. In the stable passive region, notably at 0.25 V (saturated calomel electrode, SCE), the formed passive film exhibits the highest film resistance, and the smallest double-layer capacitance and donor density. In contrast, oxide films formed at −0.1 V(SCE) and 0.55 V(SCE), which close to the active-passive transition and the transpassive regions, respectively, differ in their characteristics. The oxide films formed at −0.1 V(SCE) and 0.25 V(SCE) exhibit resistance against H atom permeation, and a superior performance is observed in the film formed at 0.25 V(SCE). The oxide film formed at 0.55 V(SCE) exhibits increased H atom permeation, which is attributed to the degraded structure of the film. Thus, the presence of compact oxide film (scale) on steel surface can effectively inhibit H atom permeation into the steel. • Prepared oxide films with various structures and morphologies on the surface of X80 pipeline steel. • Determined the role of oxide film in inhibition of hydrogen atom permeation into the steel. • Proposed an index to evaluate the inhibition performance of the oxide film in resistance to hydrogen permeation. [ABSTRACT FROM AUTHOR]

In order to accurately determine the mass balance of hydrogen in steel sheet in electrochemical hydrogen permeation tests, channel flow double electrode (CFDE) technique was combined with the Devanathan-Stachurski (DS) cell. One side of a steel sheet was used as the hydrogen entry electrode in the DS cell and as the generator electrode in the CFDE. The back side of the steel sheet was anodically polarized in NaOH solution for hydrogen withdrawal, and anodic polarization of the platinum detector electrode for CFDE was performed for molecular hydrogen that did not enter the steel sheet while cathodic polarization of the hydrogen entry electrode in Na 2 SO 4 solution. The mass balance obtained from the mass of adsorbed hydrogen, the mass of permeated hydrogen, and the mass of evolved hydrogen enabled quantitative analysis of the hydrogen un-permeated in the steel sheet. • CFDE-DS cell was developed to quantify non-adsorbed hydrogen in sample membrane. • Mass balance of hydrogen during permeation test was considered for the first time. • Hydrogen absorption reaction on entry side electrode proceeds in Volmer process. • Mass of hydrogen absorbed at entry interface was fixed after irreversible trapping. [ABSTRACT FROM AUTHOR]

The use of hydrogen-blended natural gas presents an efficacious pathway toward the rapid, large-scale implementation of hydrogen energy, with pipeline transportation being the principal method of conveyance. However, pipeline materials are susceptible to hydrogen embrittlement in high-pressure hydrogen environments. Natural gas contains various impurity gases that can either exacerbate or mitigate sensitivity to hydrogen embrittlement. In this study, we analyzed the mechanisms through which multiple impurity gases could affect the hydrogen embrittlement behavior of pipeline steel. We examined the effects of O2 and CO2 on the hydrogen embrittlement behavior of L360 pipeline steel through a series of fatigue crack growth tests conducted in various environments. We analyzed the fracture surfaces and assessed the fracture mechanisms involved. We discovered that CO2 promoted the hydrogen embrittlement of the material, whereas O2 inhibited it. O2 mitigated the enhancing effect of CO2 when both gases were mixed with hydrogen. As the fatigue crack growth rate increased, the influence of impurity gases on the hydrogen embrittlement of the material diminished. [ABSTRACT FROM AUTHOR]

X80 pipeline steel has played a vital role in oil and gas transportation in recent years. However, hydrogen-related issues frequently lead to pipeline failures during service, resulting in significant losses of properties and lives. Three heat treatment processes (furnace cooling (FC), air cooling (AC), and water cooling (WC)) were carried out to investigate the effect of different microstructures on hydrogen-induced cracking (HIC) susceptibility of X80 pipeline steel. The WC sample demonstrated the highest hydrogen embrittlement index, registering at 21.9%, while the AC and FC samples exhibited progressively lower values of 15.45% and 10.98%, respectively. Under equivalent hydrogen charging durations, crack dimensions with a maximum length exceeding 30 μm in the WC sample generally exceed those in the FC sample and AC sample. The variation is attributed to the difference in microstructures of the samples, predominantly lath bainite (LB) in water-cooled samples, granular bainite (GB) in air-cooled samples, and ferrite/pearlite (F/P) in FC samples. The research results demonstrate that the sensitivity of lath bainite (LB) to HIC is significantly higher than that of pearlite, ferrite, and granular bainite (GB). The presence of a large amount of martensite/austenite (M/A) constituents within bainite results in a multitude of hydrogen trap sites. HIC cracks in bainite generally propagate along the profiles of M/A constituents, showing both intergranular and transgranular cracking modes. [ABSTRACT FROM AUTHOR]

Hydrogen diffusivity can play a crucial role in hydrogen-assisted degradation of steels. Herein, we investigate the hydrogen diffusion behavior in two X65 pipeline steels using desorption and permeation techniques. Gas charged samples were used for desorption experiments, while permeation tests were conducted using electrochemical charging. The Vintage steel, having a banded ferrite-pearlite microstructure, exhibits a significant influence of strong traps. A modified solution of Fick's 2nd law is proposed to account for the strong traps. At room temperature, the effective diffusivity in the Modern steel, which has homogenous ferrite-bainite microstructure, has a scatter factor of three, whereas for the Vintage steel, the factor is 17. The difference is explained by considering a concentration-dependent effective diffusivity and a tortuous diffusion path. Comparable values of the highest measured effective diffusivity at room temperature were obtained for the Modern and Vintage steels: 2.70 × 10−6 and 3.34 × 10−6 cm2/s, respectively. • Effect of microstructure, technique, and charging condition on measured diffusivity evaluated. • A modified solution to Fick's 2nd law was proposed to account for strong traps. • Significance of method used to determine effective diffusivity varied with steel. • Multiple major trap sites are present in the banded ferrite-pearlite microstructure. • Pearlite bands with low diffusivity can cause a tortuous diffusion path. [ABSTRACT FROM AUTHOR]

This study investigates the creep-fatigue behavior of recrystallized zirconium alloy at 320 °C and different hydrogen contents using frequency-corrected strain life and frequency-corrected hysteresis energy methods. The results indicate that as the holding time increases, the creep-fatigue resistance of the non-hydrogen permeation sample decreases, but there is no significant effect when holding time exceeds 30 s. However, the effect of holding time on the creep-fatigue resistance of hydrogen permeation sample is not significant. It was found that the non-hydrogen permeation sample had the best creep-fatigue resistance, while the 0.04% hydrogen permeation sample had the worst resistance. The creep-fatigue resistance of the 0.005% hydrogen permeation sample was weaker at high strain levels (high hysteresis energy) than that of the 0.02% hydrogen permeation sample, and better than that of the 0.02% hydrogen permeation sample at low strain levels. The effect mechanism of hydrogen content on creep-fatigue behavior: solid solution hydrogen can increase creep-fatigue life, while hydrides can reduce creep-fatigue life. The hydride plays a dominant role in the sample with hydrogen content of 0.04%, resulting in the worst creep-fatigue performance. [ABSTRACT FROM AUTHOR]

This work aims to demonstrate that the resistance to hydrogen embrittlement of conventional advanced high-strength steel (AHSS) with a bainitic ferrite structure can be significantly enhanced through two metallurgical strategies. Firstly, a smaller fraction of cementite in a mixture of bainitic ferrite and lath-martensite structures is realized by an intercritical annealing process with rapid cooling. Secondly, a higher fraction of alloy carbides (MC) with a mean size of less than 30 nm is formed through the combined addition of Ti, Mo, and V as micro-alloying elements. The reduction of cementite precipitation in the matrix leads to an increased resistance to hydrogen evolution/adsorption on the surface under cathodic polarization. Moreover, a large number of V-bearing nanoprecipitates ((Ti,Mo,V)-carbides and V-carbides) provides intermediate trapping for hydrogen atoms, effectively delaying the diffusion kinetics of hydrogen towards potential crack-forming areas in the matrix. Consequently, the lower strain reduction during slow strain rate test and the higher resistance to cracking during the four-point bending test in acidic aqueous solutions are manifested in the newly designed AHSS.

In this study, we systematically investigate electrochemical hydrogen charging conditions equivalent to hydrogen gas pressures relevant for hydrogen transportation in X65 pipeline steel. By performing hydrogen gas permeation, a relationship for Sieverts' law was established, which was used in combination with electrochemical hydrogen permeation to determine the equivalent hydrogen pressure. The results revealed that cathodic protection simulated condition at –1050 mVAg/AgCl was equivalent to a hydrogen pressure of 12.3 bar. The addition of thiourea, a hydrogen recombination poison, and changing the applied potential in the cathodic direction increased the equivalent hydrogen pressure. In this way, an electrochemical charging condition equivalent to a potential hydrogen gas pressure for hydrogen transportation (200 bar) was determined. [ABSTRACT FROM AUTHOR]

In the hydrogen separation membrane, a dense TaTiNbZr amorphous layer was prepared between Pd and Ta to form a Pd/TaTiNbZr/Ta membrane system to prevent the reaction between Pd and Ta at high temperatures. The structural and chemical stability of the Pd/TaTiNbZr/Ta film system at high temperatures were investigated by annealing at 600 °C for 24 h. The high-temperature hydrogen permeation properties of the Pd/TaTiNbZr/Ta film systems were investigated by hydrogen permeation experiments at 600 °C after heat treatment for 6 h. The TaTiNbZr layer was significantly hydrogen-permeable. With the increase in the thickness of the barrier layer, the hydrogen permeability of Pd/TaTiNbZr/Ta decreased, but its hydrogen permeation flux was smaller than that of the highest value of Pd/Ta when it reached the steady state. The presence of the TaTiNbZr layer effectively blocks the interdiffusion between Pd and Ta to form TaPd3, improving the sustained working ability of the Pd/TaTiNbZr/Ta membrane system. The results show that TaTiNbZr is a candidate material for the intermediate layer to improve the high-temperature stability of metal-composite hydrogen separation membranes. [ABSTRACT FROM AUTHOR]

Proton exchange membrane (PEM) water electrolysis presents a blueprint for high-efficiency green hydrogen production. However, hydrogen (H2) permeation across the PEM poses challenges to the efficiency and safety of PEM water electrolysis. Herein, we investigated the hydrogen permeation process on the prepared perfluorinated sulfonic acid (PFSA) membrane with a thickness range from 50 μm to 180 μm, demonstrating the influence mechanism of PEM structure on hydrogen permeation. Five kinds of perfluorinated sulfonic acid PEM with different thickness were cast from Nafion D520 dispersion into quartz vessels. Membrane electrode assembly (MEA) was assembled into a single cell by a hot press transfer method. Electrochemical tests and gas chromatography were used to validate the influence of the thickness of PEM on the cell performance and H2 permeation of PEM water electrolysis. The permeation of H2 is not simply inversely proportional to the thickness of the films, which may be due to structural differences between films. To further elucidate the modulating mechanism of PEM structure on H2 permeation, the relative crystallinity of the membrane and the mean spacing between the hydrophilic water-domains were tested through X-ray diffraction and scattering experiments. Additionally, grey correlation analysis (a mathematical statistical analysis method) was performed on the collected data. The analysis revealed the prominent modulating effect of the membrane structure parameters (water content (S), crystallinity (Xc) and water-domains spacing (Dw) on the H2 permeation, with Dw identified as the primary factor affecting H2 permeation. These parameters influence the size and connectivity of the hydrophilic water-domains within the membrane impacting the size and length of the H2 diffusion path and resulting in differences in hydrogen diffusion rate. This study aimed to investigate the influence mechanism of proton exchange membrane structure on hydrogen permeation, offering fresh perspectives on research into the hydrogen permeation performance of proton exchange membranes. Our study offers a guidance for researchers in the development of cost-effective and secure membranes for use in PEM water electrolysis. [ABSTRACT FROM AUTHOR]

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With the international drive to deploy green energies and decarbonized intermediates in the place of fossil fuel sources, a large number of developed countries are actively preparing for a future where hydrogen plays a strategic role as an energy storage medium. Producing and using hydrogen requires the rapid expansion of a dedicated, economically viable industrial sector. Nevertheless, questions on how to safely store, transport and distribute hydrogen remain an important priority today. In countries with existing natural gas transport grids, the possibility to retrofit these networks to store and transport hydrogen-natural gas blends is being studied. A key challenge is to evaluate how pressurized H 2 would interact with steel structures with regards structural embrittlement of the latter, with a view to exploiting existing transport infrastructures for storage and transport applications. In this work, we evaluate the H 2 -performance of a non-hydrogen service ×65 pipeline steel. The cracking susceptibility of this steel grade has been evaluated at 100 bar H 2 using slow strain rate testing, Constant strain testing and fracture toughness measurements. Accompanying hydrogen permeation tests under pressure provide diffusion data and elucidate the discussion. Exposures were carried out in dry or wet H 2 and with or without H 2 S contamination at levels representative of biogas. The results underline that the impact of dry or wet hydrogen on this grade are moderate. The presence of traces of H 2 S together with humidity could risk seriously degrading the mechanical performance of the ×65 steel grade. • The risk of hydrogen assisted cracking is low with ×65 up to 100 bar H 2 in the absence of gas contaminants. • The decrease in fracture toughness is minimal under dry H 2 even though some embrittlement is visible in the fractured surface. • The fracture toughness in gaseous H 2 significantly decreases in presence of humidity with traces of H 2 S. • The extent of hydrogen induced cracking, even in the in presence of humid H 2 S contamination, remains low. • The hydrogen ingress assessed through TDS measurement was extremely low. [ABSTRACT FROM AUTHOR]

Blow molded plastic liners (BMPLs) for on-board Type IV compressed gaseous hydrogen (CGH2) storage tanks consist of a high-molecular-weight polymer wall that serves as a permeation layer for hydrogen gas. This paper presents the latest numerical model integrated in the Blow View software for predicting the hydrogen permeation in a BMPL. The prediction model is based on Fick's solution-diffusion laws, with pressure and temperature dependent transport properties, for steady/unsteady state permeation regimes through a polymeric wall. An overview of key simulation results for an industrial BMPL for a CGH2 tank, as well as the adopted methodology addressing the challenge to optimize the wall thickness for light weighting and permeability performance, are also presented. • Numerical model for H 2 permeation in homogeneous amorphous polymeric liner. • Fick's solution-diffusion model with pressure and temperature dependent transport properties. • Simulation tool for the design, manufacturing and optimization of BMPL for a CGH2 tank. • BMPL optimization to improve the thickness uniformity for light weighting. • BMPL permeability prediction based on the thickness distribution and material selection. [ABSTRACT FROM AUTHOR]

To attain a lightweight structure with high pressure and a high hydrogen storage mass ratio, the type IV hydrogen storage tank is the most popular choice for many fuel cell vehicle enterprises. Using polymer as the liner material prevents hydrogen embrittlement and hydrogen-induced damage of the tanks, but hydrogen permeation is inevitable. Within the service conditions (233–358 K, 0–87.5 MPa) of the Type-IV tanks, the dissolution and diffusion behaviors of H 2 in polyamide 6 are comprehensively explored for the first time through the molecular dynamics and Grand Canonical Monte Carlo simulations in this study. The diffusion mechanism of H 2 in polyamide 6 is further revealed. The results show that both the diffusion and permeability coefficients have positive correlations with temperature, whereas the opposite is true for the solubility coefficient. These relationships are all consistent with Arrhenius's law in the temperature range, although multiple Arrhenius regions are needed to describe them. A slight decrease in the diffusion and permeability coefficients is observed with increasing pressure. However, this effect is not as significant as that of temperature and can be ignored when the pressure range is narrow enough. The "hopping" mechanism can be used to describe the diffusion of H 2 in polyamide 6, where the continuous vibrations and "hopping" allow the diffusion of H 2 molecules. These findings will contribute to a more comprehensive understanding of the permeation behavior of H 2 in polyamide 6 and evaluate the gas barrier property of the material in practical applications. • The dissolution and diffusion behaviors of H 2 in PA6 are explored by MD and GCMC simulations. • The "hopping" mechanism can describe the diffusion of H 2 in PA6. • Multiple Arrhenius regions are observed under service conditions. • The effect of pressure on permeability is not as significant as that of temperature. [ABSTRACT FROM AUTHOR]

Submarine pipeline are often exposed to the risk of hydrogen embrittlement from the dual action of marine sulfate-reducing bacteria (SRB) and cathodic protection (CP). In this work, hydrogen permeation test, slow strain rate tensile (SSRT) experiments, and density functional theory (DFT) were used to explain the hydrogen embrittlement (HE) mechanism of subsea pipeline steel under the action of SRB and CP. When the applied CP potential is increased from −850 mV to −1200 mV, the hydrogen seepage current increases 1.8 times. And the tensile specimens pre-charged with hydrogen exhibit significant hydrogen embrittlement behavior. DFT calculations show that the increased concentration of hydrogen atoms on the material surface decreases the diffusion potential barrier, leading to a larger hydrogen seepage current. In addition, the aggregation of hydrogen atoms in the steel weakens the chemical bonds between Fe atoms, leading to hydrogen embrittlement. • Combining experimental and DFT techniques to investigate the HIC behavior of X70 steel. • SRB and cathodic potential enhanced hydrogen permeation. • Hydrogen weakens the iron bonding energy and destroys the metal structure. • The HIC sensitivity rises with increasing hydrogen concentration. [ABSTRACT FROM AUTHOR]

P91 steel (X10CrMoVNb9-1) is widely used in the energy industry. It is characterized by good mechanical properties, creep resistance, corrosion resistance, impact toughness, and resistance to thermal fatigue. Due to their operating conditions and martensitic structure, components made from P91 steel are often subject to damage related to the presence of hydrogen. This article compares the results of the mechanical properties evaluation for P91 steel in an aggressive solution charged under load and without load. Based on the research, it was found that the hydrogen environment significantly affects the mechanical properties of P91 steel, reducing strength and yield strength, and decreasing ductility. It was revealed that in samples tested after 72 h without preloading, the tensile strength decreased by 1.5%, and the elongation decreased by about 29% for the sample, compared to the delivered condition sample. Under loaded conditions, the difference in tensile strength increased by approximately 8%, while elongation increased by nearly 50%

This paper investigated the effects of welding and alternating wet-dry seawater on the hydrogen embrittlement (HE) susceptibility of a new nanoparticle-reinforced high-strength steel, dispersion-strengthened-high-strength (DSHS) steel. The results show that welding led to the transformation of granular bainite to tempered martensite. It also promotes grain coarsening as well as an increase in inclusions size and irregular changes in shape. This results in increased susceptibility to HE at the welded joint (WJ). After wet-dry cycle corrosion in seawater, corrosion products impede the oxygen transfer and promote the hydrogen evolution reaction, so the hydrogen production increases. The decrease in the protection of corrosion products at the WJ and the decrease in NbC content led to an increase in hydrogen production but a decrease in hydrogen trapping capacity. Therefore, the WJ HE sensitivity of DSHS steel is further increased. • The effect of welding and alternating wet-dry environment on the HE of DSHS steels was studied. • Simulation of hydrogen permeation under alternating wet-dry environment using a modified Devanathan-Stachurski cell. • The microstructure and inclusions are the main factors affecting the HE of the material in its initial state. • Hydrogen production is the main factor for the susceptibility of DSHS steels to HE under alternating wet-dry environment. [ABSTRACT FROM AUTHOR]

To better understand hydrogen uptake kinetics, electrochemical permeation tests have been performed in a quenched and tempered low-alloy steel. Hydrogen uptake and transport has been studied with three different surface roughness, in four different solutions (1 M H 2 SO 4 , 1 M H 2 SO 4 +As 2 O 3 , 0.1 M NaOH and 3.5% NaCl) and two different hydrogen charging current densities (1 and 5 mA/cm2). A strong effect of the charging solution, current density and surface roughness has been demonstrated. In 1 M H 2 SO 4 + As 2 O 3 solution and 5 mA/cm2, hydrogen recombination on the surface of the samples is strongly reduced and interstitial diffusion prevails due to the trap saturation (D L ≈ D a p p ). However, in 1 M H 2 SO 4 , 0.1 M NaOH and 3.5% NaCl, hydrogen transport is dominated by trapping and detrapping processes (D L > D a p p ). Permeation transients are numerically reproduced through Finite Element simulations and compared to the experimental results. The relationship between hydrogen diffusion kinetics at the microstructural level and surface effects is clearly established by a mapping strategy obtained from the wide range of experimental results, combined with a numerical approach. • Hydrogen entry is influenced by the charging solution, current density and roughness. • Apparent diffusion coefficient of hydrogen depends on hydrogen concentration. • Entry flux is reproduced from HER and absorption theory. • Finite element framework has been developed to reproduce permeation tests. [ABSTRACT FROM AUTHOR]

An attempt is made to visualize hydrogen permeation through vanadium membranes using operando hydrogen microscopy. Prior to visualization, experimental conditions are determined. The vanadium sample surface for hydrogen introduction is coated with Pd-25 mol％Ag alloy. Also, the optimal temperature of the vanadium sample for hydrogen visualization is determined. By optimizing the experimental conditions, some correlation was found between the distribution of permeated hydrogen and the morphology of vanadium particles observed in secondary electron image of scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Hydrogen permeation technique is a widely used testing method for the determination of hydrogen diffusion coefficient (D), which is an important parameter considering hydrogen embrittlement. A palladium (Pd) or nickel (Ni) coating is often utilised on the hydrogen detection side of the test specimens. Here, we investigate the effect of Pd and Ni coatings on hydrogen diffusion in a martensitic 500 HBW hardness low-alloy steel in the thickness range of 0.5 – 0.8 mm using a refined successive transient method and compare against an uncoated reference specimen. Both coatings yield similar average D values (6 – 6.6 × 10−7 cm2/s), but the best repeatability is achieved with Pd coating. With Ni coating, D values decrease with the increasing specimen thickness, which is partly caused by a slower hydrogen diffusion in Ni, and therefore a concentration gradient at the specimen-coating interface. The uncoated specimen has a poor transient fit, and significantly lower D (2.1 × 10−7 cm2/s) due to surface oxidation. With both coatings, the steepness of the last decay transient was highly affected by specimen thickness, and therefore the density of reversible hydrogen traps is only comparable for similar thicknesses. [ABSTRACT FROM AUTHOR]

In this work, electrochemical tests were performed to measure hydrogen permeation during free dissolution of carbon steel in the presence of the ionic liquids (ILs) 1-ethyl-3-methylimidazolium acetate [(EMIM)+(Ac)-], 1-ethyl-3-methylimidazolium bromide [(EMIM)+(Br)-], and 1-butyl-3-methylimidazolium tetrafluoroborate [(BMIM)+(BF4)-] in 5.4 mol L-1 HCl aqueous solution. The permeation inhibition efficiencies (IEp (%)) of 5-hydroxy-2-nitromethylene-hexahydropyrimidine (HPY) and a commercial corrosion inhibitor (CCI) were also evaluated. Among the ILs, the (BMIM)+(BF4)- compound presented the highest corrosion and hydrogen permeation inhibition efficiencies, with values of 23% and 30%, respectively. The (EMIM)+(Br)- and (EMIM)+(Ac)- compounds were not effective against corrosion, but they presented IEp of 15.8% and 23%, respectively. The HPY compound demonstrated 61% effectiveness in preventing corrosion, while in silico evaluation indicated no toxicity. However, neither the HPY compound nor the CCI compound inhibited the entry of hydrogen into the carbon steel during the pickling process.

Hydrogen embrittlement is a serious phenomenon resulting in severe ductility deterioration of engineering materials due to the presence of hydrogen atoms. The low concentration of dissolved oxygen in deep-sea provide the condition for hydrogen production. Herein, the hydrogen permeation behavior in X70 pipeline steel in acid/alkaline environment under different hydrostatic pressure were investigated via electrochemical hydrogen permeation parameters. The results revealed the different trends of i∞ with increasing hydrostatic pressure. The phenomenon was described from the perspectives of hydrogen generation, absorption/desorption and permeation process by potentiodynamic polarization, linear sweep voltammetry (LSV) and EIS tests. The experimental permeation data were fitted with surface effect model and leads to the conclusion that the hydrostatic pressure greatly enhanced the adsorption rate and restricts the desorption rate of absorbed hydrogen atoms on the metal surface, thereby the process of atomic hydrogen compounding into hydrogen molecules is inhibited, leading to an increase in sub-surface hydrogen concentration (C0).

The effect of La3+ on the hydrogen permeation behavior of 27CrMo44S/1 steel in acidic environments containing H2S is investigated through the measurement of steady-state permeation current density (i∞), hydrogen diffusivity (D), and subsurface hydrogen concentration (C0). Results indicate that the addition of La3+ can remarkably reduce i∞. The corrosion products with La3+ involved in the film formation process in the H2S-free environment have a good hydrogen barrier effect, but the addition of La3+ hardly influence the D value of 27CrMo44S/1 steel in the H2S-containing environment. However, the presence of La3+ substantially reduces the C0 on metal surface regardless of the presence of H2S in the solution. Static immersion and tensile experiments illustrate that the addition of La3+ can improve the corrosion resistence and plasticity loss of the material in the H2S environment.

The use of hydrogen-blended natural gas presents an efficacious pathway toward the rapid, large-scale implementation of hydrogen energy, with pipeline transportation being the principal method of conveyance. However, pipeline materials are susceptible to hydrogen embrittlement in high-pressure hydrogen environments. Natural gas contains various impurity gases that can either exacerbate or mitigate sensitivity to hydrogen embrittlement. In this study, we analyzed the mechanisms through which multiple impurity gases could affect the hydrogen embrittlement behavior of pipeline steel. We examined the effects of O2 and CO2 on the hydrogen embrittlement behavior of L360 pipeline steel through a series of fatigue crack growth tests conducted in various environments. We analyzed the fracture surfaces and assessed the fracture mechanisms involved. We discovered that CO2 promoted the hydrogen embrittlement of the material, whereas O2 inhibited it. O2 mitigated the enhancing effect of CO2 when both gases were mixed with hydrogen. As the fatigue crack growth rate increased, the influence of impurity gases on the hydrogen embrittlement of the material diminished.

X80 pipeline steel has played a vital role in oil and gas transportation in recent years. However, hydrogen-related issues frequently lead to pipeline failures during service, resulting in significant losses of properties and lives. Three heat treatment processes (furnace cooling (FC), air cooling (AC), and water cooling (WC)) were carried out to investigate the effect of different microstructures on hydrogen-induced cracking (HIC) susceptibility of X80 pipeline steel. The WC sample demonstrated the highest hydrogen embrittlement index, registering at 21.9%, while the AC and FC samples exhibited progressively lower values of 15.45% and 10.98%, respectively. Under equivalent hydrogen charging durations, crack dimensions with a maximum length exceeding 30 μm in the WC sample generally exceed those in the FC sample and AC sample. The variation is attributed to the difference in microstructures of the samples, predominantly lath bainite (LB) in water-cooled samples, granular bainite (GB) in air-cooled samples, and ferrite/pearlite (F/P) in FC samples. The research results demonstrate that the sensitivity of lath bainite (LB) to HIC is significantly higher than that of pearlite, ferrite, and granular bainite (GB). The presence of a large amount of martensite/austenite (M/A) constituents within bainite results in a multitude of hydrogen trap sites. HIC cracks in bainite generally propagate along the profiles of M/A constituents, showing both intergranular and transgranular cracking modes.

Hydrogen embrittlement is a diffusible Hydrogen that is harmful to the toughness of iron. It follows, therefore, that the harmful influence of diffusible Hydrogen can be mitigated by preventing its entry into steel. This approach was achieved by usingthree coating layersas a coating nanostructure thin layer by DC sputtering on steel structural (AISI l018) and hydrogen charging (HC) effect on uncoated and different Nano coated tensile specimens. The first layer was Titanium as a bonding layer, the second layer was TiO2 with Al2O3, and the third layer was Al2O3. Using a titanium Nano layer coating on AISI1018 steel tensile specimens increased the tensile strength from 570 to 659 MPa with 16 hours of charging, which is considered a good increase. In contrast, the elongation remained in a steady-state with little difference in values compared to changing the charging time and the coating of the double layer. Furthermore, it was found that samples coated with TiO2 and Al2O3 by the DC method had advanced hydrogen embrittlement resistance and increased tensile strength (from 565 to 680 MPa with 8 hours of charging process). Moreover, the maximum adhesion value was related to the triple layer at 596 psi, and the lowest value was 309 psi using the titanium layer alone. The coating time was 5 hours of the sputtering process for all specimens. Thecoating layers are considered a good barrier for hydrogen permeation through steel structures (AISI 1018).

In this paper, hydrogen diffusion behavior in pipeline steel is thoroughly investigated. The effect of various microstructural factors affecting hydrogen diffusion are discussed using literature review. The results of this survey show that the hydrogen diffusion in pipeline steels depends strongly on the microstructure of steel, crystallographic texture, dislocation density, grain size, presence of different elements, precipitates and inclusions. Based on the results, the interfaces between the retained austenite and martensitic layer are considered as the possible hydrogen trap sites. Moreover, the apparent diffusivity decrease due to hydrogen trapping by dislocations is well documented without need for cyclic loading. The grain size and nature of grain boundaries plays an important role in the hydrogen diffusion and trapping. There is an optimum grain size in which the hydrogen diffusion reaches its maximum value. Various elements, inclusions and precipitates which are present in the microstructure of pipeline steel have a considerable role in hydrogen diffusion. Based on the hydrogen microprint technique results, the increase in the grain size decreases the hydrogen trapping by triple junctions and grain boundaries.

The risk of hydrogen embrittlement (HE) and stress corrosion cracking (SCC) is a strong concern for material selection in the oil and gas sector. The presence of H2S enhances hydrogen charging, which can increase hydrogen embrittlement (HE) susceptibility. There are knowledge gaps about HE in the environment saturated with pure carbon dioxide (CO2) and with CO2 containing H2S. CO2 has a strong impact on corrosion rate as well, enhancing cathodic reactions. CO2 might also have a direct contribution to hydrogen charging and cracking mechanisms. This study addresses the assessment of hydrogen permeation and HE of X65 and X80 steels in CO2 and/or H2S environments. The performance of both steel grades is investigated, supported by experimental approach. The results indicate that the loss of mechanical resistance is due to hydrogen uptake and diffusion as well as the anodic dissolution, especially in Solution B. It is observed that X80 steel used in this work is more susceptible to cracking than X65 steel even in pure CO2. It is concluded that the advantage of using a higher‐mechanical‐resistant steel, X80 can be suppressed by HE effects. [ABSTRACT FROM AUTHOR]

The inhibitory effect of La 3 + on the hydrogen permeation of X70 pipeline steel was investigated via steady-state hydrogen permeation current (i 8) through electrochemical hydrogen permeation tests. The experimental permeation data were fitted with a constant concentration model and Electrochemical Impedance Spectroscopy (EIS) tests were conducted to characterize the activity of Hydrogen Evolution Reaction (HER) after the optimization of electrochemically active surface area. Additionally, the kinetics of HER and the adsorption/desorption process is calculated by Iyer-Pickering-Zamanzadeh (IPZ) and surface effect models, of which the results demonstrate that the La 3 + in the corrosion products could effectively reduce the rate of Volmer reaction and hydrogen adsorption process, and accelerate the process of hydrogen atom desorption, thus leading to the remarkable decrease in C 0. [ABSTRACT FROM AUTHOR]

Hydrogen transport by blending hydrogen into natural gas transmission pipelines and by pure-hydrogen pipelines is a prospective mode of energy transmission during the transition to renewables. The risk of hydrogen embrittlement (HE) in pipeline steels must first be quantified to ensure safe pipeline operation. This review provides an overview of HE in pipeline steels. Most pipeline steels have reduced ductility when exposed to hydrogen partial pressures of 100 bar and above. Higher-strength pipeline steels (X80 and X100) have been found to undergo HE at ∼50 bar hydrogen. Hydrogen-induced subcritical crack growth in pipeline steels has not been reported in the literature. There are few articles on HE in pipeline welds, with some indications that the weld is more susceptible to HE, and some indications that it is less. The relationship between hydrogen pressure and absorbed hydrogen concentration has not been evaluated. Gaps in knowledge are identified in the conclusions. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen isotope permeation through structural materials is a key issue for developing nuclear fusion energy, which will cause fuel loss and radioactive pollution. Developing ceramic coatings with high thermal shock and hydrogen resistance is an effective strategy to solve this issue. In this work, a layer-structured Cr/Cr x N coating was successfully fabricated by a facile electroplating-based nitridation technique, which is easy, facile, and applicable to coating complex-shaped substrates. The Cr/Cr x N coating, composed of a bottom Fe/Cr interdiffusion zone, a middle Cr layer, and a top Cr x N layer, exhibits high bonding strength, high anti-thermal-shock ability, and high deuterium permeation resistance. Its bonding strength achieves 43.6 MPa. The Cr/Cr x N coating remains intact even after suffering 300 thermal shock cycles under a 600 °C-water condition. Through optimizing the nitridation temperature, the Cr/Cr x N coating achieves a deuterium permeation reduction factor (PRF) as high as 3599 at 500 °C. Considering its scalable fabrication technique and considerable properties, the developed Cr/Cr x N coating may serve as a novel high-performance hydrogen permeation barrier in various fields.

The effect of Mo content of 1400 MPa-grade high-strength bolt steel on hydrogen diffusion behavior and the hydrogen evolution reaction were studied using a hydrogen permeation experiment, potentiodynamic polarization tests, thermal desorption spectroscopy, and the first-principle calculation. Two 1400 MPa-grade high-strength bolt steels with different Mo content were used. Based on the potentiodynamic polarization tests, both steels' electrochemical behavior was similar in the test range. The hydrogen permeation experiment showed that the process of hydrogen adsorption and absorption was significantly promoted, and hydrogen desorption and recombination were slightly promoted, with the Mo content increasing from 0.70 to 1.09 wt%. The thermal desorption spectroscopy showed the overall reaction of hydrogen permeation and evolution. The increasing Mo content facilitated hydrogen entry behavior and increased the hydrogen content. According to the first-principle calculation and the density functional theory, this phenomenon is induced by the stronger bonding ability of Mo-H than Fe-H. This work could guide the design of 1400 MPa-grade high-strength bolt steel. [ABSTRACT FROM AUTHOR]

In this study, an electrochemical hydrogen permeation experiment was used to determine the diffusion parameters, and a hydrogen microprint test was used to visualize the distribution of hydrogen in X65 pipeline steel with different levels of cold deformation. The hydrogen permeation curves show that both hydrogen permeation current density and effective hydrogen diffusion coefficient decrease with increasing cold deformation. The density of reversible and irreversible hydrogen traps is calculated from the permeation parameters, and it is found that the amount of both traps increases with increasing deformation, especially a significant increase in reversible hydrogen traps, which is in agreement with the results measured by thermal desorption spectroscopy. Hydrogen microprint test results indicate that the degree of hydrogen aggregation on the specimen surface increases with increasing cold deformation, especially at phase and grain boundaries. In addition, the dislocation configuration after cold deformation was further investigated by transmission electron microscopy. [ABSTRACT FROM AUTHOR]

This work investigates the effect of a constant load on hydrogen diffusion through a Q&P steel containing metastable retained austenite by combining electrochemical hydrogen permeation and thermal desorption spectroscopy. Material samples are placed under different external loading conditions, ranging from 50% to 125% of the yield stress. The permeation transients indicate that hydrogen diffusion is delayed under all stressed conditions, even at stresses in the elastic regime, with the delay increasing with the applied load. From thermal desorption spectroscopy performed on the same specimens after the permeation test, it appears that the samples tested under load show a high temperature peak, which is not present in the unloaded sample. Further differential scanning calorimetry analysis confirms that the high temperature peak is related to retained austenite and is a result of hydrogen effusion and hydrogen release due to transformation of the retained austenite. • Hydrogen is not trapped at retained austenite during regular charging. • Constant load during permeation causes slower hydrogen diffusivity. • Thermal desorption reveals trapping at austenite during permeation at constant load. • Desorption temperature is correlated to austenite decomposition with DSC and XRD. [ABSTRACT FROM AUTHOR]

Hydrogen embrittlement is a serious threat to the safety operation for hydrogen blended natural gas pipelines. To determine the critical safety hydrogen blending ratio, in-situ high-pressure gaseous hydrogen permeation tests and slow strain rate tensile tests of X80 pipeline steel were conducted in the simulated hydrogen blended natural gas environments with 0–20 vol% hydrogen. The permeability characteristics, mechanical properties and fracture morphologies were systematically analyzed, and the embrittlement mechanism was discussed. Results show that the subsurface hydrogen concentration, ductility loss and hydrogen embrittlement susceptibility increased significantly as hydrogen blending ratio increased from 10% to 15%. Moreover, a positive correlation between subsurface hydrogen concentration and hydrogen embrittlement index was revealed. Combining the gaseous hydrogen permeation, SSRT results and fracture analysis, the 10% hydrogen blending ratio was determined as the conservative critical value for the safety operation of X80 hydrogen blended natural gas pipelines. • Permeation parameters of X80 steel are obtained through gaseous H 2 permeation tests. • HE susceptibility of X80 steel with different hydrogen blending ratios is analyzed. • An approximate linear relationship between C 0 and F H is established. • 10% is determined as the conservative critical safety hydrogen blending ratio. [ABSTRACT FROM AUTHOR]

The corrosion of spring steel is very important for vehicle safety. In this work, we conducted an experiment on multi-element micro-alloy composition design; the corrosion resistance of a 60Si2Mn spring was improved by adding Cr, Ni, Cu and other corrosion-resistant elements, and the corrosion resistance index (I) was increased from 3.21 to 8.62. Hydrogen embrittlement resistance was studied using a hydrogen permeation experiment and a slow strain rate tensile experiment. For this study, the following steps were performed: Firstly, the material composition was designed, and the experimental materials that met the experimental design were prepared according to the corresponding deformation and heat treatment process; secondly, the experimental materials were charged with hydrogen; and finally, conventional tensile testing, slow tensile testing and fracture morphology testing were carried out. A hydrogen permeation experiment was carried out for the materials. The result showed that, with the increase of hydrogen charging time, the hydrogen content of two steel samples increased, and the plasticity indexes such as elongation and reduction of the area appeared in three different stages which rapidly decreased, slowly declined, and then tended to balance. The uniform NbC nano precipitated phase can double the number of irreversible hydrogen traps (Nir) per unit volume, and decreased the effective hydrogen diffusion coefficient (Deff) from 1.135 × 10−10 to 6.036 × 10−11. It limited the free diffusion of hydrogen and made the immersed hydrogen harmless, thus improving the hydrogen embrittlement resistance of corrosion-resistant spring steel 60Si2Mn. [ABSTRACT FROM AUTHOR]

The permeation of hydrogen gas was studied in meta-aluminous (tectosilicate) glass powders of Li2O⋅Al2O3⋅SiO2 (LAS), Na2O⋅Al2O3⋅SiO2 (NAS) and MgO⋅Al2O3⋅SiO2 (MAS) systems by pressure loading and vacuum extraction in the temperatures range 210-310 °C. With this method, both the solubility S and the diffusivity D were determined, while the permeability was given by the product SD. For all glasses, S was found to decrease with temperature, while D increased. Since the activation energy of diffusion of H2 molecules exceeded that of dissolution, permeation increased slightly with temperature. When extrapolated to standard conditions (25 °C), the permeability of tectosilicate glasses was found to be only 10-22-10-24 mol H2 (m s Pa)-1, which is 8-10 magnitudes lower than most polymers. Thin glass liners of these compositions are expected to be the most effective barrier for tanks of pressurised hydrogen. [ABSTRACT FROM AUTHOR]

The inhibitory effect of La3+ on the hydrogen permeation of X70 pipeline steel was investigated via steady-state hydrogen permeation current (i∞) through electrochemical hydrogen permeation tests. The experimental permeation data were fitted with a constant concentration model and Electrochemical Impedance Spectroscopy (EIS) tests were conducted to characterize the activity of Hydrogen Evolution Reaction (HER) after the optimization of electrochemically active surface area. Additionally, the kinetics of HER and the adsorption/desorption process is calculated by Iyer-Pickering-Zamanzadeh (IPZ) and surface effect models, of which the results demonstrate that the La3+ in the corrosion products could effectively reduce the rate of Volmer reaction and hydrogen adsorption process, and accelerate the process of hydrogen atom desorption, thus leading to the remarkable decrease in C0.

The hydrogen permeation behavior of QP1180 high strength steel for automobile was studied in simulate coastal atmosphere environment by using Devanathan-Stachurski dual electrolytic cell, the cyclic corrosion test (CCT), thermal desorption spectrometry (TDS) and electrochemical measurement methods. The current density of hydrogen permeation generally increases with reducing the relative humidity from 95% to 50% and periodically changes in the CCT process. These mainly result from the evolution of corrosion and rust layer on the specimen surface with the atmospheric humidity and intermittent salt spraying. The contents of diffusible hydrogen and non-diffusible hydrogen in the steel enlarge slightly in the CCT process. The plastic deformation about 11.3% results in much higher diffusible hydrogen content in steel, but noticeably reduces the hydrogen permeation current and almost has no influence on the non-diffusible hydrogen content. The combination of double electrolytic cell and standard cyclic corrosion test can effectively characterize the hydrogen permeation of high strength steel in atmospheric service environments.