Electrochemical Hydrogen Permeation Tests Research Articles

Manipulating nano-WS2 aggregates in electroplated Ni coating to mitigate hydrogen embrittlement in X70 pipeline steel

WS2 is a two-dimensional nanomaterial with significant potential for hydrogen barrier applications. Herein, WS2/Ni composite coatings were fabricated on X70 pipeline steel substrates via electrodeposition. The properties of the composite coatings were systematically examined by electrochemical hydrogen permeation tests, hydrogen evolution kinetics tests, SSRT, SKPFM, and FEM. The results indicate that varying the deposition time leads to changes in coating microstructure, which correspondingly influence hydrogen permeation performance. Furthermore, the hydrogen barrier mechanism of the WS2/Ni composite coatings involves two key processes: the inhibition of hydrogen evolution reactions on the coating surface and hydrogen adsorption by WS2 within the coating interior.

Optimizing hydrogen permeation properties of WS2-Ni composite coatings on pipeline steel for improved hydrogen protection

Tungsten disulfide (WS2) has broad applications due to its unique molecular structure and outstanding physicochemical properties. In particular, the physical barrier properties of WS2 make it suitable to act as barriers against hydrogen. Herein, WS2-Ni composite coatings are prepared by electrodeposition to mitigate hydrogen-induced damage of X70 pipeline steel. The influence of the WS2 concentration on the hydrogen resistance of coating is assessed by electrochemical hydrogen permeation test, hydrogen adsorption simulation, slow strain rate tensile test (SSRT), and fracture analysis. As the WS2 concentration increases, the distributions of WS2 in the coatings transition from sparse to uniform and then agglomeration, while the grain size of Ni decreases initially and then decreases. These microstructural changes impact the hydrogen adsorption sites and diffusion paths, leading to a non-linear relationship between the hydrogen permeation resistance and WS2 concentration. This similar concentration dependence is also observed from the hydrogen embrittlement (HE) resistance of coatings, suggesting that enhancing the hydrogen permeation resistance can improve the HE resistance. This study highlights the great potential of WS2 as an effective barrier against hydrogen permeation, and the results provide insights into the hydrogen protection mechanism of pipeline steel.

Mechanism of local hydrogen entry into Fe sheets induced by atmospheric corrosion: Significance of potential, pH, and rust layer thickness

Local hydrogen entry under a NaCl droplet on Fe sheets was analysed by employing a hydrogenochromic sensor and electrochemical hydrogen permeation tests. Large crystallographic pits barely promoted hydrogen entry, because crystallographic pitting proceeded at potentials higher than the potential of the hydrogen evolution reaction. Hydrogen entry was accelerated because of acidification under an island-like rust layer. The rust layer became thick in its outer regions, mainly owing to severe corrosion and alkalisation around the rust-formed area. Hydrogen entry was prominent under the thick rust layer after disappearance of the droplet, owing to the high concentrations of chloride ions and protons.

Optimizing the hydrogen embrittlement resistance by Cu addition in a low carbon high strength steel

This study used the electrochemical hydrogen permeation test and the slow strain rate tensile (SSRT) test to examine the impact of Cu addition on hydrogen embrittlement (HE) in a low carbon high strength steel. The following method explains how Cu alloying affected HE resistance. (i) Cu alloying refined the prior austenite grain size, which increased the effective area of grain/packet/block/lath boundaries and mitigated the strain localization, and thus provided additional reversible hydrogen traps, homogenized the hydrogen distribution and suppressed local accumulation of hydrogen at boundaries. (ii) Cu alloying promoted the Cu-rich precipitates, which had strong binding energy with hydrogen. Also, the “incoherent” fcc Cu-rich precipitates contrary to the “slightly coherent” Cu-rich with an energy-poor trap strongly trapped hydrogen and enhanced the HE resistance.

A novel strategy for estimating the diffusion behavior of hydrogen in metallic materials with the combined effect of stress corrosion and hydrogenation: Case study of 2.25Cr-1Mo-0.25V high-strength steel

Hydrogen equipment for long-term service in complex hydrogen environment is threatened by the phenomenon of hydrogen-induced damage, and the combined effect of stress corrosion and hydrogen attack can intensify the formation and development of hydrogen damage. In this study, a new strategy to indirectly estimate the hydrogen diffusivity of metallic materials under tensile stress was proposed by combining the electrochemical hydrogen permeation test (EHPT), the hydrogen diffusion descriptive equation based on Fick's law, and hydrogen pre-charged tensile test. The results revealed that the hydrogen permeation curve obtained after considering the effect of the residual hydrogen extraction stage was highly approximate to the theoretical trend. The hydrogen embrittlement (HE) susceptibility of the pre-tensioned tensile and hydrogen-charged specimens increased with increasing stress. At tensile stress (0–400 MPa) the effective hydrogen diffusivity of 2.25Cr-1Mo-0.25 V steel was: Deff=1.1686+0.4842×exp(σ/277.869). The micrograph from the fracture surfaces also reflected the aggravated brittle fracture characteristics of the steel.

Methodology of the electrochemical hydrogen permeation test: A parametric evaluation

In this study, a methodological approach is pursued to gain an elaborated understanding concerning the Devanathan-Stachurski technique. Different experimental test parameters such as the polarization potential at the exit side, the applied charging current density, the electrolyte, the oxygen content, the sample roughness and the electrolyte composition, are modified to evaluate their influence. It is found that the surface roughness and possible contaminations from of the electrolyte are of high importance for realizing a stable entrance surface state. Furthermore, the partial transient procedure can be used for determining a diffusion coefficient which approaches the lattice diffusion coefficient.

Hydrogen permeation and hydrogen damage behavior of high strength casing steel in acidic environment

To explore the effect of hydrogen permeation on pipes in an acidic environment, the tensile mechanical properties of three types of high strength steels were evaluated before and after hydrogen filling. The hydrogen damage behavior of three kinds of high-strength steels was studied by electrochemical hydrogen permeation test, MTS tensile test, and fracture morphology analysis. First, the basic physical and chemical properties of the materials were analyzed, and then the D-S double electrolytic cell technology was used for hydrogen permeation experiment. Finally, the influence of hydrogen loading on the tensile mechanical properties of the steel was determined by MTS tensile test and fracture morphology analysis. As the hydrogen filling current increases, the system temperature rises and the pH decreases, the hydrogen diffusion coefficient increases and the sensitivity of the steel to hydrogen embrittlement increases. The higher the steel strength, the higher the hydrogen diffusion coefficient, the higher the diffusible hydrogen concentration, the higher the hydrogen embrittlement sensitivity. The hydrogen damage evaluation method of high-strength steel used in this paper can provide a reference for the applicability evaluation of oil well pipe under acidic environment and provide theoretical guidance for the selection of oil well pipe in the field.

The mechanism of inhibitive effect on hydrogen permeation of X70 steel by lanthanum microalloying: Enhanced kinetics of desorption

In this work, electrochemical hydrogen permeation tests were carried out to obtain the steady-state hydrogen permeation current of X70 pipeline steel in acid environment and alkaline electrolyte with applied cathodic overpotentials simulating the service conditions of pipelines. It is shown that La-microalloying can efficiently reduce the steady-state hydrogen permeation current density while maintaining the same mechanical performance. The experimental permeation data were fitted with Iyer-Pickering-Zamanzadeh (IPZ) and surface effect model to analyze the inhibitive mechanism on hydrogen permeation, and the results depicted that La element on the material surface greatly facilitates the desorption process of hydrogen atoms. In addition, the calculated hydrogen diffusion coefficient was found smaller after La microalloyed, which can be ascribed to the larger hydrogen trap density. It is suggested that La-microalloying can mitigate hydrogen damage of X70 pipeline steel in both acidic environment or under cathodic protection.

Effects of Applied Cathodic Current on Hydrogen Infusion, Embrittlement, and Corrosion-Induced Hydrogen Embrittlement Behaviors of Ultra-High Strength Steel for Automotive Applications

The effects of the electrogalvanizing conditions (a combination of plating current and time) on hydrogen infusion, embrittlement, and corrosion-induced hydrogen embrittlement (HE) behaviors of ultra-high strength steel were examined. A range of experimental and analytical methods, including electrochemical impedance spectroscopy, hydrogen permeation, polarization, and slow strain rate test, were employed. The results showed that the applied cathodic current density during electrogalvanizing had an inverse relationship with the Zn crystalline size. A smaller cathodic current density and longer plating time led to a larger crystalline size, resulting in a higher infusion rate of hydrogen atoms, and HE-sensitivity (i.e., mechanical degradation with larger density of secondary crack in fracture surface). On the other hand, a larger cathodic current density and shorter plating time caused a higher anodic dissolution rate and smaller polarization resistance of the coating when exposed to neutral aqueous environments. Hence, a higher rate of galvanic corrosion between the coating and exposed steel substrate (e.g., locally damaged areas around coating layer) resulted in a higher infusion rate of hydrogen atoms and HE-sensitivity. This study provides insight into the desirable plating conditions for electro-Zn plating on ultra-high strength steels with enhanced resistance to hydrogen infusion and embrittlement, induced by aqueous corrosion.

Response of hydrogen diffusion and hydrogen embrittlement to Cu addition in low carbon low alloy steel

Hydrogen embrittlement (HE) has arisen as a critical issue for the development of high strength steel. The austenite and Cu-rich precipitates can provide stable trapping sites for diffusible hydrogen, and thus improved the resistance to HE. But the research on the synergistic effect of Cu and austenite on HE in low carbon low alloy steel has not been actively reported. In this study, four steels with varying Cu addition (0-3 wt%) were fabricated, and their resistance to HE was evaluated. The role of Cu addition was investigated by the ductile-brittle transition temperature (DBTT) value obtained from Charpy impact test and the loss of elongation measured from slow-strain-rate tensile (SSRT) test after hydrogen charging. Also, the hydrogen diffusivity and concentration were evaluated by electrochemical hydrogen permeation test. Cu addition resulted in a first decrease and subsequent increase of effective diffusion coefficient (D eff ), elongation loss and DBTT, and the minimum value was achieved in steel with 1.5 wt% Cu addition, indicating a higher resistance to HE. The unraveled mechanism was that Cu addition increased the content of retained austenite, which impeded the diffusion of hydrogen during deformation. But the stability of retained austenite decreased when the content of retained austenite reached a high value, which led to martensitic transformation and accordingly increased HE susceptibility. Moreover, Cu addition promoted the formation of Cu-rich precipitates in which Cu cluster/bcc Cu-rich precipitate coherent/semi-coherent with matrix can be strong trapping sites for hydrogen, and fcc Cu-rich precipitate acted as weak trapping sites for hydrogen. In addition, a higher density of dislocations was found in the steel with 1.5 wt% Cu addition, which may contribute to lower D eff and higher density of hydrogen traps (N T ). The present work suggested that Cu addition can enhance the resistance to HE during tensile and impact processes for the design of high strength steel. • Cu addition resulted in a first decrease and subsequent increase in the effective diffusion coefficient (D eff ) of hydrogen. • Cu addition increased the elongation rate and decreased the ductile-brittle transition temperature (DBTT) of the steels after hydrogen embrittlement. • The resistance to hydrogen embrittlement during tensile and impact process was determined by retained austenite, Cu-rich precipitates and dislocations in the microstructure. • The resistance to hydrogen embrittlement varied with the content and stability of austenite and the structure of Cu-rich precipitates.

Effects of La3+ on the hydrogen permeation and evolution kinetics in X70 pipeline steel

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.

Hydrogen diffusion kinetics in dual-phase (DP 980) steel: The role of pre-strain and tensile stress

The current study investigates the influence of pre-strain (un-strained, 3 %, and 6 % engineering strain) and in-situ tensile stress (50 %, 110 %, and 125 % of the yield stress (YS)) on the hydrogen diffusion and trapping behaviour in DP 980 steel. Electrochemical hydrogen permeation tests were conducted using a custom-built Devanathan-Stachurski (DS) cell integrated with a horizontal tensometer. The results showed that the value of apparent diffusion coefficient (Dapp) decreased from 5.4 ± 0.1 to 3.8 ± 0.029 × 10−7 cm2 s−1, while trap density (NT) and sub-surface hydrogen concentration (Capp) increased from 1.08 ± 0.01 to 1.58 ± 0.012 × 1021 cm−3, 2.70 ± 0.13 to 3.27 ± 0.10 × 10−4 mol H cm−3, respectively for unstrained and 6 % pre-strain conditions. This is due to increased dislocation density in ferrite and martensite. Hydrogen permeation tests under tensile stress (in-situ) revealed that the applied elastic stress of 50 % of YS showed a slight increase in Dapp and a decrease in NT values. This is due to an increase in the interstitial space between the atoms at applied elastic load favouring hydrogen diffusion. The plastic tensile stress of 110 % of YS showed the highest value of steady-state permeation current density iss (169 ± 10.6 µA cm−2). It could be due to an expanded lattice of martensite accommodating more hydrogen because of its elastic deformation. The tensile stress of 125 % of YS results in a significant reduction in Dapp (2.86 × 10−7 cm2 s−1) and an increase in Capp (5.52 × 10−4 mol H cm−3) and NT (2.11 × 1021 cm−3) as a result of plastic deformation in ferrite and martensite. The decay transient studies revealed that the applied elastic tensile stress enhances the rate of desorption of diffusible hydrogen, increasing lattice diffusion coefficient DL. The plastic pre-strain and plastic tensile stress resulted in slower desorption, lower DL, and an increase in reversible trap density.

Effect of cold deformation before heat treatment on the hydrogen embrittlement sensitivity of high-strength steel for marine risers

Herein, the effects of cold deformation before heat treatment on the hydrogen diffusion and hydrogen embrittlement sensitivity of low-alloy high-strength steel for marine risers were investigated. The influence of cold deformation on hydrogen diffusion and hydrogen embrittlement was elucidated by electrochemical hydrogen permeation test and slow strain rate tension test. A tempered martensitic structure was gradually refined by increasing the cold deformation amount. This phenomenon increased the density of hydrogen traps in the steel sample, decreasing the hydrogen effective diffusion coefficient and prolonging the hydrogen penetration time. Due to the high deformation, the hydrogen embrittlement sensitivity index of the tempered martensite decreased significantly and the brittle fracture characteristics of slow strain rate tensile fracture were insignificant. The ability of the microstructure to resist hydrogen embrittlement failure was effectively enhanced. In addition, the refinement of the martensitic structure increased the number and homogeneity of hydrogen traps in the tested steel, thereby enhancing the hydrogen solubility of the microstructure. The hydrogen content at the hydrogen traps could not attain to the critical value, inhibiting the initiation and propagation of hydrogen embrittlement cracks.

Preparation and properties of Al2O3/SiO2 composite tritium permeation barrier and its effects on the inner walls of pipelines

A tritium permeation barrier can be prepared on the surface of structural materials to effectively inhibit tritium penetration and leakage. In this study, an Al2O3/SiO2 composite tritium permeation barrier was prepared on the inner wall of a 316L stainless steel tube via the slurry method. The microstructure and phase composition of the coatings were investigated by using SEM, XRD, TEM, and XPS. The thermal shock resistance and hydrogen resistance of the coating were studied. Results show that the coating is continuous and dense, and is composed of Al2O3 and amorphous SiO2. The thickness of the coating is approximately 80 μm and well attaches to the substrate. Compared with thermal shock at 700 °C, the coating exhibits better thermal shock resistance at 500 °C and 600 °C. The Al2O3/SiO2 composite coating has good phase stability after thermal shock. Electrochemical hydrogen permeation tests demonstrate that the Al2O3/SiO2 composite coating effectively improves the hydrogen resistance of the 316L stainless steel substrate.

Effect of Mo and Nb on mechanical properties and hydrogen embrittlement of hot-rolled medium-Mn steels

The effects of Mo and Nb on the mechanical properties and hydrogen embrittlement (HE) of hot-rolled medium-Mn steel were investigated. The diffusion behavior of hydrogen was examined using an electrochemical hydrogen permeation test. The mechanical properties and HE were studied using a slow strain rate test. The results show that most Mo and Nb served as solid-solution atoms in the hot-rolled steels, and little carbide content was observed. Both Mo and Nb increased the volume fraction of retained austenite (VA), decreased the starting temperature of martensitic transformation (MS), and retarded the martensite transformation. The effect of Nb was more pronounced. Simultaneous addition of Mo and Nb had a synergistic effect on increasing VA, decreasing MS, and retarding martensite transformation. The elongation of the samples increased with an increase in VA. The strength exhibited the opposite trend. A small amount of Nb (0.04 wt%) significantly improved the HE resistance of steels to a much greater extent than Mo (1 wt%). Filmy retained austenite formed along the primary austenite grain boundaries because of the Nb addition; it inhibited hydrogen-induced cracks, leading to better HE resistance. Blocky retained austenite, formed by the simultaneous addition of Mo and Nb, deteriorated the HE resistance.

Hydrogen Isotope Permeation Behavior of AlCrFeTiNb, AlCrMoNbZr and AlCrFeMoTi High-Entropy Alloys Coatings

The hydrogen permeation behavior of novel AlCrFeTiNb, AlCrMoNbZr and AlCrFeMoTi high-entropy alloy (HEA) coatings were investigated. The hydrogen permeability of HEA coatings prepared by magnetron sputtering technology were tested using gas-driven deuterium permeation and electrochemical hydrogen permeation methods. The gas-driven permeation results show that the deuterium permeation resistance of the AlCrFeTiNb coating is the worst because of the unstable structure at a high temperature. Scanning electron microscope (SEM) and X-ray Diffraction (XRD) analysis proved a loose surface morphology of the AlCrFeTiNb coating and demonstrated the formation of iron-based oxides after deuterium permeation experiments. A high content of iron in HEA coating is disadvantageous for improving the hydrogen permeability. Differently, electrochemical hydrogen permeation reveals that the AlCrMoNbZr coating could resist hydrogen permeation better in a corrosive environment (0.2 mol/L KOH solution). The AlCrFeMoTi coating was peeled off after an electrochemical hydrogen permeation test due to the poor corrosion resistance. The hydrogen behavior of HEA coatings was discussed in detail. Our study provides a promising thought on hydrogen permeation of HEA coatings.

Influence of tempering time on the fracture toughness of hydrogen pre-charged 42CrMo4 steel

This work aims to find suitable 42CrMo4 steel grades for working in energetic applications dealing with high pressure hydrogen gas. Consequently, the influence of the tempering time on the hydrogen embrittlement (HE) sensitivity of 42CrMo4 steel quenched and tempered at 600 °C is studied. Compact tension (CT) specimens were pre-charged with gaseous hydrogen in a pressurized reactor at 19.5 MPa and 450 °C for 21 h and tested for fracture toughness afterwards in air. The hydrogen concentration introduced in the steels was determined using thermal desorption analysis (TDA). The fracture micromechanisms were subsequently identified by means of scanning electron microscopy (SEM). Electrochemical hydrogen permeation (EHP) tests were also performed to gain better insight into the interaction between hydrogen atoms and the microstructure of these steel grades, and consequently to justify the results. The fracture toughness of hydrogenated 42CrMo4 steel increases considerably with the tempering time, being this behaviour correlated with the density of hydrogen traps in the steel. Brittle fracture micromechanisms, associated with the hydrogen-enhanced decohesion mechanism HEDE (martensitic lath decohesion and intergranular fracture) were present to a lesser or greater degree in all the tempering times.

Hydrogen Diffusivity in Different Microstructures of 42CrMo4 Steel

It is well known that the presence of hydrogen decreases the mechanical properties of ferritic steels, giving rise to the phenomenon known as hydrogen embrittlement (HE). The sensitivity to HE increases with the strength of the steel due to the increase of its microstructural defects (hydrogen traps), which eventually increase hydrogen solubility and decrease hydrogen diffusivity in the steel. The aim of this work is to study hydrogen diffusivity in a 42CrMo4 steel submitted to different heat treatments—annealing, normalizing and quench and tempering—to obtain different microstructures, with a broad range of hardness levels. Electrochemical hydrogen permeation tests were performed in a modified Devanathan and Stachursky double-cell. The build-up transient methodology allowed the determination of the apparent hydrogen diffusion coefficient, Dapp, and assessment of its evolution during the progressive filling of the microstructural hydrogen traps. Consequently, the lattice hydrogen diffusion coefficient, DL, was determined. Optical and scanning electron microscopy (SEM) were employed to examine the steel microstructures in order to understand their interaction with hydrogen atoms. In general, the results show that the permeation parameters are strongly related to the steel hardness, being less affected by the type of microstructure.

MXene Coatings: Novel Hydrogen Permeation Barriers for Pipe Steels.

MXenes are a new class of two-dimensional (2D) materials with promising applications in many fields because of their layered structure and unique performance. In particular, the physical barrier properties of two-dimensional nanosheets make them suitable as barriers against hydrogen. Herein, MXene coatings were prepared on pipe steel by a simple spin-coating process with a colloidal suspension. The hydrogen resistance was evaluated by electrochemical hydrogen permeation tests and slow strain rate tests, and the corrosion resistance was assessed by potentiodynamic polarization. The results reveal that MXene coatings offer excellent hydrogen resistance and corrosion protection by forming a barrier against diffusion. Experimentally, the hydrogen permeability of the MXene coating is one third of the substrate, and the diffusion coefficient decreases as well. The mechanistic study indicates that the hydrogen resistance of the MXene coatings is affected by the number of spin-coated layers, while the concentration of the d-MXene colloidal suspension determines the thickness of a single coating. However, damage to the sample surface caused by the colloidal suspension that contains H+ and F− may limit the improvement of the hydrogen resistance. This paper reveals a new application of 2D MXene materials as a novel efficient barrier against hydrogen permeation and the subsequent alleviation of hydrogen embrittlement in the steel substrate.

Hydrogen Permeation Property of Bulk Cementite

This study investigated the hydrogen permeation property of cementite by fabricating bulk cementite sample using the process combining the mechanical ball milling and subsequent pulse current sintering. The bulk cementite sample having a 96 vol% of cementite was successfully fabricated. The prepared bulk cementite showed no signal of hydrogen permeation during the 3.5 day of electrochemical hydrogen permeation test. The morphology of blister formed in the sample indicated that diffusion coefficient of hydrogen in cementite is very small.