Papers by Keyword: Hydrogen Permeation

Abstract: The main objective of this work was to obtain information about the hydrogen diffusion behaviour in a cold-worked austenitic stainless steel (X3CrMnNiMoN17-8-4) in which deformation-induced martensite formation occurs during mechanical deformation. Three different states of pre-deformation (31 %, 39 % and 49 %) that showed induced phase transformation from austenite to α’martensite as well as the solution-annealed material were part of this study. All samples were charged with hydrogen in a 0.1 M NaOH solution. This charging took place electrolytic with 10 mA cm^-2 at three different temperatures (50 °C; 65 °C and 80 °C) in the double cell according to Devanathan and Stachurski. Due to the very slow diffusion of hydrogen through austenite, the samples were not charged until the equilibrium state was reached. To find out the necessary diffusion parameters, the data were fitted with numerical optimisation. Using this method, the effective diffusion coefficients of charging could be determined for all material states. The study also contains microscopic analyses to visualize the effect of cold working on the microstructure of the material. The appearance of α’-martensite significantly contributes to the susceptibility to hydrogen uptake leading to increasing diffusion coefficients in relation to higher pre-deformation.

Abstract: The pipeline steels which are used for transportation of natural gas and crude oil suffer from hydrogen damage at their internal as well as external surfaces. The internal surfaces of pipelines are generally affected due to hydrogen induced cracking and the external surfaces due to the soil environmental conditions which cause stress corrosion cracking. In the present investigation, the electrochemical corrosion behavior of X70 pipeline steel was studied in sour environment and near neutral soil environment. To assess the mechanism of hydrogen damage in steel, electrochemical hydrogen charging and permeation techniques were used to characterize the hydrogen distribution, trapping and its diffusion in X70 pipeline steel. It has been found that corrosion behavior of pipeline steel in the sour environment is higher than the near neutral soil solution. From the hydrogen permeation study it is established that the hydrogen permeation rate increases with the square root of the charging current density, and the increase of hydrogen flux is directly proportional to the subsurface hydrogen concentration.

Abstract: A series of accelerated degradation experiments at high temperatures have been performed for Pd-coated V-10 mol% Fe alloy membranes in order to investigate the degradation behavior of hydrogen permeability. The degradation of the membrane becomes severer with increasing testing temperature. The temperature dependence of the 20% degradation rate almost obeys the Arrhenius relationship, suggesting that the degradation phenomenon occurs by a kind of thermal activation process. It is found that the addition of a small amount of W into Pd overlayer improves the durability of the membrane significantly.

Abstract: Using a substrate of AISI 316L austenitic stainless steel, which is used for components in high-pressure hydrogen systems, the hydrogen barrier properties of samples with single-layer coatings of TiC, TiN, and TiAlN as well as a multi-layered coating of TiAlN and TiMoN were evaluated. The ion plating method was used, and coating thicknesses of 2.0–2.6 μm were obtained. Hydrogen permeation tests were carried out under a differential hydrogen pressure of 400 kPa and at a temperature between 573 and 773 K, and the quantities of hydrogen that permeated the samples were measured. This study aimed at elucidating the relationship between the microstructures of the coatings and the hydrogen permeation properties. Coatings of TiC, TiN, TiAlN, and TiAlN/TiMoN facilitated reductions of the hydrogen permeabilities to 1/100 or less of that of the uncoated substrate. The samples coated with TiN and TiC that developed columnar crystals vertical to the substrate exhibited higher hydrogen permeabilities. The experiment confirmed that the coatings composed of fine crystal grains were highly effective as hydrogen barriers, and that this barrier property became even more efficient if multiple layers of the coatings were applied. The crystal grain boundaries of the coating and interfaces of each film in a multi-layered coating may serve as hydrogen trapping sites. We speculate that fine crystal structures with multiple crystal grain boundaries and multi-layered coating interfaces will contribute to the development of hydrogen barriers.

Abstract: A novel methodology based on electrochemical hydrogen permeation tests is proposed to study the efficiency of commercial inhibitors for industrial acid pickling of iron and mild steels. Weight loss measurements and hydrogen permeation tests have been carried out in order to compare the sensitivity of different techniques to variations of low inhibitor dosages. It has been found a close dependence between low amounts of filming inhibitors and hydrogen uptake in the metallic surface with related permeation currents. The high sensitivity of permeation currents may be very useful to establish and also control the optimum amount of active substances in industrial pickling baths, with related cost savings. The implementation of the proposed methodology to improve the control of industrial pickling plants is also envisaged, since it would be possible to improve both sensitivity and time response of experimental permeation curves.

Abstract: The effect of CO₂ on the hydrogen permeation behaviour of carbon steel was investigated in a high temperature and high pressure hydrogen permeation device, through hydrogen permeation test, weight loss test, hydrogen content test, and SEM-EDS. The results showed that the peak value of the hydrogen permeation curves were almost the same with or without CO₂, but the hydrogen permeation curve rose sharply, and then decreased gradually to a stabilized current value in H₂S/CO₂ environment, which was lower than in H₂S environment. The corrosion rates and the amount of hydrogen of steel in H₂S/CO₂ environment were lower than in H₂S environment. Therefore, it is considered that CO₂ has an effect on the hydrogen permeation in H₂S, mainly due to the change of corrosion products.

Abstract: Effect of hydrogen on metals is a complex phenomenon. The objective of this paper was to outline the recent application of scanning Kelvin probe (SKP) for a deeper understanding of nature and properties of metal-hydride system. SKP belongs to the family of scanning probe electrochemistry techniques (SPETs) that are currently used and developed. Different applications of SKP technique for hydrogen detection in metals, hydrogen permeation through metals with high local resolution, and quantitative analysis of hydrogen in materials, were presented. The emphasis in this work was on presenting specific applications of SKP rather than extensive reviews; details of how and why this technique is useful in research area was given.

Abstract: The presented paper is devoted to the study of hydrogen diffusion characteristics in the C-Mn-Si TRIP 800 steel. The steel was tested in three different states: in as-received state after hot and cold rolling and subsequent heat treatment; and furthermore after 5% and 10% tensile deformation. Hydrogen diffusion characteristics were studied by means of electrochemical permeation method. Two build up transients corresponding to lower and higher charging current densities as well as a decay transient were recorded during experiment. The lowest values of hydrogen diffusion coefficient (from 1 to 3.5.10^-7 cm².s^-1) were observed during the first build up transient; the value of 3.5.10^-7 cm².s^-1 corresponded to 10% tensile deformation. During the 2^nd build up transient corresponding to the higher charging current density, hydrogen diffusion coefficients increased markedly reflecting thus the fact that hydrogen trapping was less pronounced. For decay transients hydrogen diffusion coefficients were situated between values obtained for the 1^st and 2^nd build up transients. In all studied states, a rather high sub-surface hydrogen concentration was observed during the 1^st build up transient rising to 12.6 ppm of hydrogen in as-received state. The obtained results are explained taking into account steel microstructure and hydrogen trapping.

Abstract: This study aims to develop novel experimental procedure that quantifies response of AHSSs with different microstructures, deformation status, and strength levels to hydrogen. The capacity for trapped hydrogen, kinetics of hydrogen absorption and loss, and hydrogen mobility are measured and analyzed by permeation tests. The experimental findings are discussed in terms of microstructural features for an interstitial free (IF) and a dual phase (DP) steels. Further, the density of trap sites and its effect on effective diffusivity of hydrogen in the steel are analyzed by means of a diffusion model.

Abstract: In order to enhance the hydrogen permeation, Silicon carbide (SiC) was prepared with CeO₂-NiO mixed oxides via sol-gel process and the SiC membranes with various contents of χ wt% mixed oxides (χ = 20, 40, 60 and 80) were fabricated by hot-press sintering (HPS) at 1173 K under vacuum condition. The effect of the CeO₂-NiO mixed oxides was studied in terms of properties on hydrogen permeation. All the membranes were characterized by XRD, FE-SEM and BET instrument. The hydrogen permeation test was carried out at various temperatures under 0.1 MPa. Hydrogen permeation flux of the 80 wt% CeO₂-NiO/SiC membrane, which has the highest value, was obtained at 2.92×10^-6 mol/m²sPa, 323 K. The reaction enthalpy (ΔH°) was calculated as - 4.95 J/mol by Arrhenius’s plot.