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Alternating current (AC) corrosion is a type of corrosion that occurs in buried pipelines under AC stray current interference, which can increase the hydrogen embrittlement sensitivity of pipelines. However, rare research works have been conducted on the hydrogen permeability characteristics of pipeline steel under AC stray current interference. The purpose of this paper is to study hydrogen permeation behavior of X80 steel under AC stray current interference.

In this paper, the hydrogen permeation behavior of X80 steel under AC interference is studied by AC hydrogen charging experiment in a dual electrolytic cell. The relationship between hydrogen evolution rate and hydrogen permeation flux is studied using the gas collection method. The difference between AC hydrogen permeability and direct current (DC) hydrogen permeability is also discussed.

The anodic dissolution caused by AC corrosion promotes the chemical desorption reaction of the adsorbed hydrogen atoms on the surface, reducing the hydrogen atom absorption ratio by 70%. When the AC is smaller than 150░ A/m², the hydrogen permeation process is controlled by the hydrogen atom generation rate, and the hydrogen permeation flux increases with the increase in hydrogen atom generation rate. When the AC exceeds 400░ A/m², the hydrogen permeation process is controlled by the absorption ratio. The hydrogen permeation flux decreases with the decrease in the absorption ratio. Under AC interference, there is a maximum hydrogen permeation flux that linearly correlates to the H⁺ concentration in the solutions.

The high-strength steel is very sensitive to hydrogen embrittlement, and X80 steel has been widely used in oil and gas pipelines. To date, no research has been conducted on the hydrogen permeation behavior of pipeline steel under AC interference, and the hydrogen permeability characteristics of pipeline steel under AC interference are not clear. The research results of this paper are of great significance for ensuring the intrinsic safety of high-strength pipelines under AC stray current interference.

The purpose of this study is to develop a model extending Oriani’s formula by introducing a normalised concentration to simulate hydrogen diffusion in a multi-material system such as coated steels, under the presence of traps.

Implemented through the finite element method based on the analogy between mass diffusion and heat transfer, the governing equation was applied to investigate the combined effects of hydrogen traps and surface oxide films on hydrogen permeation in ferritic steels.

This study shows that the effective diffusivity varies over several orders of magnitude depending on the traps and films. This explains the divergence of measured hydrogen diffusivities in steels. It is revealed that hydrogen permeation in steels with Pd or Ni film is a trapping-dominant transport process, while hydrogen permeation in steel with oxide film is a process controlled by both trapping effect and retarding effect of oxide film. The oxide film enhances total hydrogen concentration within the steel substrate and is therefore detrimental. The Pd or Ni film has a little influence on total hydrogen concentration distribution depending on trapping energy.

Hydrogen flux curves and transient hydrogen concentration distributions can be directly obtained through the developed model. The proposed approach can also be extended to investigate other interstitial (i.e. carbon, oxygen and nitrogen) diffusion with traps revisited in complex systems.

This paper aims to study the mechanism of hydrogen embrittlement in 12Cr2Mo1R(H) steel, which will help to provide valuable information for the subsequent hydrogen embrittlement research of this kind of steel, so as to optimize the processing technology and take more appropriate measures to prevent hydrogen damage.

The hydrogen diffusion coefficient of 12Cr2Mo1R(H) steel was measured by the hydrogen permeation technique of double electrolytic cells. Moreover, the influence of hydrogen traps in the material and experimental temperature on hydrogen diffusion behavior was discussed. The first-principles calculations based on density functional theory were used to study the occupancy of H atoms in the bcc-Fe cell, the diffusion path and the interaction with vacancy defects.

The results revealed that the logarithm of the hydrogen diffusion coefficient of the material has a linear relationship with the reciprocal of temperature and the activation energy of hydrogen atom diffusion in 12Cr2Mo1R(H) steel is 23.47 kJ/mol. H atoms stably exist in the nearly octahedral interstices in the crystal cell with vacancies. In addition, the solution of Cr/Mo alloy atom does not change the lowest energy path of H atom, but increases the diffusion activation energy of hydrogen atom, thus hindering the diffusion of hydrogen atom. Cr/Mo and vacancy have a synergistic effect on inhibiting the diffusion of H atoms in α-Fe.

This article combines experiments with first-principles calculations to explore the diffusion behavior of hydrogen in 12Cr2Mo1R(H) steel from the macroscopic and microscopic perspectives, which will help to establish a calculation model with complex defects in the future.

This paper aims to study the effect of temperature on the process and kinetic parameters of the hydrogen evolution reaction of X80 under cathodic protection (CP) in 3.5% NaCl solution.

Potentiodynamic polarization combined with the hydrogen permeation test is used to analyze the hydrogen evolution reaction (HER) process and the rate-determining step for which is diagnosed through the electrochemical impedance spectrum method. Then, the influence of temperature on kinetic parameters of HER can be known from the results obtained by using the Iver-Pickering-Zamenzadeh model for data analysis.

The results show that the HER proceeds through Volmer–Tafel route with the Volmer reaction acting as the rate-controlling step; Increasing temperature gives a higher activity of the HER on X80, it also accelerates the hydrogen desorption and diffusion of hydrogen into the metal.

There exist few studies on the topic of how temperature affects the HER process. It is imperative to conduct a relevant study to give some instruction in cathodic protection system design and this paper fulfills this need.

The purpose of this study is to investigate the effects of the cementite morphology on the hydrogen trapping behavior in low-alloy pipeline steel.

In this study, the hydrogen trapping behavior in low-alloy pipeline steel was quantitatively studied by a combination of microstructural observations, electrochemical hydrogen permeation experiments and thermal desorption spectroscopy (TDS) analyses.

P-1 and P-2 steels are two samples with different microstructures. The morphology of cementite precipitates in the P-1 and P-2 steels was different. Lamellar cementite is present in P-2 steel and only granular cementite in P-1 steel, which led to a better irreversible hydrogen trapping ability of P-2 steel, which was confirmed by subsequent hydrogen permeation and TDS experiments.

The study of these deep hydrogen trap sites is helpful in improving the hydrogen embrittlement resistance of low-alloy pipeline steels.

The influence of 4‐amino‐5‐mercapto‐3 n‐propyl‐1‐2‐4‐triazole (AMPT) on corrosion and hydrogen permeation through mild steel in 0.5M H₂SO₄ and 1M HCl has been studied using weight loss measurements and various electrochemical techniques. AMPT is found to be more inhibitive in H₂SO₄ than in HCl. Potentiodynamic polarisation studies clearly prove the fact that this compound behaves as a mixed inhibitor; but predominantly as a cathodic inhibitor. Hydrogen permeation studies and AC impedance measurements also indicate an improved performance of the compound in H₂SO₄. The adsorption of this compound on the mild steel surface obeys Temkin’s adsorption isotherm.

A few nitrones such as N‐benzilidene aniline‐N‐oxide, N‐(O‐hydroxy benzilidene) aniline‐N‐oxide (HN) and N‐(α‐naphthylidene) aniline‐N‐oxide (NN) have been synthesised and investigated for evaluating their efficiency as inhibitors for the corrosion of mild steel in 1M HCl at different concentrations of nitrones ranging from 0.025‐1.0mM and at different temperatures ranging from 30‐70°C. Among these compounds NN gives the best performance even at higher temperatures. Potentiodynamic polarisation studies reveal the fact that all compounds behave as mixed type inhibitors. Hydrogen permeation studies reveal the fact that all the compounds bring down the permeation current. The absorption of these compounds on the mild steel surface from 1M HCl obeys Temkin’s absorption isotherm.

This paper aims to use an imidazole-based n-ionic Gemini surfactant derived from palm oil to inhibit the sulfide stress corrosion cracking of a supermartensitic stainless steel.

The slow strain rate testing technique, hydrogen permeation tests and potentiodynamic polarization curves have been used.

Addition of the inhibitor below the critical micelle concentration (CMC) decreased the corrosion current density (i_corr), but not enough to avoid embrittlement due to the entry of hydrogen into the steel. Instead, the addition of the inhibitor close to the CMC decreased the i_corr, suppressed the entry of hydrogen and inhibited the sulfide stress cracking of steel. Finally, the addition of inhibitor above the CMC led to a slight increase of i_corr and promoted localized corrosion, however, the sulfide stress cracking of steel was inhibited.

A green sulfide stress corrosion cracking inhibitor of a supermartensitic stainless steel has been obtained.

The influence of N‐heterocyclics, viz. imidazole (IA), benzimidazole (BIA) and 2‐methyl imidazole (MIA) on the corrosion and hydrogen permeation through mild steel in 1 N H₂SO₄ and in 1N HC1 has been studied using weight loss and various corrosion monitoring techniques. Imidazole and benzimidazole inhibit the corrosion of mild steel in both the acidic solutions, but methyl imidazole accelerates the corrosion. They behave as cathodic inhibitors by influencing the cathodic polarization reaction. Except methyl imidazole, the other two compounds reduce the hydrogen permeation current in both the acids. The adsorption of these compounds on the mild steel surface from both the acids obeys Temkin’s adsorption isotherm. Trends in the increase of charge transfer resistance and decrease of capacitance values also show the adsorption of inhibitors on the metal surface.

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.

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.

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.

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.