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.

In our previous work, we found that hydrogen permeation can be noticeably reduced during Ni–Cu electroplating by the addition of Ce salt to the plating solution. The mechanism of hydrogen permeation inhibition via Ce salt was further studied in the present work. Through the Iver–Pickering–Zamenzadeh (IPZ) model fitting of the kinetic of hydrogen evolution reaction, we found that the trace Ce salt that precipitated during electroplating could improve Tafel reaction kinetic parameters and reduce the strength of the Ni–H and Cu–H bonds due to its abundant d/f electrons and enough d/f orbitals. Meanwhile, Ce can provide electrons for the Heyrovsky reaction. These effects promoted surface electron migration and thus led to the desorption of adsorbed hydrogen atoms (Hads) and the decreased diffusion of Hads into the Ni–Cu coatings. The accuracy of the IPZ model fitting results was verified by hydrogen evolution rate experiments during the electroplating process. Hence, Ce salt can effectively inhibit hydrogen permeation and reduce the dehydrogenation annealing time, thereby showing great potential for energy saving and emission reduction in the electroplating industry.

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 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 behavior the surface of X70 pipeline steel in alkaline environment after applying low tensile stress was investigated by electrochemical tests. It is found by hydrogen permeation tests that the steady-state hydrogen permeation current density (i∞) and sub-surface hydrogen concentration (C0) greatly increased, whereas apparent diffusivity (D) was almost unchanged after applying low tensile stress. LSV and EIS measurements indicated that the activity of hydrogen evolution reaction (HER) was improved by elastic tensile stress. The mechanism of stress enhanced the hydrogen embrittlement sensitivity was conducted by Iyer-Pickering-Zamanzadeh (IPZ) and surface effect model. The results demonstrated that the Volmer reaction was facilitated, and the Tafel reaction was restricted by the application of tensile stress. The activation energy obtained by the Arrhenius equation indicated that when the specimen suffered from tensile stress, the adsorption activation energy decreased, and the desorption activation energy increased, leading to the remarkable increase of C0.

Cerium is a rare‐earth element that is often utilized as a corrosion inhibitor to improve the corrosion resistance of materials. However, it is rarely used in electrodeposition. Herein, Ce‐modified Ni–Cu coatings are prepared using a pulse current (PC) electrodeposition technique. This modification of Ni–Cu coatings with Ce is investigated via scanning electron microscopy, cyclic voltammetry, potentiodynamic polarization, and Mott–Schottky measurements. It is demonstrated in the results that Ce modification alters the reduction potential of Cu, causing an underpotential deposition effect, which is beneficial for Cu electrodeposition. In addition, Ce accumulates close to the coating/passive film interface and gives rise to a “site‐blocking” effect, which reduces the transmission rate of cation and oxygen ion vacancies. Finally, Ce accumulation noticeably decreases the concentration of point defects and enhances the corrosion resistance of Ni–Cu coatings.

High-strength steel parts are electroplated with corrosion-resistant coatings and then subjected to hydrogen removal annealing to prevent hydrogen embrittlement. This approach has become the standard in the industry. However, it is not beneficial to energy conservation and emission reduction. Herein, a rare earth salt (Ce salt) additive is determined to be efficient for inhibiting hydrogen permeation during electroplating process. A modified Devanathan-Stachurski method was applied to investigate the hydrogen permeation behavior. Results demonstrated that the hydrogen permeation during direct current (DC) and pulsed current (PC) electrodeposition was considerably inhibited by the Ce salt additive. The amount of permeated hydrogen increased in the following order: PC electrodeposition with Ce electrodeposition. Therefore, the environmentally friendly additive has great potential for energy saving and emission reduction in the electrodeposition or pickling industry.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Addition of trace lanthanum salt in acid solution was found to be enhanced inhibitory effect on hydrogen permeation to X70 pipeline steel. The hydrogen permeation curves were performed to show that the addition of La 3+ inhibits hydrogen permeation by accelerating the recombination of the adsorbed hydrogen atoms and the desorption of hydrogen molecule, which decrease the subsurface hydrogen concentration. The inhibitory effect of La 3+ involves the film formation process. Moreover, electrochemical impedance spectroscopy analysis (EIS) depict that the inhibitive effect is caused by the catalysis of the recombination-desorption-evolution of adsorbed hydrogen atoms by La(OH) 3 /La 2 O 3 . This provides a novel solution for the prevention of hydrogen-induced cracking of high-strength steel, which often causes catastrophic accidents.

The effect of stress on the cathodic hydrogen evolution behavior of X70 pipeline steel was investigated by electrochemical tests, tensile tests, and microstructural characterization. The results indicated that the tensile stress enhanced the activity of hydrogen adsorption sites on the metal surface, which was considered as the dominating factor affecting gen-eration, adsorption, and permeation of hydrogen atoms. The subsurface hydrogen atom concentrations quantified by Cyclic voltammetry (CV) tests and the data calculated by hydrogen permeation experiments showed a good correspondence. The results indicated that the tensile stress enhanced the adsorption of hydrogen atoms on the surface and an inhibitory effect on the Tafel and Heyrovsky reaction, thereby leading to the increase of the subsurface hydrogen atom concentration, enhance the hydrogen embrittlement suscep-tibility of the X70 steel material as demonstrated by plasticity loss in the tensile tests.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Ni-Cu coatings were obtained through direct current electrodeposition in electroplating bath with ceric sulfate in varying concentration (0-1.2 g/L), respectively. Effects of ceric sulfate on microstructure and corrosion resistance of the coatings were analyzed through high-resolution transmission electron microscopy, potentiodynamic polarization, and localized electrochemical impedance spectroscopy. Semiconductor performance of a passive film formed on the Ni-Cu coatings was characterized by the Mott-Schottky measurements. Results demonstrated that Ce was co-deposited in the Ni-Cu coating obtained in the ceric sulfate containing electroplating bath. The trace addition of Ce distinctly improved corrosion resistance of the Ni-Cu coatings, which is ascribed to that the interfacial reactions between Ni-Cu coating and the passive film were suppressed by the reduction of the point defect diffusivity after the formation of a dense cerium oxide film. (c) 2021 The Authors. Published by Elsevier B.V. on behalf of Institute of Metal Research, Chinese Academy of Sciences. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

综述了氢渗透的研究方法和研究历史,总结了当前对氢损伤机理的研究,以及在易发生氢脆环境下的氢渗透行为规律和影响氢行为的因素.在这些研究的基础上,国内外先后开发了许多氢渗透防护技术,如:阻碍氢原子渗入基体,在材料表面制备涂镀层;消除钢中有害元素的方式,改变中氢原子陷阱的数目;从组织入手,开发高纯度、高抗氢钢,包括一些系列铁素体合金钢等.综述了从传统的电沉积阻氢合金镀层,到新工艺制备阻氢陶瓷层的发展.阻氢涂层具有阻氢性能极佳,兼具保护作用的优点,但容易失效,破损后会加快基体的局部腐蚀;而通过冶金、热处理来净化钢材,改变组织成分开发的纯净钢,其实际抗氢脆性能并不理想,仍然会出现氢引起的力学性能下降,并且具有控制工艺复杂、能耗大的缺点.由此认为,氢一旦进入金属材料内部,造成材料的性能损伤不可避免,防止氢进入金属材料是该领域的关键科学问题.氢渗透过程是氢损伤发生的关键步骤,那么阻碍氢渗透过程的进行就成了氢损伤防护措施的重中之重.抑制氢渗透过程的发生需要从降低氢原子浓度梯度、降低材料内部氢陷阱密度和结合能两方面入手,开发有效的抑氢手段,抑制氢渗透过程,使材料内部的氢原子浓度小于临界氢原子浓度.