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.

Анализ водородоустойчивости алюминиевых сплавов

It was established by the methods of quantum chemistry that tungsten W and rhenium Re are the most effective additives that increase the hydrogen resistance of aluminum Al. It is shown that W and Re strongly compress aluminum, but at the same time have a rather large covalent radius. In addition, each W and Re atom form stable chemical bonds with 12 Al atoms. As a result, the W and Re atoms strongly bind Al atoms significantly increasing the energy of vacancy formation and slowing down the process of hydrogen embrittlement. All basic physical and mechanical properties of the most hydrogen-resistant aluminum compound WReAl24 have been calculated using density functional theory.

Study on Hydrogen Resistance of X42 Pipeline Steel Under Electrochemical Hydrogen Charging Condition

With the development of renewable energy, hydrogen energy is paid more and more attention. Hydrogen is an excellent energy carrier, but it is difficult to store and transport because of its special properties. Hydrogen blended with nature gas is considered to be one of best transition solutions to solve the problem of large-scale hydrogen transportation. But hydrogen embrittlement occurs when the pipeline steel used to transport natural gas is exposed to hydrogen environment. Referencing to ASME B31.12, X42 pipeline steel is selected as the research object in this paper. And the mechanical properties of X42 were tested by electrochemical hydrogen charging, slow strain rate tensile (SSRT) test and fatigue crack growth (FCG) test combined with thermal desorption spectroscopy (TDS) and SEM. Hydrogen adsorption properties of X42 pipeline steel at room temperature was measured by TDS. SSRT test showed that the strength of X42 strengthened slightly in electrochemical hydrogen charging environment, but the plasticity decreased significantly, and the embrittlement degree of materials increased with the elevated current density. FCG test showed that the presence of hydrogen will accelerate the crack growth rate and reduce the fatigue life of materials. SEM images of tensile and fatigue specimens showed that hydrogen transforms the fracture mode from ductile fracture to cleavage fracture.