The hydrogen crisis for metals: hydrogen embrittlement

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Those working in industries related to hydrogen should be aware that hydrogen embrittlement poses a significant challenge to industrial applications; if it occurs without being detected, the consequences can be disastrous! Today, I’ll give you a brief overview of hydrogen embrittlement and the related countermeasures. 1. Concept of hydrogen embrittlement: Hydrogen embrittlement occurs when metal materials experience a decrease in their mechanical properties as a result of absorbing hydrogen atoms, particularly a reduction in ductility and an increase in brittleness. Hydrogen atoms are very small and can penetrate solid metals. Once absorbed by the metal, hydrogen reduces the stress required for cracks to initiate and propagate within the metal, thereby leading to embrittlement. Hydrogen embrittlement occurs most significantly in steel, as well as in iron, nickel, titanium, cobalt and their alloys; copper, aluminum and stainless steel are less prone to hydrogen embrittlement. Generally, materials with higher strength are more susceptible to hydrogen embrittlement. . Hydrogen embrittlement generally does not occur at room temperature; most metals develop hydrogen embrittlement at temperatures above 150°C, with the effect being more pronounced at temperatures above 300°C. 2. Mechanism of hydrogen embrittlement Hydrogen embrittlement is a complex process that mainly involves the following factors: 1) Internal pressure: At high hydrogen concentrations, the absorbed hydrogen recombines in the voids to form hydrogen molecules, generating pressure within the metal and causing cracks to form; this is known as hydrogen cracking. If bubbles form on the surface, it is referred to as hydrogen blistering. 2) Hydrogen-enhanced local plasticity: Hydrogen increases crack dislocation movement, leading to increased local plastic deformation. 3) Hydrogen facilitates separation: Hydrogen atoms reduce the bonding force between metal atoms. 4) Hydrogen adsorption-induced dislocation emission: Hydrogen atoms adsorb on the dislocation lines, reducing the energy barrier for dislocation movement and promoting dislocation emission. 5) Hydrogen-enhanced strain-induced vacancies: Hydrogen interacts with strain-induced vacancies to form hydrogen-vacancy complexes, affecting the plastic deformation of the material. 6) Hydride formation: Certain metals have a strong affinity for hydrogen; in areas with stress concentration, supersaturated hydrogen may combine with metal atoms to form hydrides, and these brittle phase structures can lead to fracture. 7) Influence of environmental factors: The hydrogen embrittlement phenomenon is also affected by environmental factors such as temperature and stress. 8) Hydrogen trapping effect: Hydrogen atoms become concentrated at certain trapped sites within the material, forming hydrogen traps. 3. Hydrogen embrittlement characteristics of common metal materials: Hydrogen embrittlement is a common phenomenon in metal materials, and the hydrogen embrittlement characteristics and influencing factors vary among different materials. These mainly include: steel materials, aluminum alloys, titanium alloys, magnesium alloys, high-strength fasteners, and industrial pipes. For those working in the hydrogen industry, the hydrogen embrittlement problem associated with industrial pipes arises because hydrogen enters the metal in atomic form and then recombines into molecules within the metal, generating high pressure; in severe cases, this can lead to bulging or wrinkling of the surface. 4. Methods for preventing hydrogen embrittlement. Hydrogen embrittlement cannot be prevented during use; it can only be controlled at the source. The following are some common measures to prevent hydrogen embrittlement: 1) Minimize the pickling time and add corrosion inhibitors to reduce hydrogen production. 2) Select high-strength, high-toughness materials and ensure their cleanliness. 3) Reduce the stress on the materials used and avoid stress concentration. 4) Use surface treatment methods that do not produce hydrogen, such as mechanical zinc plating, Dacromet, and Kumite. 5) Bolts and nuts with electro-galvanized coatings should be subjected to baking for hydrogen removal promptly after electroplating. In summary, the phenomenon of hydrogen embrittlement requires us to adopt a proper attitude to better address this challenge and ensure the long-term stability and safety of metal materials. With the advancement of technology, we have reason to believe that hydrogen embrittlement, this old and complex problem, will be managed and resolved more effectively.