Hydrogen embrittlement issue

Hydrogen embrittlement can also be considered a type of corrosion. Broadly speaking, metal corrosion refers to the physico-chemical interactions between metals and environmental media; as a result, the properties of the metals change, and this can lead to damage to the metals, the environment, or the functions of the systems in which they are part of. Hydrogen embrittlement: Under high temperature and pressure, molecular hydrogen is partially broken down into atomic hydrogen; or in a wet acidic corrosive environment, hydrogen atoms are generated through electrochemical reactions. Once these hydrogen atoms penetrate into the steel, they reduce the bonding force between the steel’s grains, resulting in a decrease in the steel’s elongation and reduction ratio, as well as changes in its strength. This phenomenon is known as hydrogen embrittlement. Hydrogen embrittlement is a type of embrittlement that is reversible ； After the hydrogen is released through heat treatment, the metal will regain its original mechanical properties. Factors affecting hydrogen embrittlement include: 1) Hydrogen partial pressure. The higher the hydrogen partial pressure, the shorter the delayed failure time ； 2) Temperature: Hydrogen embrittlement does not occur at high temperatures; at such levels it has transformed into hydrogen corrosion. It does not occur either when the temperature is too low, because hydrogen lacks the activity to penetrate deeply into the metal lattice at such times. It generally occurs in the temperature range of -30°C to 30°C ； 3) The strength of metal materials; the higher the strength, the greater the likelihood of hydrogen embrittlement ； 4) The index of hydrogen embrittlement in the metal’s microstructure, such as martensitic structure, is 3 times that of spheroidally pearlitic structure ； 5) Stress level: The brittle fracture of materials occurs under sufficient stress; by reducing the stress level below the energy required for lattice slip, hydrogen embrittlement will not occur. Engineering measures to prevent hydrogen embrittlement include: avoiding use in its temperature-sensitive areas ； Choose materials with low strength ； Reduce the stress levels of metal components.

This post was last edited by JFTANG726 on 2009-10-16 09:57. Once hydrogen embrittlement occurs, it cannot be eliminated. Hydrogen embrittlement occurs when hydrogen dissolved in steel aggregates into hydrogen molecules, causing stress concentration that exceeds the steel’s strength limit and resulting in the formation of tiny cracks within the steel. Also known as white spots. Hydrogen embrittlement can only be prevented, not cured. At normal temperature and pressure, hydrogen does not cause significant corrosion in steel; however, when the temperature exceeds 300°C and the pressure is above 30 MPa, hydrogen embrittlement occurs as a form of corrosion damage, especially under high-temperature conditions. Such as the desulfurization tower, shift tower, and ammonia synthesis tower in the ammonia synthesis production process ； Some hydrogenation reaction units in the refining process ； Methanol synthesis towers in the petrochemical production process, etc.

Measures to prevent hydrogen embrittlement: 1) Reduce hydrogen content； 2) Increase the solubility of hydrogen in metals or alloys ； 3) Ensure the operating environment ； 4) Select the appropriate heat treatment process to eliminate residual stresses ； 5) Others, such as surface coatings, anodization, and hydrogen-absorbing media. The above is all reproduced content

I found some good introductory articles online, so I’m posting them here all at once! What is \"hydrogen embrittlement\"? How to prevent it? Hydrogen embrittlement (or hydrogen damage) in pressure vessels refers to the erosion of their walls by hydrogen, which leads to a reduction in the material’s plasticity and strength, thereby causing cracking or delayed brittle failure. The damage caused by high-temperature and high-pressure hydrogen to steel is mainly due to hydrogen penetrating into the metal in atomic form and then recombining into molecules inside the metal, generating high pressure; in severe cases, this can lead to bulging or wrinkling of the surface ； Hydrogen combines with carbon in steel, causing decarburization of the steel, or reducing the sulfides and oxides present in it. The hydrogen that causes hydrogen embrittlement failure in pressure vessels can be present originally in the equipment; for example, moisture present during steelmaking and welding processes is reduced to produce hydrogen at high temperatures, which then dissolves in the liquid metal. Or, during electroplating or pickling, the hydrogen atoms adsorbed on the steel surface become supersaturated, allowing hydrogen to penetrate into the steel ； It can also be absorbed into the medium after use; for example, in petroleum and chemical containers, there are many mediums that contain hydrogen or impurities such as hydrogen sulfide. The characteristics of hydrogen embrittlement in steel are mainly manifested in the microstructure. On its corroded surface, decarburized ferrite of steel can often be seen, and the hydrogen embrittlement layer features corrosion cracks that extend along the grain boundaries. In containers with particularly severe corrosion, bulges caused by hydrogen embrittlement can be observed macroscopically. Whether a container containing hydrogen (or hydrogen sulfide) in a medium will suffer from hydrogen embrittlement depends mainly on the operating temperature, the partial pressure of hydrogen, the exposure time, and the chemical composition of the steel. The higher the temperature and the greater the hydrogen partial pressure, the deeper the hydrogen embrittlement layer in carbon steel, and the shorter the time it takes for hydrogen embrittlement to cause failure; among these factors, temperature is particularly important. The higher the carbon content in steel, the greater its tendency to hydrogen embrittlement under the same temperature and pressure conditions. Adding elements such as chromium, titanium, and vanadium to steel can prevent the occurrence of hydrogen embrittlement.