The issue of hydrogen embrittlement

Hydrogen corrosion should be considered above 200°C, while hydrogen embrittlement should be considered below 200°C.

Mechanism of hydrogen embrittlement: Hydrogen atoms have the smallest atomic radius among all atoms, and they can easily dissolve and diffuse in steel; the higher the temperature, the greater the solubility of hydrogen in steel. Hydrogen atoms are generally found in the gaps between metal atoms, accumulating near dislocations (local areas in the lattice where atoms are misaligned). When steel is subjected to external forces, the stress distribution within the material is uneven; stress concentration occurs in areas of discontinuity within the material, as well as at internal defects and microcracks. Under the influence of the stress gradient, hydrogen atoms move along with the dislocations toward these stress-concentrated areas, weakening the bonds between iron atoms in those regions. As a result, cracks arise and propagate in these high-hydrogen areas ； Furthermore, there are many microcracks in the crystal; when hydrogen accumulates at these cracks, it adsorbs on their surfaces, reducing the surface energy. As a result, the cracks tend to expand, leading to brittle fracture. According to the mechanism of hydrogen embrittlement, the likelihood of hydrogen embrittlement occurring at high temperatures and low pressures is low. Since the hydrogenation reactor operates at high temperatures, steel inevitably absorbs some hydrogen. When the reactor is shut down and the temperature drops, the solubility of hydrogen decreases. If the cooling rate is too fast and the temperature falls below 200°C, some of the hydrogen does not have time to diffuse out and remains trapped within the steel, resulting in hydrogen embrittlement of the steel. When driving again, the tensile stress generated under pressure may cause hydrogen embrittlement fracture of the equipment. Therefore, although hydrogenation reactors are not pressure vessels covered by the Fixed and Mobile Pressure Vessels Regulations, regular inspection and testing are still required over time to prevent hydrogen embrittlement. ,

My reaction temperature is above 200, and the pressure is relatively low. Could you tell me something about hydrogen corrosion? I need to prepare a description so that my supervisor can find an institution to conduct tests

That’s right, no one is coming to do the inspections, so I want to check it out! But didn’t someone say above that hydrogen corrosion occurs easily? I don’t know which one is more likely to occur. Only if it can be clearly specified will the management pay attention to it; otherwise, there will be no oversight! Thank you

Metallography? I’m hearing this for the first time! But it seems that other reaction vessels are also used only to measure thickness; I’ll check

In simple terms, hydrogen combines with carbon in steel to form methane, which then explodes inside or on the surface of the steel.

Hydrogen embrittlement occurs when hydrogen enters the crystal structure and occupies the positions of atoms, thereby reducing the strength of the steel. This condition can be eliminated through annealing treatment, and it is reversible.

There is such a risk, but since the equipment isn’t considered a pressure vessel, is it still required to undergo regular inspections?