Hydrogen corrosion, hydrogen blistering, hydrogen embrittlement, and hydrogen erosion of refinery equipment

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. Hydrogen corrosion, hydrogen embrittlement, and hydrogen attack in refinery equipment 1. Hydrogen embrittlement Definition: Hydrogen atoms diffuse into the interior of the metal (mostly through the vessel walls), where they combine to form hydrogen molecules that then escape. If hydrogen atoms diffuse into the pores in steel and combine there to form hydrogen molecules, and since these hydrogen molecules cannot diffuse, they accumulate and create high internal pressures, leading to bulging or even cracking of the steel surface—a phenomenon known as hydrogen embrittlement. Low-strength steels, especially those containing a large amount of non-metallic inclusions, are most prone to hydrogen blistering. Corrosion environments that cause hydrogen blistering: The medium usually contains toxins such as hydrogen sulfide, arsenic compounds, cyanides, or phosphorus ions. These media prevent the hydrogen evolution reaction. Preventive measures: Eliminate toxic agents ； If it cannot be eliminated, use a calm steel with fewer pores, or an austenitic stainless steel with low hydrogen permeability. Or use nickel lining, rubber-lined lining, plastic protective layer, fiberglass lining, etc ； Sometimes a corrosion inhibitor is added. The density of a body-centered cubic lattice is 0.68 (meaning that 68% of the lattice’s volume is occupied by atoms, with the remainder being voids), and its coordination number is 8 (the higher the coordination number, the tighter the arrangement of atoms and the smaller the voids) ； The density of the face-centered cubic lattice and the hexagonal close-packed lattice is 0.74, with a coordination number of 12. 2. Hydrogen embrittlement Definition: In high-strength steels, the metal lattice is highly deformed; when hydrogen atoms enter the metal, they increase the strain in the lattice, thereby reducing toughness and ductility and causing embrittlement. This phenomenon is known as hydrogen embrittlement. Hydrogen embrittlement is not related to voids in the steel, so relying solely on the use of killed steel is ineffective. Preventive measures: Use materials that are not sensitive to hydrogen embrittlement, such as alloy steels containing Ni and Mo. During the manufacturing process, try to avoid or minimize the generation of hydrogen. 3. Hydrogen embrittlement Definition: Under high temperature and pressure conditions, hydrogen enters the metal and reacts chemically with a certain component or element, resulting in the degradation of the metal; this phenomenon is known as hydrogen embrittlement. At temperatures above 200°C, hydrogen enters low-strength steel and reacts with carbides to produce methane gas. This gas occupies a large volume, causing small cracks and voids within the metal, which in turn makes the steel brittle and prone to breaking under even slight deformation. This kind of rupture occurs without any warning and is extremely dangerous. Preventive measures: Use hydrogen-resistant steel. Options include 16MnR (HIC), 15CrMoR (equivalent to 1Cr-0.5Mo), 14Cr1MoR (equivalent to 1.25Cr-0.5Mo), 2Cr-0.5Mo, 2.25Cr-1Mo, 2.25Cr-1Mo-0.25V, 3Cr-1Mo-0.25V, etc. Cr and Mo in hydrogen-resistant steel can form stable carbides, thereby reducing the chances of hydrogen combining with carbon and preventing the formation of methane gas. In theory, hydrogen corrosion is divided into three types, but in practice, all three types of corrosion occur almost simultaneously. Therefore, for equipment operating in environments subject to hydrogen corrosion (hydrogen-rich environments), material selection is generally carried out based on the Nelson curve, and great attention must be paid to this. Hydrogen-resistant materials are metal materials that can resist hydrogen-induced damage or hydrogen embrittlement. Hydrogen damage refers to the damage that occurs in metals or alloys under tensile stress due to the presence of excess hydrogen. Its manifestations mainly include hydrogen-induced plasticity loss, high-temperature hydrogen corrosion, hydrogen-induced irreversible damage (white spots, hydrogen bubbles, hydrogen-induced cracks, etc.), and hydrogen-induced delayed fracture. Hydrogen embrittlement refers to the phenomenon of material becoming brittle under the influence of internal hydrogen or ambient hydrogen. Common hydrogen-resistant materials include austenitic stainless steels, precipitation-hardened austenitic alloys, low-alloy steels, aluminum alloys, and copper alloys. The main characteristic of hydrogen-resistant materials is that alloys with a face-centered cubic structure exhibit better hydrogen resistance compared to those with a body-centered cubic structure ； Anti-hydrogen alloys are sensitive to hydrogen only within a certain temperature range ； The hydrogen resistance of an alloy is related to its grain size and strain rate; the finer the grains, the better the hydrogen resistance, and as the strain rate increases, the tendency to hydrogen embrittlement decreases. Anti-hydrogen materials can be used as structural materials under high-pressure hydrogen conditions (715 MPa), as well as as lining materials for hydrogenation reactors and in the manufacture of hydrogen storage pressure vessels.