What is hydrogen embrittlement?

Hydrogen embrittlement of a pressure vessel means that its wall is eroded by hydrogen, resulting in a reduction in the material's plasticity and strength, which may lead to cracking or delayed brittle failure. The damage caused by hydrogen at high temperature and high pressure to steel is mainly because hydrogen penetrates into the metal in an atomic state and recombines into molecules inside the metal, generating high pressure. In severe cases, it can cause bulges or wrinkles on the surface. ； Hydrogen combines with the carbon in the steel to decarburize the steel or reduce the sulfides and oxides in the steel. The hydrogen that causes hydrogen embrittlement damage of pressure vessels can be originally present in the equipment. For example, moisture during steelmaking and welding processes is reduced at high temperatures to generate hydrogen, which is dissolved in the liquid metal. Or when the equipment is electroplated or pickled, the steel surface is supersaturated with adsorbed hydrogen atoms, causing hydrogen to penetrate into the steel. ； It can also be absorbed from the medium after use. For example, in petroleum and chemical containers, there are many impurities containing hydrogen or hydrogen sulfide in the medium. The characteristics of hydrogen embrittlement in steel are mainly manifested in the microstructure. Decarburized ferrite of steel can often be seen on its corrosion surface, and the hydrogen embrittlement layer has corrosion cracks extending along the grain boundaries. For containers that are particularly corroded, bulges caused by hydrogen embrittlement can be seen macroscopically. Whether a container containing hydrogen (or hydrogen sulfide) in the medium will suffer from hydrogen embrittlement mainly depends on the operating temperature, partial pressure of hydrogen, action time and chemical composition of the steel. The higher the temperature and the more severe the hydrogen partial pressure, the deeper the hydrogen embrittlement layer of carbon steel and the shorter the time for hydrogen embrittlement rupture to occur. Temperature is especially an important factor. The higher the carbon content of the steel, the more serious the tendency of hydrogen embrittlement will be under the same temperature and pressure conditions. Elements such as chromium, titanium, and vanadium are added to steel to prevent hydrogen embrittlement.

Hydrogen embrittlement is a phenomenon of destruction of metal materials caused by the combined action of hydrogen and stress. It causes the material to suddenly break and cause serious accidents.

For alloy steel, a phenomenon in which the metal turns green due to the entry of hydrogen into the crystal structure. Its damage to the alloy is fatal! ! It's devastating! !

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1. Hydrogen embrittlement is hydrogen dissolved in steel that aggregates into hydrogen molecules, causing stress concentration that exceeds the strength limit of the steel and forms small cracks inside the steel. Also called white spots. 2. Internal hydrogen embrittlement. Trace amounts of hydrogen (on the order of 10-6) that enter the interior of the steel during the smelting process of materials and the manufacturing and assembly processes of parts (such as electroplating and welding) cause the material to embrittle or even crack under the action of internal residual or external stress. When cracking has not yet occurred, the properties of the steel can be restored through dehydrogenation treatment (for example, heating to above 200°C for several hours to reduce the internal hydrogen). Internal hydrogen embrittlement is therefore reversible. 　　3. Heat treatment is not suitable for you. 　　The method of heat treatment is to heat the workpiece to a certain temperature, keep it warm for a period of time, and slowly cool it so that the hydrogen gradually becomes smaller and precipitates out as the solubility increases. 　　Heating will destroy the coating. 　　4. How to prevent and treat it. 　　In your case, the main reason is poor pickling control. 　　First, try to shorten the pickling time as much as possible ； Secondly, add corrosion inhibitor to reduce hydrogen production. 　　Hydrogen embrittlement (or hydrogen damage) of a pressure vessel means that its wall is eroded by hydrogen, resulting in a reduction in the plasticity and strength of the material, which may lead to cracking or delayed brittle failure. The damage caused by hydrogen at high temperature and high pressure to steel is mainly because hydrogen penetrates into the metal in an atomic state and recombines into molecules inside the metal, generating high pressure. In severe cases, it can cause bulges or wrinkles on the surface. ； Hydrogen combines with the carbon in the steel to decarburize the steel or reduce the sulfides and oxides in the steel. The hydrogen that causes hydrogen embrittlement damage of pressure vessels can be originally present in the equipment. For example, moisture during steelmaking and welding processes is reduced at high temperatures to generate hydrogen, which is dissolved in the liquid metal. Or when the equipment is electroplated or pickled, the steel surface is supersaturated with adsorbed hydrogen atoms, causing hydrogen to penetrate into the steel. ； It can also be absorbed from the medium after use. For example, in petroleum and chemical containers, there are many impurities containing hydrogen or hydrogen sulfide in the medium. The characteristics of hydrogen embrittlement in steel are mainly manifested in the microstructure. Decarburized ferrite of steel can often be seen on its corrosion surface, and the hydrogen embrittlement layer has corrosion cracks extending along the grain boundaries. For containers that are particularly corroded, bulges caused by hydrogen embrittlement can be seen macroscopically. Whether a container containing hydrogen (or hydrogen sulfide) in the medium will suffer from hydrogen embrittlement mainly depends on the operating temperature, partial pressure of hydrogen, action time and chemical composition of the steel. The higher the temperature and the more severe the hydrogen partial pressure, the deeper the hydrogen embrittlement layer of carbon steel and the shorter the time for hydrogen embrittlement rupture to occur. Temperature is especially an important factor. The higher the carbon content of the steel, the more serious the tendency of hydrogen embrittlement will be under the same temperature and pressure conditions. Elements such as chromium, titanium, and vanadium are added to steel to prevent hydrogen embrittlement. 　　Workpieces with hydrogen embrittlement can also be eliminated by hydrogen removal treatment (such as heating, etc.). Hydrogen embrittlement can be avoided by heating in a vacuum, low hydrogen atmosphere or inert atmosphere. For example, electroplated parts are dehydrogenated at a temperature of 200 to 240 degrees, and most of the hydrogen can be removed by heating for 2 to 4 hours. 　　Hydrogen will not cause obvious corrosion to steel at normal temperatures and pressures, but when the temperature exceeds 300°C and the pressure is higher than 30MPa, corrosion defects such as hydrogen embrittlement will occur, especially under high temperature conditions. Such as desulfurization tower, shift tower and ammonia synthesis tower in the production process of ammonia synthesis ； Some hydrogenation reaction units in the oil refining process ； Methanol synthesis tower in petrochemical production process, etc.

“And then combine into molecules inside the metal to generate very high pressure. How is this very high pressure generated?

Thanks for the explanation! ! ! Thanks for your hard work! ! ! ! !