The metal dissolves in the pickling solution, accompanied by the electron transfer on the metal atom, so the electrochemical corrosion phenomenon is the main cause. The result of metal atoms losing electrons is the formation of metal ions. For example, grade 5 titanium bar loses electrons in reducing acid and becomes trivalent titanium ion.
The pickling of titanium alloy rod processed materials is carried out in a mixed acid solution containing hydrofluoric acid or fluoride. When pickling, hydrogen ions may be reduced to form atomic hydrogen or molecular hydrogen. Atomic hydrogen has a tendency to diffuse into the metal, which may cause hydrogen embrittlement.
When titanium is pickled in a nitric acid solution containing fluoride ions, the gr5 titanium foil is oxidized and nitric acid is reduced. The final product is the formation of a titanium fluoride complex, water, and colorless nitric oxide.
If exposed to the atmosphere, nitric oxide quickly oxidizes into brown toxic nitrogen dioxide when it encounters oxygen in the air and volatilizes.
Therefore, when pickling, try to expel nitrogen dioxide quickly through ventilation. If about 0.5% H202 is added to the pickling solution, the NO will be oxidized in the solution and it will escape from the liquid surface so that the air pollution is appropriately reduced.
When pickling titanium wire in a nitric acid solution containing 5% -7% fluoride ion, if the mass fraction of oxidant nitric acid is less than 15%, the over-potential of various reduction reactions in the solution determines the hydrogen ion is more The chance of reduction, and after being reduced to hydrogen atoms, it will be sucked into the titanium in a certain ratio, diffuse to some parts of the alloy to gather or generate titanium hydride to cause hydrogen embrittlement. Therefore, in order to prevent the hydrogen absorption of titanium materials during acid pickling, the ratio of nitric acid to hydrofluoric acid should always be kept greater than 5. However, if the content of nitric acid is too large, the reaction will be slow, the production efficiency will be reduced, and the flue gas will be produced, making the operation difficult.
The pickling of titanium alloy rod processed materials is carried out in a mixed acid solution containing hydrofluoric acid or fluoride. When pickling, hydrogen ions may be reduced to form atomic hydrogen or molecular hydrogen. Atomic hydrogen has a tendency to diffuse into the metal, which may cause hydrogen embrittlement.
When titanium is pickled in a nitric acid solution containing fluoride ions, the gr5 titanium foil is oxidized and nitric acid is reduced. The final product is the formation of a titanium fluoride complex, water, and colorless nitric oxide.
If exposed to the atmosphere, nitric oxide quickly oxidizes into brown toxic nitrogen dioxide when it encounters oxygen in the air and volatilizes.
Therefore, when pickling, try to expel nitrogen dioxide quickly through ventilation. If about 0.5% H202 is added to the pickling solution, the NO will be oxidized in the solution and it will escape from the liquid surface so that the air pollution is appropriately reduced.
When pickling titanium wire in a nitric acid solution containing 5% -7% fluoride ion, if the mass fraction of oxidant nitric acid is less than 15%, the over-potential of various reduction reactions in the solution determines the hydrogen ion is more The chance of reduction, and after being reduced to hydrogen atoms, it will be sucked into the titanium in a certain ratio, diffuse to some parts of the alloy to gather or generate titanium hydride to cause hydrogen embrittlement. Therefore, in order to prevent the hydrogen absorption of titanium materials during acid pickling, the ratio of nitric acid to hydrofluoric acid should always be kept greater than 5. However, if the content of nitric acid is too large, the reaction will be slow, the production efficiency will be reduced, and the flue gas will be produced, making the operation difficult.
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