In the production process of titanium and titanium alloy materials, removing the oxide scale is a crucial step, and titanium pickling is the main means to achieve this goal. Before pickling, titanium materials usually need to be pretreated, such as molten alkali washing, mechanical descaling, or sandblasting, to remove most of the dirt and thick oxide layer on the surface, creating favorable conditions for subsequent pickling.
For the slight titanium oxide film formed below 600°C, titanium pickling is a very effective removal method. During the pickling process, titanium reacts chemically with the acid to form metal ions, thereby removing the oxide scale. However, titanium pickling is not just a simple chemical reaction, it also involves electrochemical phenomena.
When pickling in a mixed acid containing hydrofluoric acid or fluoride, special attention should be paid to the reduction reaction of hydrogen ions. These hydrogen ions may be reduced to atomic hydrogen or molecular hydrogen. Among them, molecular hydrogen tends to diffuse into the interior of the metal. Once it enters the interior of the metal, it may cause hydrogen embrittlement of the metal, seriously affecting the performance and service life of the titanium material.
Therefore, when titanium pickling materials, the composition and proportion of the acid solution must be strictly controlled to prevent the occurrence of hydrogen absorption. In particular, the ratio of nitric acid to hydrofluoric acid must always be kept greater than 5. Control of this ratio is crucial to preventing hydrogen embrittlement. However, it is also necessary to note that the nitric acid content should not be too high, because too high a nitric acid content will lead to a decrease in reaction speed and production efficiency, and will also produce a large amount of smoke, which will bring difficulties to the operation.
In addition, attention should be paid to the control of process parameters such as temperature and time during the titanium pickling process. Too high a temperature or too long a time may cause excessive corrosion of titanium materials and affect the surface quality. Therefore, in actual operation, it is necessary to reasonably adjust the pickling process parameters according to factors such as the material, thickness, and severity of the scale of the titanium material to ensure the optimization of the pickling effect.
In short, the titanium pickling process of titanium and titanium alloy processing materials is a complex and delicate task. Only by strictly controlling the composition, proportion, and process parameters of the acid solution can the pickling effect be ensured while avoiding unnecessary damage to the titanium material. Interested friends can continue to follow our sharing to learn more about the knowledge and technology of titanium metal in production.
