In industrial production, the degree of oxidation of titanium alloy rods may vary greatly. If the oxidation of the previous process is serious, if it is severely oxidized under high temperature conditions and becomes a scale, it must be sandblasted. After blasting the workpiece, it also needs to go through the following processes (alkali washing and pickling). If the oxide film is thin, sand blasting is required without delay, and acid pickling can be performed directly.
Titanium dioxide is an amphoteric compound, which is slightly more basic than acidic. Titanium dioxide is very thermally stable and only decomposes at very high temperatures. Its chemical stability is also very good. At low temperatures, it has good stability in many inorganic and organic media. It is insoluble in water and many other solvents, and insoluble in various dilute acids except hydrofluoric acid. Diamond dioxide is also difficult to dissolve in concentrated sulfuric acid. However, titanium dioxide is soluble in hot concentrated sulfuric acid, nitric acid, and sodium hydroxide solutions, which makes it possible to perform alkaline and acid washing on titanium screws and titanium alloy rods.
Alkaline washing of titanium alloy rods, including other rare metals, is carried out in molten alkali, and its purpose is to remove the scale on the surface of titanium alloy rods from the surface of the workpiece. The effect of lye and scale can remove scale. However, in order to remove the oxide scale from the surface of the workpiece and avoid the side effects caused by it, the oxidant (NaN03 or KNO3) must be measured in the NaoH melt.
The main parameters that affect the alkali washing process are the composition of alkali solution, the temperature and time of alkali washing.
The choice of lye composition mainly considers how the hydrogen absorption process of titanium in alkaline washing is suppressed. Titanium screws and titanium alloy rods can release hydrogen gas during alkaline washing, which provides the possibility of hydrogen absorption. Hydrogen absorption causes hydrogen embrittlement, and the lye composition has a significant effect on its hydrogen absorption. The addition of a certain component other than sodium hydroxide has a significant effect on the hydrogen absorption and the loss of gold during alkaline washing of titanium alloy rods.