Generally speaking, titanium tube is the preferred metal material for heating equipment of nitric acid solution. Baoji titanium pipe has better corrosion resistance in oxidizing media (such as nitric acid, chromic acid, hypochlorous acid and perchloric acid, etc.). In reducing acids, the addition of heavy metal salts can play a significant role in corrosion inhibition. The corrosion resistance of titanium palladium alloy and titanium nickel molybdenum alloy is much higher than that of industrial pure titanium.
In reducing acid (such as dilute sulfuric acid solution, hydrochloric acid solution, etc.), due to the destruction of the passivation of the oxide film, the corrosion rate is relatively fast, and it increases with the increase of temperature and concentration. The titanium heat exchanger is subjected to 60% nitric acid at about 193°C, and no corrosion has been found after many years of use. In the boiling 40% and 68% nitric acid, there was some corrosion at the beginning. After a short time, the passiveness of titanium recovered and the corrosion rate was significantly reduced. It may be related to the corrosion inhibition effect of titanium ions.
If the temperature is so high that the solution boils, the sulfuric acid temperature will still corrode even if it drops to 0.5%. When nitrogen is introduced into the sulfuric acid solution at the same temperature, the corrosion rate of titanium is significantly higher than that of air. This corrosion law is basically the same in other reducing inorganic acids. In the sulfuric acid with air at room temperature, industrial pure titanium can only withstand sulfuric acid solutions below 5%; if the temperature drops to about 0°C, the sulfuric acid concentration can be increased to 20%.
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