Corrosion is the damage or qualitative change of material under the influence of the environment. The corrosion of metal and alloy is mainly caused by chemical or electrochemical damage. Common corrosion-resistant metals are austenitic stainless steel, Hastelloy, Monel alloy, titanium and titanium alloy, platinum, gold, rhodium and other precious metals. Few people know that the corrosion-resistant star material is tantalum. Tantalum has a good corrosion resistance. It can be called a wise choice for dealing with the problem of corrosion. Although tantalum is not a precious metal, it is comparable to precious metals in terms of chemical resistance. In addition, tantalum is easy to process in conditions that are significantly lower than room temperature. With its good corrosion resistance, tantalum plays a very important role in many chemical applications.
At room temperature, only the following inorganic substances can make tantalum lose tolerance: concentrated sulfuric acid, fluorine gas, hydrogen fluoride, hydrofluoric acid and acidic solutions containing fluoride ions. Additionally, alkaline solution, molten sodium hydroxide and potassium hydroxide can also cause corrosion of tantalum. But on the contrary, this material is resistant to aqueous ammonia solutions. If tantalum is chemically invaded, hydrogen will enter its metal lattice, causing the material to become brittle. As the temperature gradually increases, the corrosion resistance of tantalum will gradually decline. Whether in cold or hot conditions, it won’t react with hydrochloric acid, concentrated nitric acid and “aqua regia”. Tantalum can be corroded in hot concentrated sulfuric acid. Below 150 degrees, tantalum will not be corroded by concentrated sulfuric acid. Reaction will only take place above this temperature. Soaked in concentrated sulfuric acid of 175 degrees for one year, tantalum’s thickness of corrosion is 0.0004mm. Soaked in sulfuric acid of 200 degrees Celsius, the surface damage is only 0.006mm.
The corrosion resistance of pure tantalum is very good. The corrosion resistance of tantalum tungsten alloy is far better. Ta10W and Ta2.5W have higher corrosion resistance than that of pure tantalum. However, due to the addition of tungsten, the material becomes harder and crisper, and the cost is much higher than that of pure tantalum.
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