What chemical is used to remove corrosion from titanium?

• A. Hydrochloric acid
• B. Sodium hydroxide
• C. Nitric hydrofluoric acid
• D. Chromic acid

Answer: (C)

To remove corrosion from titanium, you need an etchant that can break through its tough native oxide layer without excessively attacking the metal itself. A mixture of nitric acid and hydrofluoric acid does just that: HF dissolves the titanium oxide and forms soluble fluorides, while nitric acid helps maintain an oxidizing environment that promotes uniform cleaning and impurity removal. This combination is specifically used for titanium surfaces in pickling and corrosion control because it overcomes the oxide barrier that protects titanium and reveals a clean metal surface for coatings or further processing. The other acids listed either don’t effectively remove the oxide layer on titanium (for example, hydrochloric acid can be too harsh or inadequate for oxide dissolution), are not suitable for this purpose (sodium hydroxide is caustic and not an oxide remover for titanium), or are used for different materials and processes (chromic acid is typically used for stainless steels and aluminum passivation rather than titanium).