Which of the following acids is commonly used to remove rust from metal surfaces

The acid commonly used to remove rust from metal surfaces is hydrochloric acid (HCl). Hydrochloric acid effectively reacts with iron oxides (rust) to convert them back to iron, which can then be removed. Another acid that is also frequently used is phosphoric acid (H₃PO₄), which converts rust into a more stable compound that can be easily cleaned off.

When using these acids, it is essential to take proper safety precautions, such as wearing gloves and eye protection, and ensuring adequate ventilation. After applying the acid, the metal surface should be thoroughly rinsed and dried to prevent any further corrosion.