Metal objects may appear black after they have been soaked in vinegar or lemon juice. However, after being rinsed in warm water, they will return to their original colors. Be careful when cleaning antiques and other valuable items. Test your rust remover in a small area first.
It is a good idea not to give children or pets rust-removal agents like vinegar, borax, baking soda. These natural ingredients may be less harsh than store-bought rust removal products, but they can still pose risks if not used correctly.