Which metals are specifically targeted for chemical removal using the phosphoric acid/water mixture?

Which metals are specifically targeted for chemical removal using the phosphoric acid/water mixture?

• A. Iron and steel
• B. Titanium
• C. Aluminum and magnesium
• D. Copper and brass

Answer: (A)

Phosphoric acid in water is used as a rust-removing treatment for ferrous metals. It chemically converts iron oxide (rust) on iron and steel into iron phosphate, forming a layer that can be rinsed away and often leaves a protective, slightly rough coating that helps subsequent coatings adhere. This makes the mixture particularly effective for iron and steel, where rust is a common form of corrosion and the reaction directly targets that oxide. Aluminum and magnesium, titanium, and copper/brass don’t respond to this treatment in the same practical way. Their oxides and surfaces require different cleaning or pretreatment methods, and reacting with phosphoric acid can lead to unwanted changes or damage rather than the controlled rust removal seen on ferrous metals.

Phosphoric acid in water is used as a rust-removing treatment for ferrous metals. It chemically converts iron oxide (rust) on iron and steel into iron phosphate, forming a layer that can be rinsed away and often leaves a protective, slightly rough coating that helps subsequent coatings adhere. This makes the mixture particularly effective for iron and steel, where rust is a common form of corrosion and the reaction directly targets that oxide.

Aluminum and magnesium, titanium, and copper/brass don’t respond to this treatment in the same practical way. Their oxides and surfaces require different cleaning or pretreatment methods, and reacting with phosphoric acid can lead to unwanted changes or damage rather than the controlled rust removal seen on ferrous metals.