Which cleaning agent should be avoided on aluminum structures to prevent corrosion?

• A. Caustic cleaning products
• B. Water
• C. Neutral detergents
• D. Mild solvents

Answer: (A)

Caustic cleaning agents should be avoided on aluminum structures because their strong alkaline nature attacks the protective oxide film that aluminum forms. When exposed to high pH cleaners, aluminum reacts with the base to form soluble aluminates and hydrogen gas, leading to rapid corrosion, etching, and weakening of the metal. Mechanistically, a reaction like aluminum plus a strong base in water yields sodium aluminate and hydrogen, which disrupts the surface protection. Water and neutral detergents don’t react with the oxide layer, so they’re generally safe if used and rinsed properly, and mild solvents are typically acceptable when compatible with aluminum and used correctly.