Why is it important that the surface of clad aluminum alloy not be scratched?

• A. Scratching exposes base metal and accelerates corrosion
• B. Scratching has no effect on corrosion
• C. Scratching reduces corrosion
• D. If the cladding is scratched through, corrosion will form

Answer: (D)

Clad aluminum relies on a thin protective outer layer to shield a more corrosion-prone core metal. When that cladding is scratched through, the protective barrier is lost and moisture, salts, and other corrosive elements can reach the underlying alloy, initiating corrosion at the exposed area and potentially spreading beneath the surface. If the scratch does not breach the cladding, the barrier remains intact and corrosion is much less likely. So the crucial point is that penetrating the cladding removes the protection, allowing corrosion to form.