ASA Aviation Maintenance Technician General Practice Test

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.