Final answer:
The surface of a piece clad aluminum alloy should not be scratched because it disrupts the protective layer of aluminum oxide, making the alloy more susceptible to corrosion.
Step-by-step explanation:
It is important that the surface of a piece clad aluminum alloy not be scratched because the formation of a strong thin layer of aluminum oxide on its surface helps resist corrosion.
Scratches can disrupt this protective layer, allowing oxygen and other substances to react with the aluminum and initiate corrosion. The integrity of the alloy can be compromised, leading to potential structural damage.