Final answer:
Cadmium-plated finish is applied to alloys containing zinc, such as zinc-nickel alloys, to prevent surface straining and decay in aircraft.
Step-by-step explanation:
The alloys used in aircraft that have a cadmium-plated finish to prevent surface straining and decay are typically those that contain zinc. Cadmium plating is a common protection method used in the aerospace industry due to its corrosion-resistant properties. Zinc-nickel alloys, which contain a higher percentage of zinc, are often used for this purpose. By applying a cadmium-plated finish to these alloys, the surface is protected from oxidation and further corrosion.