A white-gray powdery deposit can usually found on which of the following metals?

Correct Answer: Option D — Aluminum.

Aluminum is highly susceptible to atmospheric corrosion, which manifests as a white-gray, powdery deposit known as aluminum oxide. This layer forms when the metal is exposed to moisture or salt-laden air. Recognizing this specific appearance is essential for identifying corrosion on aluminum components within the gas turbine intake or housing.