The corrosion of antennas mounted on which material can be identified by a white or grayish white powder?

The correct choice is aluminum because this metal undergoes a specific type of corrosion known as "aluminum oxide formation." When aluminum is exposed to moisture and oxygen, it reacts to form aluminum oxide, which appears as a white or grayish white powder. This powder is a byproduct of the corrosion process and is a visible indicator that the aluminum has begun to corrode.

This characteristic powder helps in the identification of corrosion damage on aluminum antennas or components. Recognizing this corrosion early is essential for maintenance and preventing further degradation of structural integrity.

In contrast, steel typically rusts and forms reddish-brown iron oxide, plastic does not corrode in the same manner as metals and is more resistant to degradation, and copper corrosion presents as greenish patina rather than a white or grayish powder. Understanding these distinctions aids in quick identification and remediation of corrosion issues in avionics and related systems.