What type of metal surface corrosion produces white or gray powdery deposits with blotches?

The type of corrosion that produces white or gray powdery deposits with blotches is typically associated with aluminum corrosion, specifically the formation of aluminum oxide. This occurs when aluminum reacts with moisture and oxygen in the environment, leading to the development of a powdery residue known as "white rust." This corrosion can compromise the structural integrity of the metal if not addressed. Similar powdery deposits can also be seen in galvanized steel, where zinc corrosion leads to white corrosion products.