🔍 Key Concepts

• Corrosion products and what they look like on different metals • How aluminum, magnesium, and steel typically corrode in air and saltwater • The usual color and texture of oxide layers on common shipboard metals

💭 Think About

• For each metal in the choices, picture what its common corrosion or oxidation product looks like (color, texture). Which one is commonly described as a white to gray, powdery deposit? • Think about rust on steel—what color is it usually? Think about magnetite—what color is that mineral? Do either of those match white-gray powder? • Between aluminum and magnesium, which one is more commonly noted in basic seamanship/engineering texts as forming a light, white-gray, powdery surface corrosion?

✅ Before You Answer

• Eliminate any metals whose corrosion products you know are definitely not white or gray (for example, clearly reddish-brown or black). • Compare aluminum oxide and magnesium oxide in your memory—consider which is more often mentioned in marine contexts as a white-gray powder on fittings and structures. • Remember that magnetite (Fe₃O₄) has a very specific, well-known color—verify whether it fits "white-gray powder" before you keep it as a candidate.