How does the presence of impurities such as copper affect the rusting of a piece of sheet metal of iron?

Answer 1

Any answer choices?

Answer 2

On steel ships, corrosion is greatly increased by having bronze (copper alloy) propellers. Current will flow from the props thru the (salt bridge) seawater, turning the Fe to Fe++. Copper embedded in the steel will do the same. http://www2.ucdsb.on.ca/tiss/stretton/chem2/corrosion.html