A new high strength lightweight metal composite is made of magnesium reinforced with iron and aluminum fibres. When the composite is used in a marine environment, a sudden unexpected loss of strength in the composite occurs after a few weeks. What is a possible cause of this strength loss? 

A nickel alloy, used for high strength at elevated temperatures gives reliable service in nitrogen, argon atmospheres but fails rapidly in open air. Suggest the likely cause for this loss of strength. 

In extremely intense building fires, the steel framework of the building was observed to have been largely destroyed beyond leaving traces of once molten iron. The aluminum superstructure of a ship was observed to burn during an onboard fire. Discuss the fundamental reasons for uncontrolled burning and even melting of normally passive metals such as iron and aluminum.