The purpose of coating food cans is to prevent the underlying iron (steel) from rusting and to prevent the metal from reacting with the food inside. In the reactivity series of metals, Zinc is above Iron and Tin is just above Lead. This means Zinc is more reactive than both Iron and Tin. If Zinc were used as a coating, it would be more likely to react with acidic components in the food, forming potentially harmful compounds. Tin, being less reactive than Zinc and also less reactive than Iron in many conditions relevant to food storage, provides a more stable and inert protective layer. While tin is also above iron in the reactivity series, the reaction rate is often slower, and tin is considered safer for contact with food compared to zinc.