ANS:C - resistance to vegetable acids as the tin plate are commercially used in 'canning' industry.

Though tin occurs lower than iron in the electrochemical series, it is coated on steel for corrosion protection primarily because of its resistance to vegetable acids, as tin-plated steel is commonly used in the canning industry. Explanation:

1. Electrochemical Series: The electrochemical series ranks metals according to their tendency to lose or gain electrons in a chemical reaction. Tin typically occurs lower than iron in this series, indicating that it has a lower tendency to corrode compared to iron.
2. Corrosion Protection: Despite its lower position in the electrochemical series, tin is often used to coat steel for corrosion protection due to its excellent resistance to certain types of corrosion, particularly corrosion caused by acidic environments.
3. Resistance to Vegetable Acids: Tin is highly resistant to corrosion by vegetable acids, which are commonly found in food products. When tin is plated onto steel, it forms a protective barrier that prevents the steel from coming into direct contact with the corrosive substances present in food items, thereby extending the lifespan of the steel and maintaining the integrity of the food containers.
4. Commercial Use in Canning Industry: Tin-plated steel, known as tinplate, is widely used in the canning industry to manufacture food containers such as cans and lids. The tin coating provides an inert and corrosion-resistant surface that ensures the safety and quality of the packaged food products.
5. Other Factors: While cost and availability may also influence the choice of tin as a coating material, its superior resistance to vegetable acids and its suitability for food contact applications are the primary reasons for its use in corrosion protection for steel in the canning industry.