The correct option is (c).
Explanation
Rusting is the corrosion of iron, a process that requires both oxygen and moisture (water). Prevention methods focus on isolating the metal surface from the atmosphere or modifying the metal's composition to enhance resistance.
Statement-wise Analysis
- Statement 1 is Correct: Applying a coat of paint or grease creates a physical barrier on the surface of iron. This prevents atmospheric oxygen and moisture from coming into direct contact with the metal, thereby inhibiting the oxidation process required for rusting.
- Statement 2 is Incorrect: Galvanisation is the specific process of depositing a thin layer of zinc on iron or steel to protect it from rusting. The zinc layer acts as a sacrificial anode. Deposition of chromium is known as chrome plating, which is distinct from galvanisation.
- Statement 3 is Correct: Stainless steel is an alloy obtained by mixing iron with carbon and metals such as chromium, nickel, and manganese. The presence of chromium allows the formation of a passive oxide layer that protects the underlying metal, making stainless steel highly resistant to rusting.
Key Takeaway
Galvanisation specifically involves coating iron with zinc. Stainless steel resists rust because it is an alloy containing chromium and nickel.