Best way to prevent rusting of iron by making iron cathode or putting it in saline water or both

The best way to prevent rusting of iron involves several steps:

1. Cathodic Protection: This is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. A simple method of protection connects the metal to be protected to a more easily corroded "sacrificial metal" to act as the anode. The sacrificial metal then corrodes instead of the protected metal. For example, zinc is often used as a sacrificial anode for steel structures.

2. Coating: The iron can be coated with a layer of paint or oil to prevent it from coming into contact with moisture in the environment. This is a common and effective method of rust prevention.

3. Galvanization: This process involves applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanization, in which the parts are submerged in a bath of molten zinc.

4. Environmental Control: Keeping the iron in a dry environment will also help to prevent rust. This can be achieved by storing the iron in a dry place or using dehumidifiers to remove moisture from the air.

5. Alloying: Since rusting of iron is a chemical process that happens because the metal is reacting with moisture in the environment, you can prevent rust by alloying the iron with a metal that is less likely to corrode. Stainless steel, for example, is an alloy of iron and chromium (and often nickel and other metals) that is highly resistant to rust.

Putting iron in saline water is not a good way to prevent rust. In fact, it will accelerate the rusting process because salt water is an electrolyte which promotes the electrochemical reaction leading to rust.