Question

• How can you prevent iron from rusting?

Answer 1

Rusting: Rusting of iron refers to the formation of rust, a mixture of iron oxides, on the surface of iron objects or structures.

• This rust is formed from a redox reaction between oxygen and iron in an environment containing water (such as air containing high levels of moisture).
• $\mathrm{Iron}\left(\mathrm{Fe}\right)+\mathrm{Oxygen}({\mathrm{O}}_2,\mathrm{from}\mathrm{the}\mathrm{air})+\mathrm{water}\left({\mathrm{H}}_2\mathrm{O}\right)\to \mathrm{rust}(\mathrm{iron}\mathrm{oxide}{\mathrm{Fe}}_2{\mathrm{O}}_3).$
• The rusting of iron is characterized by the formation of a layer of a red, flaky substance that easily crumbles into a powder.

Factors that Affect the Rusting of Iron:

Many factors speed up the rusting of iron, such as the moisture content in the environment and the pH of the surrounding area. Some of these factors are listed below.

1. Moisture: The corrosion of iron is limited to the availability of water in the environment. Exposure to rain is the most common reason for rusting.
2. Acid: if the pH of the environment surrounding the metal is low, the rusting process is quickened. The rusting of iron speeds up when it is exposed to acid rain. Higher pH inhibits the corrosion of iron.
3. Salt: Iron tends to rust faster in the sea, due to the presence of various salts. Saltwater contains many ions that speed up the rusting process via electrochemical reactions.

Prevention from rusting:

Iron and its alloys are widely used in the construction of many structures and in many machines and objects. Therefore, the prevention of the corrosion of iron is very important. Some preventive methods are listed below.

1. Alloys that are Resistant to Rusting

• Some alloys of $\mathrm{iron}$ are rust-resistant. Examples include stainless steel (which features a layer of chromium(III) oxide) and weathering steel.
• In this alloy, the rust forms a protective layer on the surface of the alloy, preventing further corrosion.

2. Galvanization:

• Galvanization is the process of applying a protective layer of $\mathrm{zinc}$ on a metal. It is a very common method of preventing the rusting of iron.
• This can be done by dipping the metal to be protected in hot, molten $\mathrm{zinc}$ or by the process of electroplating.

3. Cathodic Protection:

• Providing the metals with an electric charge can help inhibit the electrochemical reactions that lead to rusting.
• This can be done by making the $\mathrm{iron}$ a cathode by attaching a sacrificial anode to it.
• This sacrificial anode must have an electrode potential that is more negative than that of $\mathrm{iron}$.

4. Coatings:

• Many types of coatings can be applied to the surface of the exposed metal in order to prevent corrosion.
• Common examples of coatings that prevent corrosion include paints, wax tapes, and varnish.