Chemical Reactions and Equations

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Corrosion is slow and steady chemical reaction. When the surface of iron or metal is in contact with moisture and other gases in the atmosphere an electrochemical reaction occurs.

After some time, a layer of hydrated oxide is formed which weakens the metal and hence metal is said to corrode.

For example: Rusting of iron, black coating on silver and green coating on copper are examples of corrosion.

A chemical reaction of iron corrosion is shown below.

The Fe²⁺ ions are oxidised to Fe³⁺ ions.
The Fe³⁺ ions combine with OH- ions to form Fe(OH)3. This becomes rust (Fe₂O₃.xH₂O) which is a hydrated ferric oxide.

Corrosion of metals is prevented by not allowing them to come in contact with moisture, CO₂ and O₂. This is achieved by the following method:

1. By coating with paints: Paint coated metal surfaces keep out air and moisture.
2. By coating with oil and grease: Application of oil and grease on the surface of iron tools prevents them from moisture and air.
3. By alloying with other metals: Alloyed metal is more resistant to corrosion example, stainless steel.

Corrosion is slow and steady chemical reaction. When the surface of iron or metal is in contact with moisture and other gases in the atmosphere an electrochemical reaction occurs.

After some time, a layer of hydrated oxide is formed which weakens the metal and hence metal is said to corrode.

For example: Rusting of iron, black coating on silver and green coating on copper are examples of corrosion.

A chemical reaction of iron corrosion is shown below.

The Fe²⁺ ions are oxidised to Fe³⁺ ions.
The Fe³⁺ ions combine with OH- ions to form Fe(OH)3. This becomes rust (Fe₂O₃.xH₂O) which is a hydrated ferric oxide.

Corrosion of metals is prevented by not allowing them to come in contact with moisture, CO₂ and O₂. This is achieved by the following method:

1. By coating with paints: Paint coated metal surfaces keep out air and moisture.
2. By coating with oil and grease: Application of oil and grease on the surface of iron tools prevents them from moisture and air.
3. By alloying with other metals: Alloyed metal is more resistant to corrosion example, stainless steel.

Redox reaction is the most important reaction in everyday life. It can be slow or fast. For example, combustion is an example of a fast redox reaction. One can easily notice heat and light.

On other hand, corrosion is slow redox reaction that occurs so slowly that noticeable heat and light are not produced.

Rancidity: The oxidation of fats and oils products when exposed to air, they become rancid and their smell and taste change.This is known as rancidity. It leads to bad smell and bad taste of food.

Methods to Prevent Rancidity

1. By adding antioxidants
2. Keeping food in airtight containers
3. Replacing air by nitrogen
4. Refrigeration