Introduction:
The coating of zinc iron, also known as galvanization, is a process where a layer of zinc is applied to the surface of iron or steel to protect it from corrosion. This coating acts as a sacrificial barrier, preventing the underlying metal from coming into contact with corrosive elements.

What happens when the coating of zinc iron is broken?

1. Loss of corrosion protection:
When the coating of zinc iron is broken, the underlying metal is exposed to the surrounding environment. This means that the iron or steel is no longer protected from corrosion. Corrosive elements such as moisture, oxygen, and pollutants can now directly react with the metal surface, leading to the formation of rust or other types of corrosion.

2. Formation of localized galvanic cells:
When the zinc coating is intact, it acts as a sacrificial anode and protects the iron or steel. However, when the coating is broken, a localized galvanic cell can form. This occurs when two different metals are in contact with an electrolyte (such as moisture). The metal with a higher electrochemical potential (zinc) becomes the anode, while the metal with a lower electrochemical potential (iron or steel) becomes the cathode. This leads to accelerated corrosion of the iron or steel at the site of the break in the coating.

3. Increased corrosion rate:
The presence of a break in the zinc iron coating increases the corrosion rate of the underlying metal. Corrosion can occur more rapidly at the site of the break, spreading and causing further damage to the surrounding areas. This can compromise the structural integrity of the metal object or infrastructure, reducing its lifespan and potentially leading to failure.

4. Reducing the effectiveness of zinc iron coating:
When the coating is broken, it reduces the overall effectiveness of the zinc iron coating. The protective layer is no longer continuous, allowing corrosive elements to penetrate and attack the underlying metal. This compromises the ability of the zinc to sacrificially protect the iron or steel.

Conclusion:
In summary, when the coating of zinc iron is broken, the underlying metal is exposed to corrosion, localized galvanic cells can form, the corrosion rate increases, and the effectiveness of the coating is reduced. It is important to regularly inspect and maintain zinc iron coatings to ensure their integrity and maximize their corrosion protection capabilities.