Why is galvanising more effective than just coating with paint?

Galvanising is more effective than just coating with paint because it provides superior corrosion resistance and durability.

Galvanising is a process where a protective layer of zinc is applied to iron or steel to prevent rusting. This is more effective than just painting because the zinc layer actually bonds with the underlying metal, creating a barrier that is much more resistant to corrosion and wear.

When iron or steel is galvanised, the zinc reacts with the oxygen in the air to form zinc oxide. This zinc oxide then reacts with carbon dioxide in the air to form zinc carbonate, a dull grey, fairly strong material that stops further corrosion. This process is known as 'sacrificial protection' because the zinc is sacrificed to protect the iron or steel.

On the other hand, paint is simply a coating that sits on the surface of the metal. It can easily chip or peel off, exposing the underlying metal to the elements and allowing it to rust. Paint also does not provide the same level of protection against corrosion as galvanising does.

Furthermore, galvanising provides a thicker, more durable layer of protection than paint. The galvanised coating is typically 50-100 microns thick, compared to a typical paint coating which is only around 20 microns thick. This means that galvanised surfaces are more resistant to damage from impact, abrasion, and other forms of wear and tear.

In addition, galvanising is a one-time process that can last for decades without the need for maintenance, whereas painted surfaces need to be regularly maintained and repainted to keep them protected. This makes galvanising a more cost-effective and time-saving solution in the long run.

In conclusion, while both galvanising and painting can provide some level of protection against corrosion, galvanising is generally more effective due to its superior durability, thickness, and sacrificial protection.