The Galvanising Process And How It Helps Protect Structural Steel

3 May 2020

What exactly does it mean to ‘galvanise’ steel?

And, more importantly, why should you?

Quite simply:

It’s about protecting steel against corrosion.

You see galvanised steel is more resistant to corrosion and rust. And when we say more resistant, we’re talking by a number of years.

Decades even.

This long-lasting protection is crucial, especially when it comes to structural steel.

When you’re erecting warehouses, constructing factories or designing offshore platforms that must stand for decades to come…

It’s important the structural steel you’re using in the construction is able to stand up against all the elements.

This is where galvanisation comes in.

The process itself was named after an Italian scientist called Luigi Galvani, who discovered the electromagnetic process that takes place between certain metals.

Strangely, it’s reported he discovered it during an experiment on frogs’ legs.

Right now, though, let’s look at how the galvanisation process actually works…

The secret weapon in the galvanising process

As we say, in simple terms, to galvanise refers to the process of coating steel or iron with zinc.

That’s the secret weapon here:


The zinc coating protects the steel beneath it by reacting to the elements first. Because of its chemical make up, it is a lot more resistant to the different elements that lead to corrosion.

In fact, even if there is damage to the zinc – and a small part of the steel is exposed – the zinc around the exposed area STILL helps prevent corrosion. (Usually within a 5mm radius.)

This quality is unique to zinc, and explains why it’s used in the process, as opposed to other metal elements.

Of course, you might be wondering how you actually coat steel in zinc?

Bath time

The most common method of galvanising steel is to ‘hot dip’ it in a molten ‘bath’ of zinc.

This is where the zinc is heated to around 450 degrees before the steel is dipped into it.

When the steel reaches the same heat as the zinc, it’s removed and placed in what’s known as a ‘quench tank’. This cools the now galvanised steel accordingly.

Once cooled, you can often tell the steel has been galvanised because of a white-grey, crystallised pattern on the steel.

This patterning is known as ‘spangling’ and is created by the crystallisation of the zinc around the steel.

Galvanised steel can still be welded, but it’s important to do so carefully as the fumes generated by the zinc coating can be dangerous.

Decades of experience

Despite the incredible temperatures at which galvanisation occurs and the sheer size of some of the structural steel that requires coating…

It’s a delicate process that requires a lot of expertise.

It’s why we’ve spent decades developing strong relationships with a number of galvanisation specialists who we trust to protect the structural steel we use in all our projects.

Should your project require such finishing, we’ll take care of organising the entire process and make sure your structural steel is protected against all the elements.

To find out more about the galvanisation process, or to discuss a steel fabrication or erections project you’re working on and would like support on, just get in touch.

You can email us at or call direct on 01469 540 644 and a member of our friendly team of experts will be able to discuss your needs.

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