Galvanised steel vs painted steel – which is best for a shed?

There are lots of decisions to make when purchasing a new shed, including which material is best. One of the most common questions we hear is whether to choose galvanised steel or painted steel for a structural steel shed.

In this article, we explain what each type of steel is, the differences between them, and the benefits of each. 

We cover:

• What is painted steel?
• What is galvanised steel?
• Does galvanised steel rust?
• Coating thickness
• Scratch resistance
• Cathodic protection vs barrier protection
• Steel shed colours
• Steel costs

Click on any of the links above, to jump straight to that section.

What is painted steel?

Painted steel is steel that is sandblasted and painted with a protective coating. The coating itself is usually a thick paint that is rich in zinc, helping to reduce corrosion. Painted steel is the more traditional way to protect steel sheds against the elements.

However, this paint is softer and the application thickness can vary. Over time, the paint is susceptible to chips and scratches which exposes the underlying metal to corrosion.

Key characteristics of painted steel

• Thickness ranges between 64 µm to 90 µm.
• Not resistant to scratching.
• Uneven coverage.
• Does not provide cathodic protection. 
• Wide range of colours. 

What is galvanised steel?

Galvanised steel, also known as hot-dip galvanised steel, is steel that has been covered in a zinc coating. The galvanisation process involves thoroughly cleaning the steel to remove any impurities and dipping it in a molten zinc solution. The liquid zinc sticks to the metal and hardens upon removal.

The outer layer of zinc provides the inner core with corrosion protection from moisture and other corrosive elements.

Key characteristics of galvanised steel

• Cathodic and barrier protection.
• An average thickness of 85 µm.
• Scratch-resistant.
• Even coverage and complete protection.
• Greater hardness and corrosion resistance.
• Less maintenance over time.
• Not as cost-effective as painted steel.

Does galvanised steel rust?

While hot-dipped galvanised steel will rust eventually in higher corrosive environments, it typically resists corrosion for much longer than uncoated steel. That’s because the zinc coating oxidises instead of the core steel, slowing the rate of corrosion and preserving the building’s structural integrity. 

Galvanised vs painted steel – which is better?

All steel sheds should be sealed with either paint or a galvanised zinc coating. Ultimately, the coating acts as a sacrificial layer, being exposed to oxidisation before the steel itself.

However, the coating will eventually deteriorate with time, eventually leaving the core steel open to the elements too. So the question is – which coating will ensure a longer lifespan for your steel shed? Consider the following factors. 

Coating thickness

The protective layer on painted steel is uneven and generally thinner. While some manufacturers apply the paint in factory-controlled conditions, it is still more inconsistent than galvanised steel. On average, the thickness of painted steel is between 64 µm and 90 µm, compared to the average thickness of 85 µm for galvanised steel. For advice, speak with our steel experts. 

Scratches and surface damage

Painted steel is prone to scratches, which will expose the core material to oxidation and moisture. This can occur as soon as your shed is built, leading to immediate cases of rust. On the other hand, galvanised steel is scratch-resistant, protecting the core steel for many years.

Cathodic protection

Unlike painted steel, galvanised steel provides cathodic protection as well as barrier protection. This is when two metals have different electrode potentials and corrode at different rates. The anode is the lesser of the two, meaning it is more reactive and more prone to corrosion. The cathode is the more noble metal, is less reactive, and will corrode at a much slower rate.

In other words, the anode is sacrificial, allowing the cathode component to last much longer. 

Shed colours

If the colour of your new shed is a deciding factor, painted steel offers more options. From crisp white to forest green to matt black, you can customise your shed colour to complement your surrounding environment, company branding, and your personal taste. On the other hand, galvanised steel is usually only available in silver.

At ABC Sheds, we can offer the best of both worlds because our sheds are not only hot-dip galvanised, but the cladding can also be finished with COLORBOND® steel. This steel is tough, robust, and available in 22 striking colours. Popular colours for sheds include Monument Black, Classic Cream, Pale Eucalypt, and Ironstone. Find your favourite in the COLORBOND® pallet or browse our projects to see them in situ. 

Steel costs

Painted steel is generally more affordable than galvanised steel, but only in terms of upfront cost. Over time, the maintenance and replacement costs will be much higher for painted steel. In most cases, it is more cost-effective to invest in high-quality hot-dip steel that will last for decades with minimal upkeep required. 

Structural Steel Sheds Australia

The ABC Sheds team is here to guide you through the design and construction of your structural steel shed. Simply contact us and we will take you through the options available.

For more details on the sheds we manufacture you can also take a look at our full brochure, where you will find all the answers you need about our farm sheds, hay sheds and grain sheds, feedlot shelters and yard covers, dressage arenas, industrial sheds, aircraft hangars, and more.

All of our sheds are built with structural steel to withstand the harsh Australian climate. Key benefits of working with us include: 

• A fully fabricated and galvanised structural steel frame.
• 25-year guarantee.
• Customised designs.
• Hassle-free shed erection.
• Australian building standards exceeded.
• The Durakit range for faster delivery. 
• Monthly super deals.

If you’re interested to see what kind of shed we can build for you, use our virtual shed builder tool. You can select the type of shed you want, adjust the specifications, and request an accurate quote from our experts. The tool will show you how your new shed will look and function so you can visualise how it will support your operations.