When working with steel in outdoor, water-prone, or corrosive environments, protection is everything. One of the most reliable and widely used methods for safeguarding steel is hot-dip galvanising. But what exactly does this process involve, and why is it such a trusted solution?
In this blog, we’ll walk you through how hot-dip galvanising works, why zinc is used, and how it compares to other galvanising methods.
What is Hot-Dip Galvanising?
Hot-dip galvanising is a process where steel or iron is coated in a layer of zinc to protect it from corrosion. The steel is immersed in a bath of molten zinc, forming a tough, bonded coating that protects the metal from rust, environmental damage, and long-term wear.
This technique is commonly used for outdoor structures such as grating walkways, safety barriers, architectural facades, and infrastructure components — essentially, any application where steel is exposed to the elements.
Why Use Zinc?
Zinc offers two critical advantages:
- Bonding Strength – Zinc reacts with the iron in steel to form a tightly bonded alloy layer. This metallurgical bond makes the coating extremely difficult to damage or remove.
- Corrosion Resistance – Zinc is naturally resistant to corrosion, and even if the surface is scratched, it continues to protect the steel underneath through a process called cathodic protection. It’s also self-healing to a degree and highly sustainable.
In fact, zinc has been used in construction for thousands of years — with formal hot-dip galvanising processes developed in the 19th century and continuously refined ever since.
The Hot-Dip Galvanising Process (Step-by-Step)
Here’s how the process works, typically when galvanising a steel sheet or fabricated component:
1. Surface Cleaning
Before galvanising, all contaminants (dirt, grease, oil, and paint) must be removed from the steel surface. This is usually done with a degreasing solution and mild acid. Clean surfaces are essential for proper zinc bonding.
2. Descaling
To remove mill scale and iron oxides, the steel goes through a diluted solution of heated sulfuric acid or ambient hydrochloric acid.
3. Fluxing
After pickling, the steel is treated with a flux (often zinc ammonium chloride) to prevent further oxidation before dipping. This step prepares the metal for the molten zinc bath.
4. Galvanising (Hot-Dip)
The cleaned and prepped steel is submerged in a bath of molten zinc heated to around 450°C. During immersion, a metallurgical reaction occurs, forming protective zinc-iron alloy layers on the steel’s surface. This process typically takes just a few minutes.
6. Inspection
The final step is quality inspection. Galvanised coatings are tested for thickness, appearance, and uniformity according to industry standards and local regulations.
Why Galvanise Steel?
Hot-dip galvanising offers significant long-term benefits:
- Durability: The bonded zinc coating offers decades of protection — often exceeding 50 years in some environments.
- Full Coverage: Dipping ensures complete surface protection, even on edges, corners, and recesses. This is especially important for our Monowills safety barrier and grating.
- Sustainability: Zinc is 100% recyclable, and about 30% of all zinc used today comes from recycled sources. Better still, galvanised steel remains fully recyclable at end-of-life.
- Low Maintenance: Galvanised steel requires far less upkeep over time compared to painted or untreated steel.
- Cost-Effective: The initial cost of galvanising is offset by long-term savings in maintenance, repairs, and replacement.
How Does It Compare to Other Methods?
While hot-dip galvanising is the most common, there are other zinc coating methods:
Hot-dip galvanising stands out as fast, proven, and widely applicable, offering the best combination of strength, longevity, and speed of application.
Hot-Dip Galvanising at Webforge
At Webforge, we hot-dip galvanise our steel grating and monowills products to ensure they can withstand even the harshest conditions. From industrial walkways to custom architectural components, our galvanising process ensures your materials are protected for the long haul.
Want to learn more about our galvanised steel products or how we can help with your next project? Contact our team today — we're here to help you build with confidence.