18th March 2025
Introduction
Corrosion is an age-old enemy of metal, a pervasive problem that shortens the life span of metal structures and components. One of the most effective ways to combat this issue is through galvanisation, a process that coats metal with a layer of zinc to offer a sturdy shield against corrosion. Two common methods are hot-dip galvanising and hot zinc spraying. While hot-dip galvanising has its merits, it isn’t always practical for large or awkwardly shaped items. This is where hot zinc spray shines as the optimal choice.
What is Hot Zinc Spray?
Hot zinc spray, also known as metallising, thermal spraying, or zinc spraying, is a process where zinc wire is melted and atomised using compressed air and high-velocity oxygen fuel (HVOF) or electric arc spray systems. The atomised particles are then sprayed onto the prepared surface of the item, creating a robust zinc coating.
Process of Applying Hot Zinc Spray
- Surface Preparation: Before applying the hot zinc spray, the surface of the metal is thoroughly cleaned to remove rust, paint, and other contaminants. This often involves shotblasting.
- Priming: Depending on the application, a primer may be applied to further improve adhesion.
- Spraying: Using specialised equipment, molten zinc is sprayed onto the item. The zinc adheres to the surface and immediately solidifies upon impact, creating a coating.
- Sealing: After spraying, a sealant can be applied to improve the coating’s durability and corrosion resistance.
- Quality Check: Finally, the item is inspected for complete coverage and thickness, ensuring the coating meets all standards and specifications.
Why Hot Zinc Spray is Perfect for Large, Awkward-Shaped Items
Versatility
Hot zinc spray is highly versatile and can be applied to items of virtually any size and shape. This includes intricate structures like bridges, large tanks, and irregularly shaped machinery.
Uniform Coverage
Unlike hot-dip galvanising, which may struggle to coat areas where the liquid zinc can’t easily reach, hot zinc spray can be directed to coat every nook and cranny evenly.
On-Site Application
One of the major advantages is the feasibility of on-site application. This eliminates the need for transporting large items to a galvanising facility.
Lower Heat Distortion
The hot zinc spray process is less likely to cause heat distortion, making it ideal for thinner and more delicate metal items.
Cons of Hot-Dip Galvanizing
Size Limitations
The dimensions of the galvanising bath limit the size of items that can be hot-dip galvanised. Large or awkwardly shaped items may not fit, making hot-dip galvanising impractical.
Incomplete Coverage
Internal or hidden surfaces are often not adequately coated in a hot-dip process, leading to uneven protection.
Transportation Issues
Transporting large, heavy items to a galvanising facility can be logistically challenging and costly.
Heat Distortion
Hot-dip galvanising requires the entire item to be immersed in molten zinc, which can cause heat distortion, particularly in thinner metals.
Conclusion
For large, awkwardly shaped items, hot zinc spray offers a superior, more versatile solution for combating corrosion. With its ability to provide even coverage, apply on-site, and lower heat distortion risks, hot zinc spray is clearly a wise choice for many applications. While hot-dip galvanising has its place, its limitations with large or complex structures make hot zinc spray a compelling alternative. At NSP Coatings we offer Hot Zinc Spray in-house and we believe it leaves a superior coating allowing a much better end finish to the item. Let our experts help you decide if HZS is the right application for your item.
