8th October 2024
Rust, the arch-nemesis of metal, has plagued structures, vehicles, and tools since iron was first forged. Protecting metal from rust is essential to ensure longevity and durability in industries such as construction, automotive, and manufacturing. From ancient methods to cutting-edge technology, there are numerous ways to safeguard metal from corrosion. One of the most effective solutions is zinc coating, a method with a rich history and a variety of techniques. In this article, we’ll explore the history of zinc coatings and delve into the different methods available to protect metal from rust, focusing especially on galvanising and Zinc Spray, also known by other names.
The History of Zinc Coatings
Zinc has been used for centuries as a protective coating for metal. The practice of using zinc to protect iron and steel dates back to the 18th century. Luigi Galvani, an Italian scientist, is credited with the discovery of galvanisation, though it was initially observed in the context of electrical currents. The term “galvanising” was later adopted to describe the process of coating iron with zinc to prevent rust.
The earliest documented use of zinc for rust prevention occurred in France in 1837, when Stanislas Sorel patented the process of hot-dip galvanising, in which steel is dipped into molten zinc to form a protective layer. This was a groundbreaking development in corrosion protection and is still widely used today.
Since then, the technology has evolved significantly, with new techniques like Hot Zinc Spray becoming popular alternatives for protecting metal surfaces.
How Does Rust Form?
Before diving into the protection methods, it’s essential to understand how rust forms. Rust, or iron oxide, forms when iron or steel reacts with oxygen in the presence of moisture. The combination of water and air creates an electrochemical reaction that deteriorates the metal surface over time. Left untreated, rust can weaken and destroy metal, leading to costly repairs and replacements.
Methods for Protecting Metal from Rust
There are various methods for protecting metal from rust. These methods typically involve either creating a barrier to prevent moisture and oxygen from reaching the metal or using a sacrificial layer to protect the steel or iron beneath. Let’s explore the most common and effective ways to protect metal from corrosion.
- Paint and Powder Coating
The simplest way to protect metal from rust is to apply a layer of paint or powder coating. Paint creates a physical barrier that prevents moisture and oxygen from reaching the surface of the metal. Similarly, powder coating is a durable, protective finish applied as a dry powder and cured under heat. The powder coating procedure is especially effective for providing a long-lasting finish that resists rust.
However, while paint and powder coatings provide aesthetic and protective benefits, they are not as durable in harsh environments where metal is exposed to saltwater or heavy industrial use. Over time, the coating may chip or crack, exposing the underlying metal to corrosion.
- Oil or Grease Coating
Applying oil or grease to metal surfaces can also provide rust protection by creating a barrier against moisture. This method is commonly used for tools, machinery, and mechanical parts that may be exposed to moisture or condensation. The oil or grease prevents water from making contact with the metal surface, thereby reducing the risk of rust.
While oil and grease are effective for some applications, they are not suitable for permanent protection or outdoor use as they can easily wear off, requiring frequent reapplication.
- Galvanising
Hot-dip galvanising, one of the most popular methods for protecting metal from rust, involves dipping steel or iron into molten zinc. The zinc coating acts as a sacrificial barrier, meaning the zinc corrodes before the steel or iron does, effectively protecting the metal underneath.
The beauty of galvanising lies in its dual protection:
- Barrier Protection: The zinc layer physically prevents moisture and air from reaching the metal surface.
- Cathodic Protection: Even if the zinc layer is scratched or damaged, the zinc will corrode before the metal, offering protection in areas where the coating may have been compromised.
Pros of Hot-Dip Galvanising:
- Long-lasting protection in harsh environments.
- Low maintenance and cost-effective for large structures.
- Suitable for both industrial and architectural applications.
Cons of Hot-Dip Galvanising:
- The process leaves a thick, uneven layer of zinc, often requiring fettling (the removal of excess material) to smooth out the surface.
- After fettling, some of the protective zinc layer may be lost, potentially compromising corrosion resistance.
- Aesthetic finishes are harder to achieve due to the rough texture.
- Hot Zinc Spray (Arc Spray)
If you’re looking for a smoother, more controlled protective coating, Hot Zinc Spray (also known as Zinc Spray, Thermal Zinc Spray, or Arc Spray) is a highly effective alternative to traditional galvanising. Rather than dipping the metal into molten zinc, Hot Zinc Spray involves spraying molten zinc onto the surface using a spray gun. This technique allows for a more even, consistent application of zinc without the need for fettling.
Pros of Hot Zinc Spray:
- No need for fettling: Unlike hot-dip galvanising, the zinc spray provides a smooth finish that doesn’t require extensive grinding or smoothing.
- Even coating: Because the zinc is sprayed in layers, you get a uniform coating, perfect for jobs requiring both corrosion protection and aesthetic appeal.
- Great for powder coating: Zinc-sprayed metal provides an ideal surface for applying a powder coat, ensuring that your topcoat adheres smoothly and lasts longer.
Cons of Hot Zinc Spray:
- Generally higher upfront cost compared to hot-dip galvanising, though this is offset by the elimination of fettling costs.
- Requires specialised equipment and trained technicians to apply correctly.
Many professionals in the coatings industry prefer Hot Zinc Spray for jobs requiring a decorative finish. The smooth surface created by this method means the item is ready for powder coating without the risk of compromising the zinc layer during fettling.
- Electroplating
Electroplating is a process that involves using an electric current to coat a metal object with a thin layer of another metal, typically zinc, chromium, or nickel. While electroplating provides corrosion protection, the coating is usually quite thin and may not be as durable as hot-dip galvanising or Hot Zinc Spray.
Pros of Electroplating:
- Provides a shiny, decorative finish.
- Suitable for small or intricate metal objects.
Cons of Electroplating:
- Less corrosion resistance compared to thicker coatings.
- Not suitable for large-scale industrial applications.
- Anodising
Anodising is a process used primarily for aluminium, in which the metal surface is oxidised to create a corrosion-resistant layer. While anodising is not suitable for steel or iron, it is highly effective for protecting aluminium surfaces in architectural and automotive applications.
Pros of Anodising:
- Provides excellent corrosion resistance for aluminium.
- Can be dyed to produce different colours.
Cons of Anodising:
- Not applicable to steel or iron.
- Limited to aluminium and other non-ferrous metals.
Why Zinc Spray is the Better Choice
When it comes to protecting metal from rust while achieving a smooth, aesthetically pleasing finish, Hot Zinc Spray (HZS) stands out as the superior option. While hot-dip galvanising is effective, the additional cost of fettling to prepare the surface for a topcoat often outweighs the initial savings.
With Hot Zinc Spray, you get the same level of protection without the need for fettling, ensuring that the zinc layer remains intact. This means you maintain the full corrosion resistance while saving time and money.
At NSP Coatings, we exclusively offer Hot Zinc Spray at our factory to ensure the highest quality results. We don’t perform this service on-site, as we believe in maintaining full control over the quality of our work. With our dedicated Quality Assurance (QA) department and in-house transport fleet, we can guarantee that your items will be coated and delivered to the highest standards.
So, if you’re looking for long-lasting, smooth, and effective rust protection, Hot Zinc Spray is the way to go. Contact us today to learn more about how we can help you protect your metal structures from rust.
