What is Galvanising and is it right for you?

Galvanising is a process of applying a protective zinc coating to steel or iron to prevent rust and corrosion. The zinc layer acts as a barrier between the metal and the environment, providing protection in two ways:

1. Barrier Protection: The zinc coating shields the underlying metal from moisture, oxygen, and other corrosive elements.

2. Cathodic Protection: Even if the coating gets scratched or damaged, zinc sacrifices itself by corroding in place of the steel, protecting the base metal underneath.

Types of Galvanising

1. Hot-Dip Galvanising: The steel or iron is immersed in molten zinc, forming a thick, durable coating. This is the most common method.

2. Electro-Galvanising: A thinner zinc coating is applied through an electroplating process, providing a smoother finish but less durability.

3. Thermal Spraying: Zinc is sprayed onto the metal surface using heat.

4. Mechanical Plating: Zinc particles are mechanically bonded to the surface by tumbling the metal with zinc powder and other chemicals.

The lifespan of galvanised steel

The lifespan of galvanised coatings depends on environmental conditions and the thickness of the zinc layer. In mild, rural environments with low pollution and moisture exposure, galvanised steel can provide protection against rust for 50 years or more. In urban or industrial settings, where exposure to pollutants is higher, the lifespan typically ranges from 20 to 30 years. In marine environments or areas with high humidity and salt exposure, the protective layer may last 10 to 20 years due to the more aggressive corrosion processes. Regular inspections and maintenance can help maximise the lifespan of galvanised components in harsher conditions.

What about my old rusty gates, can they be galvanised?

Yes, you can galvanise old steel, such as old gates, but it requires proper preparation to ensure the process is effective. Galvanising involves applying a zinc coating, which needs a clean surface to bond properly. Here’s how it typically works for older steel items:

Preparation Steps for Galvanising Old Steel:

1. Inspection for Structural Integrity. The steel should be inspected for any significant rust damage or weakened areas. Severely corroded sections may need repairs or replacement before galvanising.

2. Rust and Paint Removal. All existing rust, paint, and debris must be removed. This is typically done through abrasive blasting or chemical stripping to restore the steel to a clean surface.

3. Degreasing and Cleaning. The steel is cleaned to remove oils, grease, and contaminants. This ensures proper adhesion of the zinc coating.

4. Pickling. The steel is treated with an acid solution to remove any remaining mill scale, rust, or surface impurities.

5. Galvanising. Once the steel is fully cleaned and prepared, it can be hot-dip galvanised by immersing it in molten zinc.

Challenges with Galvanising Old Steel:

• Surface Condition: Severely pitted or corroded steel may not galvanise well, as the zinc may not coat deeply corroded areas uniformly.

• Cost: The cleaning and preparation of old steel can be labour-intensive and costly.

• Distortion: If the steel is thin or has been repaired, there’s a risk of warping during the hot-dip process due to the high temperature of molten zinc.

What about my old rusty gates, can I get them galvanised?

Sometimes galvanising old steel isn’t feasible, other protective methods like zinc-rich paint, cold galvanising sprays, or powder coating may be considered. These are less durable than hot-dip galvanising but can be effective for restoring old gates.

Either way, by addressing these challenges with proper preparation, it’s entirely possible to protect old steel and give it a renewed, long-lasting protective layer.

If you're interested in galvanising services or other protective coatings we offer, contact us here.

Some gates just come back from the galvanisers.