Protective Coatings for Steel

Painted Steel

What is it?

Steel is cleaned, primed and painted.

Advantages

• Lowest initial cost
• Large choice of colours
• Easy to touch up if damaged
• Suitable for interior use

Disadvantages

• Lowest corrosion resistance
• Requires periodic maintenance
• Scratches expose bare steel
• Can require repainting every few years in exposed locations

Best Used For

• Indoor steelwork
• Decorative items
• Temporary installations
• Budget-conscious projects

Typical Lifespan

• 3-10 years before significant maintenance depending on environment

Cold Galvanising

What is it?

A zinc-rich paint containing metallic zinc particles applied by brush, roller or spray.

Despite the name, it is not true galvanising.

Advantages

• Better corrosion protection than ordinary paint
• Easy to apply on site
• Useful for repairs
• Lower cost than hot-dip galvanising

Disadvantages

• Not as durable as hot-dip galvanising
• Can be damaged by abrasion
• Lifespan depends heavily on preparation and application quality

Best Used For

• Repairing galvanised steel
• Touching up welds
• Small fabricated items

Typical Lifespan

• 5-15 years

Thermal Spray Galvanising (Metallising)

What is it?

Molten zinc is sprayed onto grit-blasted steel using specialist equipment.

Also known as zinc thermal spraying or metallising.

Advantages

• Excellent corrosion resistance
• Can be applied to large fabricated structures
• No size restrictions from galvanising bath dimensions
• No risk of distortion from immersion in molten zinc
• Ideal for architectural steelwork

Disadvantages

• More expensive than hot-dip galvanising
• Surface preparation is critical
• Specialist process

Best Used For

• Large railings
• Balconies
• Structural steelwork
• Heritage projects
• Coastal environments

Typical Lifespan

• 20-40+ years depending on environment

Hot-Dip Galvanising

What is it?

The completed steelwork is immersed in molten zinc at approximately 450°C.

The zinc forms a metallurgical bond with the steel.

Advantages

• Outstanding corrosion protection
• Very low maintenance
• Protects inside hollow sections
• Excellent value over the life of the product

Disadvantages

• Initial cost higher than paint
• Appearance is industrial rather than decorative
• Large fabrications may exceed bath size limits
• Some thin fabrications can distort if poorly designed

Best Used For

• Railings
• Gates
• Handrails
• Agricultural steelwork
• Public sector projects

Typical Lifespan

• 25-70+ years depending on location

Duplex Coating System (Galvanising + Paint)

The Gold Standard

This combines hot-dip galvanising with a painted or powder-coated finish.

Advantages

• Highest corrosion resistance
• Huge colour choice
• Excellent appearance
• Significantly longer life than either system alone

Typical Lifespan

• Often 40-80+ years

Best Used For

• Premium railings
• Balconies
• Coastal properties
• Commercial developments