Structural steel is protected from corrosion either by hot-dip galvanising, a zinc coating applied by dipping the steel in molten zinc, or by a paint system. Galvanising is durable and low-maintenance; paint offers colour and flexibility. The right choice depends on the environment, appearance and budget.
Hot-dip galvanising
Galvanising dips the fabricated steel in molten zinc, bonding a tough zinc coating to the whole surface, inside and out. It's specified to BS EN ISO 1461 and is very durable and low-maintenance, which suits external steelwork and harsher environments. The finish is the characteristic matt-grey zinc, though it can be painted over if colour is needed.
Paint systems
A paint system builds corrosion protection in layers, primer, intermediate and topcoat, specified to BS EN ISO 12944 for the building's corrosivity category and design life. Paint gives any colour and a controlled finish, which is why it's common where appearance matters. It typically needs more maintenance over a long life than galvanising.
What drives the choice
- Environment: galvanising is favoured for external or aggressive conditions; paint suits controlled internal environments
- Appearance: paint gives colour and finish control; galvanising gives a metallic grey (paintable if needed)
- Maintenance and life: galvanising is low-maintenance and long-lasting; paint may need recoating
- Cost: depends on tonnage, section and the required durability, not a fixed rule
Combining the two
For the most demanding cases, a duplex system, galvanising plus paint over it, gives both long life and colour. Tell us the environment and the look you need and we'll specify the right protection as part of the quote.
Common questions
- Is galvanising better than painting steel?
- Neither is universally better. Galvanising is more durable and lower-maintenance, which suits external and harsher environments; paint gives colour and finish control for controlled environments. The right choice depends on the environment, appearance and design life.
- What standards cover galvanising and painting?
- Hot-dip galvanising of structural steel is specified to BS EN ISO 1461. Protective paint systems are specified to BS EN ISO 12944, which sets the system by corrosivity category and required durability.
- Can galvanised steel be painted?
- Yes. A duplex system applies paint over galvanising to combine long corrosion life with a chosen colour, used where both durability and appearance matter. The surface is prepared appropriately for paint adhesion.