Corrosion Protection of Steel: Galvanising, Coating or Stainless Steel?

Steel rusts – if you let it. For lasting protection there are three main routes: galvanising, coating or opting straight for stainless steel. Which route is the right one depends on the environment, service life and budget. An overview.

Hot-dip galvanising

In hot-dip galvanising to EN ISO 1461, the component is immersed in molten zinc. This creates a firmly adhering zinc layer that acts as a sacrificial anode: even with minor damage, the zinc continues to protect the steel beneath. Hot-dip galvanised steel often lasts for decades outdoors and is low-maintenance – ideal for structural steelwork, railings and outdoor structures.

Coating and painting

Coating systems (primer plus top coat) protect through a barrier against moisture. They can be chosen in any colour and can be matched to corrosivity categories (C1 to C5 to EN ISO 12944). The disadvantage: damage must be repaired, and the service life depends heavily on preparation and coating thickness. Duplex corrosion protection – galvanising plus coating – is often used.

Stainless steel instead of a protective layer

Where protective layers are a nuisance or not durable enough, stainless steel is the solution. 1.4301 is sufficient for many applications; in chloride-containing or aggressive environments, 1.4404, 1.4571 or duplex are advisable. Stainless steel costs more to buy but saves on maintenance and lasts without an additional coating.

Which route for which environment?

A rough rule of thumb: dry interiors – a coating is often sufficient; outdoors and industrial atmospheres – hot-dip galvanising or duplex; wet environments or those loaded with chlorides or chemicals – stainless steel or more highly alloyed materials. We advise you on material selection and supply accordingly.

Frequently Asked Questions

Which lasts longer: galvanising or painting?

Hot-dip galvanising (EN ISO 1461) is usually more durable and lower-maintenance outdoors, because zinc acts as a sacrificial anode and protects even minor damage. Coatings offer colour flexibility but must be repaired if damaged.

When is stainless steel worthwhile instead of corrosion protection?

In wet environments or those loaded with chlorides or chemicals, where protective coatings are not durable enough. Stainless steel costs more to buy but saves on maintenance.

What is duplex corrosion protection?

The combination of hot-dip galvanising and an additional coating. It combines the cathodic protection of the zinc with the barrier effect of the coating and achieves very long protection periods.