Railings: galvanised, powder-coated or stainless, how to choose?
The finish decides the service life of an outdoor railing more than the design does. These are the criteria that matter, from a workshop that makes all three.
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Start with the environment, not the price
EN ISO 12944 classifies environments into corrosivity categories: C3 (urban or moderate industrial), C4 (industrial, coastal with low salinity), C5 (heavy industrial or marine). A city-centre balcony is usually C3; a seafront or a heavily chlorinated pool needs more.
Three questions are enough to steer the choice: is the structure near the sea or a road salted in winter? Will it be cleaned regularly? Must it look the same for twenty years?
Hot-dip galvanised steel
Zinc is applied by dipping the finished part. EN ISO 1461 sets an average zinc thickness of about 55 to 85 µm depending on the steel thickness. Zinc protects even where the surface is scratched, and the inside of tubes is treated too.
- Strengths: very good performance in C3 and C4, moderate cost, almost no maintenance.
- Limits: grey metallic look, no colour choice without paint; parts must fit in the bath.
Powder-coated steel
Powder cured in an oven gives an even coat in the full RAL range. For outdoor use, the durable solution is the duplex system: galvanising followed by powder coating. Coating alone on bare steel suits interiors or sheltered areas.
- Strengths: colour choice, neat finish, long protection as a duplex system.
- Limits: a paint chip must be touched up; without zinc underneath, corrosion creeps under the coat.
Stainless steel 304 or 316
Grade 304 (A2) suits interiors and most urban exteriors. Grade 316 (A4), alloyed with molybdenum, is the one to use near the sea, pools or salted roads. Even in 316, regular cleaning prevents surface rust stains.
- Strengths: lasting appearance, no paint, limited maintenance.
- Limits: higher material cost; the grade should be justified by the environment.
Which solution for which project?
Apartment blocks or offices in a city: galvanised + powder-coated gives the best service life for the cost. Seafront, pool, heavily exposed public building: 316 stainless or reinforced duplex. Interior, stairwell: powder-coated steel is enough.
Whatever the finish, dimensional rules stay the same, for example an opening under 11 cm between elements (NF P01-012 in France). Tell us the site address and exposure: we propose the right finish in the quote.
Frequently asked questions.
What is the difference between galvanised and powder-coated?
Galvanising protects steel with a zinc layer; powder coating is a paint that adds colour and extra protection. The two combine into a duplex system.
When should I choose 316 rather than 304 stainless?
Near the sea, pools or roads salted in winter. In other urban cases 304 is generally enough.
Does a galvanised railing have to be painted?
Not necessarily. It can stay grey. If a colour is wanted, powder coating is applied over the zinc.
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