Powder coating
A dry powder is sprayed onto the steel with an electrostatic charge and then baked in an oven, where it melts into a hard, even film - typically 60-120 microns in one coat.
- Hard-wearing, even finish with no runs
- Wide range of RAL colours and textures
- Efficient for batches of railings, gates and balustrade panels
- Limited by the size of the oven and the steel must be able to take the heat
- Repairs on site are touch-up paint, which will not exactly match
Wet paint systems
Liquid paint is applied by brush, roller or spray, usually as a primer, an intermediate coat and a topcoat.
- No size limit - suits large structural steel and site work
- Easy to repair and recoat on site
- Systems can be chosen for very aggressive environments
- Needs good surface preparation and drying time between coats
Duplex: galvanising plus a topcoat
For external metalwork, the longest life usually comes from hot-dip galvanising followed by powder coating or paint. The galvanising protects the steel if the topcoat is damaged; the topcoat gives the colour. Powder coating over galvanising needs the right pretreatment to avoid pinholes and poor adhesion.
Which to choose
- Internal stairs and balustrades: powder coat or paint
- External railings, gates and balconies: galvanised plus powder coat (duplex)
- Hidden structural steel: primer, with fire protection if required
- Coastal or very exposed sites: duplex, specified for the environment
Galvanising and powder coating are carried out for us by specialist finishers, and we manage the programme and quality checks. See also galvanising vs painting.