What determines the life of a fence is usually the surface treatment rather than the thickness of the wire. Hot-dip galvanising, PVC coating and electrostatic powder coating protect the same steel wire by three different methods; all three guard against moisture and corrosion, but the way they protect, and the results, differ.
Hot-dip galvanising
In galvanising the wire is dipped into a bath of molten zinc and a zinc layer forms that is metallurgically bonded to the surface. Even when that layer is scratched it protects the surrounding steel cathodically; unlike painted surfaces, rust does not start at the scratch. The finish is matt grey and offers no colour choice.
PVC coating
On PVC coated wire the protection has two layers: the steel inside is galvanised first, then plastic is drawn over it. The outer plastic layer keeps water away from the wire, while the galvanising stays in reserve as a second line of defence wherever the plastic is cut. The result is a surface that leaves no sharp wire ends and is usually produced in a shade of green.
Electrostatic powder coating
Powder coating is given an electrostatic charge and sprayed onto the earthed galvanised surface, then melted onto it in an oven. Using galvanising and paint together is called a duplex coating; the paint protects the zinc from moisture and salt, and if the paint is damaged at a point the zinc beneath steps in and stops the rust from spreading.
Which one for which environment
| Surface treatment | Where it is strong | Its limit |
|---|---|---|
| Hot-dip galvanising | Inland areas, farmland and site perimeter runs | Along the coast the zinc is spent faster in salt-laden air |
| PVC coating | Farm and garden enclosures, where no sharp ends are wanted | Only applied in woven wire mesh form |
| Powder coating | The coastal belt, and facades or estate entrances needing colour matching | On welded mesh panels it is an additional process step |