Colorbond fencing has a design life measured in decades, but the colour does not. After ten to fifteen years in Sydney sun, particularly on a north or west-facing run, the finish fades and the surface starts to chalk.
It can be repainted. Whether it should be, and whether the result lasts, comes down almost entirely to what happens before the first coat.
Understand chalking first
Colorbond is a factory-applied baked-on coating over zinc-aluminium coated steel. Under prolonged UV the resin binder at the very surface degrades and releases the pigment, which is left sitting loose on the face as a fine powder.
Run your hand down an old Colorbond fence and the colour that comes off on your palm is chalk.
This is the central problem for painting. Paint applied over chalk bonds to the chalk. The chalk is not bonded to anything. The coating will look fine for a season and then peel in sheets, and stripping failed paint off profiled steel is considerably worse than the original job.
It is also why washing an old Colorbond fence hard makes the fade permanent and uneven, which we cover in cleaning Colorbond fences, gates and garage doors.
The preparation
This is most of the job and most of the cost.
Wash off all loose chalk. A mild detergent and a soft brush, working panel by panel, then a thorough rinse. The test is simple: wipe a dry cloth over the surface after it dries. If colour still transfers, keep going. Repeat until the cloth stays clean.
Pressure alone will not do this well. It drives chalk around and burnishes the surface unevenly. Mechanical agitation with a brush is what actually lifts it.
Deal with rust. Colorbond rusts at cut edges, at fixings and anywhere the coating has been damaged. Wire brush or sand back to sound metal. On a coastal fence, check the bottom rail and the post bases carefully — that is where it starts.
Degrease. Especially near a driveway or a barbecue area.
Scuff the surface. A light abrasive pad dulls the remaining factory sheen and gives the primer something to key into. Not aggressive sanding — just taking the gloss off.
Let it dry completely. Including the lap joints, where water sits.
Primer and paint
Use an etch primer or a dedicated metal primer suitable for pre-painted steel. This is not optional on a chalked surface, and it is where cut-price jobs cut.
For the topcoat, a quality exterior acrylic rated for metal. Two coats. Solvent-based enamels can be used but are less flexible, and a fence panel moves and expands more than most people expect.
Spray gives the best finish on profiled sheet. Rolling works but leaves texture in the valleys, and brushing a full fence is slow and shows.
Colour matters more than on a wall. A dark colour on a north-facing steel fence gets genuinely hot, which stresses the coating and accelerates fade. Going darker than the original is the commonest way to shorten the life of the repaint.
Conditions
Steel heats fast. Painting a fence in direct Sydney summer sun means the paint flashes off before it levels, and you get lap marks and poor adhesion.
Work in the shade, or follow the shade around the fence through the day. Early morning on a humid day is also a problem — condensation on steel is invisible and ruins adhesion.
Check the product’s temperature and humidity window and take it seriously.
The coastal question
On a fence within a few hundred metres of surf, think about this differently.
Salt deposits on the surface will compromise coating adhesion even after a visual clean, so the wash has to be thorough and properly rinsed with fresh water. And the underlying zinc-aluminium coating is what is actually protecting the steel — if that has been breached at the base of the posts or along the bottom rail, paint is cosmetic and the fence has a limited remaining life regardless.
Our piece on what coastal exposure does to a home’s exterior covers the broader picture.
When not to repaint
If there is significant rust through the sheet, repainting is money spent on a fence that needs replacing.
If the fence is only faded rather than chalked — colour dulled but nothing transferring to your hand — a proper clean may get you most of the way back for a fraction of the cost and without starting a repaint cycle. Worth trying first.
And it is worth knowing that painting Colorbond ends the factory finish. From then on it is a painted fence on a repaint cycle, typically seven to ten years. That is a reasonable trade if the colour has genuinely gone. It is a bad trade if it has not.
Shared fences
A boundary fence in NSW is generally a shared asset under the Dividing Fences Act, and repainting it is worth a conversation with the neighbour before you start, particularly if you are changing the colour. Cheaper than the alternative.
The cleaning side
We do the wash and chalk removal rather than the painting, and on a long fence run that preparation is the bulk of the labour. See fence cleaning.
If after a proper clean the fence looks acceptable, we will say so, and you can skip the repaint entirely.
