Expert Painters

Painting Colorbond, Galvanised Steel and Metal Fences

30 Oct

Colorbond fences, roller doors, garden sheds, carports, gutters and fascia. Most Melbourne properties have a fair amount of coated or galvanised steel, and it is the surface where DIY paint jobs fail fastest.

They fail for one of two reasons, and both are avoidable.

You can paint Colorbond, but not when it is new

The factory finish on Colorbond is a baked-on coating applied under conditions no site can reproduce. It is extremely durable and it is also very smooth, which is the problem: new Colorbond gives paint almost nothing to grip.

The right time to repaint it is when it has weathered. After years of sun the surface oxidises and goes chalky, and once that chalk is washed back you have a surface with enough key to hold a coating. Signs it is ready:

  • A dull, faded appearance compared with sheltered sections
  • A powdery residue on your hand when you rub it
  • Patchy colour, particularly on north and west elevations
  • Surface rust starting at cut edges, fixings or scratches

If the sheeting is still glossy and the colour is even, painting it is work you do not need to do yet.

Why paint peels off new galvanised steel

This is the classic failure, and it catches tradespeople as well as homeowners.

Fresh galvanised steel has a bright, slick zinc surface that is both too smooth to hold paint and chemically active. Two consequences:

  • Paint applied straight onto new galv has nothing to bond to and sheets off in strips, often within a year
  • An oil-based or alkyd enamel reacts with the zinc in a process called saponification. The zinc effectively turns the binder soapy, and the coating goes gummy and lifts

So on galvanised steel: never use a solvent-based enamel directly, and either let new work weather for six to twelve months, or use an etch primer or a purpose-made water-based galvanised iron primer. Acrylic systems are what belong on this surface.

The preparation that actually matters

Metal is unforgiving because there is no texture to hide behind. Every shortcut shows.

  • Wash thoroughly with sugar soap or a dedicated degreaser. Steel collects road film, exhaust residue and mould in shaded sections
  • Remove all chalk. Run a cloth over it after washing: if it comes away coloured, keep washing. Painting over chalk is painting over a loose layer
  • Rinse properly and let it dry completely
  • Treat rust back to sound, bright metal with a wire brush or abrasive, then a zinc-rich or rust-converting primer. Coating over active rust just hides it while it keeps spreading underneath
  • Scuff glossy areas lightly to create a key
  • Spot-prime every bare patch before the topcoats go on

Our notes on painting metal railings and balustrades cover the rust treatment side in more detail.

Dark colours get hot, and that has consequences

Charcoal and black are the popular choices for fences and garage doors, and they look excellent. Two things to know before committing.

Dark metal in Melbourne summer sun reaches temperatures well above the air temperature, and steel expands and contracts with it. On a long fence run that movement works at the coating constantly, and it is one reason dark finishes on metal need recoating sooner than you might expect.

Dark colours also fade more visibly. A deep charcoal fence that takes full western sun will look noticeably different from the sheltered return within a few years. It is still a legitimate choice, but it is a shorter maintenance cycle than the same fence in a mid-grey.

Where this comes up most

  • Boundary fences, which are usually the largest single area and the most visible from the street
  • Roller and tilt garage doors, where the panel ribs collect dirt and the bottom edge rusts first
  • Garden sheds and carports, often the most neglected steel on a property
  • Gutters and fascia, where the inside of the gutter is almost always worse than the outside. See our guide to painting eaves and fascias
  • Steel posts and framing in pergolas and verandahs
  • Roof sheeting, which is a job of its own and covered in our roof painting guide

If the fence is timber rather than steel, the preparation is a different problem entirely and our fence painting guide covers it.

Near the bay, the cycle is shorter

Salt accelerates everything on metal. On bayside and coastal properties, steel fences, railings and garage doors corrode at cut edges and fixings far faster than the same items a few kilometres inland, and washing salt off before coating is not optional.

If the property is a beach house that sits empty much of the year, the metal is usually the first thing to go. Our guide to getting a holiday home ready covers the wider maintenance pattern.

What we do

  • Colorbond fences, gates, garage doors and sheds
  • Galvanised steel with the correct primer system for its age and condition
  • Rust treatment back to sound metal before any coating
  • Gutters, fascia and steel structural members
  • Colour advice that accounts for heat and fade on metal

We are based in Richmond and work across Melbourne, the bayside suburbs and coastal Victoria.

Call 0404 330 332. If you are unsure whether your fence is ready to be painted, rub it with a dark cloth and tell us what comes off.

đź“Ť Our Service Areas Across Melbourne, the Mornington Peninsula, Surf Coast & Phillip Island

Melbourne & Bayside

Phillip Island & Bass Coast

Surf Coast & Bellarine Peninsula

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