What preparation is needed for painting aluminum siding on a home in Bathurst NB?

Painting aluminum siding in Bathurst requires more preparation than most other exterior surfaces — specifically thorough cleaning, sanding or deglossing the oxidized and chalky surface, spot-priming any bare metal or corrosion, and applying a bonding primer before your topcoat. Skip any one of these steps and the paint will peel off within a season, particularly in Bathurst's climate which combines NB's standard freeze-thaw cycles with proximity to Chaleur Bay and the associated salt-laden air from the Gulf of St. Lawrence.

Aluminum siding that's more than 10–15 years old will have a layer of oxidation and chalk on the surface — the original paint has broken down from UV and weathering, leaving a chalky, powdery residue. This layer is the enemy of new paint adhesion. Run your hand along the siding: a heavy white residue means significant oxidation that needs to be removed or etched before any new coating goes on. Start with a thorough wash using a TSP (trisodium phosphate) solution or a dedicated aluminum-specific cleaner mixed with water, applied with a scrub brush or soft bristle brush, then rinsed completely. This removes the chalk, dirt, mildew, and oxidation that prevents adhesion. In Bathurst's coastal proximity, mildew growth on aluminum siding — especially on north and east-facing walls — is common. Add a mildewcide to the cleaning solution and scrub all affected areas thoroughly. Don't just rinse mildew off; it needs to be killed or it will grow right through the new paint.

After cleaning, the aluminum surface still needs mechanical or chemical etching to give the new paint a profile to grip. Options:

Light sanding with 80-grit sandpaper scuffs the surface and removes any remaining chalk. Work in the direction of the siding profile. This is the most reliable method but the most labour-intensive for a full house.

Liquid deglosser/etcher applied with a rag or brush after cleaning chemically etches the surface without sanding. Products like Wilbond or Bondex are available at NB hardware stores. Follow manufacturer contact time directions carefully.

After cleaning and etching, spot-prime any areas of bare metal, rust, or corrosion with a rust-inhibiting metal primer ($40–60/gallon). Aluminum itself doesn't rust, but Bathurst homes with older siding often have cut edges, nail holes, or areas where the factory coating is completely gone — these areas oxidize quickly and must be primed before topcoat.

Apply a full coat of acrylic bonding primer over the entire surface before your topcoat. This is the step that most separates a lasting paint job from a failing one on aluminum. A quality exterior bonding primer like Benjamin Moore Fresh Start or Zinsser Bulls Eye 1-2-3 ($40–55/gallon) gives the acrylic topcoat a unified, gripping base across the whole surface.

For the topcoat, use a premium 100% acrylic latex exterior paint in a satin or low-sheen finish at $55–80/gallon. Two full coats over the primed surface. The same colour-darkening caution that applies to vinyl siding applies to aluminum: avoid going dramatically darker than the original colour, as darker colours absorb more heat and can accelerate thermal expansion stress at seams and fasteners.

For a Bathurst bungalow, a professional exterior repaint including full prep, prime, and two topcoats will typically run $4,000–7,000. Given the prep requirements for aluminum, this project leans toward hiring a professional — the prep steps have to be done in the right sequence with the right products, and cutting corners on aluminum almost always results in premature failure.

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