Metal Cladding Refurbishment & Coating Guide

What Is Metal Cladding Refurbishment?

Metal cladding refurbishment is the process of retaining cladding that remains technically suitable, preparing the existing surface, resolving local defects and applying a compatible protective finish. Spray application is one method used on large profiled surfaces because it can deliver an efficient, consistent coating application. The important technical question is not simply how the coating is applied, but whether the existing steel or aluminium substrate and coating can be prepared to accept the proposed system.

Metal Cladding Recoating & Restoration

Recoating can restore faded or weathered elevations, change the building colour and renew protective performance without unnecessary panel removal. The route depends on substrate type, existing coating condition, corrosion, laps and joints, previous repair history and the requirements of the selected system. For the on-site spray method, see the commercial cladding spraying guide. For plastisol-coated profiled steel, see the plastisol cladding refurbishment guide.

Why It Happens: Deterioration Modes on Metal Cladding

Metal cladding deteriorates through several mechanisms depending on substrate type and environment. On pre-coated steel, UV degradation of the factory-applied coating causes fading and chalking, with eventual adhesion loss. Cut edges corrode progressively from installation onwards. In coastal and industrial environments, atmospheric deposition accelerates both mechanisms. On aluminium, oxidation and anodic degradation cause chalking and loss of reflectivity over time, though aluminium is inherently more corrosion-resistant than steel.

How Is It Assessed?

A metal cladding coating assessment covers: substrate type identification; existing coating condition (chalking extent, adhesion, delamination); cut edge corrosion extent on steel (mapped by linear metreage); fixing condition (corroded heads, missing caps); joint and sealant condition; and total elevation area by system type. This assessment generates the specification and the cost — without it, neither can be produced reliably.

Substrate-Specific Considerations

Pre-Coated Steel (including polyester and plastisol finishes)

Existing coating condition and adhesion must be checked before recoating. Preparation is established from the condition of the existing finish and the selected system requirements. Cut edges and corrosion areas are prepared separately; where exposed prepared steel requires a rust-inhibiting primer, Rocathaan Primer UNI-RW may be specified before the main TopSpray 35 coating stage.

Pre-Coated Steel (PVDF / PVF2)

PVDF / PVF2 finishes should not automatically be treated as equivalent to other factory coatings. Existing finish identification, surface preparation and adhesion requirements should be confirmed against the proposed coating system before work proceeds. Where compatibility is uncertain, testing or manufacturer guidance should form part of the specification process.

Aluminium Cladding

Aluminium must be treated as a distinct substrate when specifying preparation and primer requirements. The proposed coating manufacturer’s compatibility and preparation guidance should be followed rather than assuming that a primer route used on steel is suitable for aluminium. Mixed-substrate buildings may therefore require different preparation or primer stages across the same project.

Galvanised Steel

Galvanised steel also requires substrate-specific consideration. Surface age, contamination, existing weathering and the proposed coating chemistry can affect preparation and primer selection. The appropriate route should be confirmed from the selected system technical guidance rather than relying on a generic metal primer.

When Refurbishment Is Suitable

Metal cladding coating is appropriate where the substrate is structurally sound, existing corrosion is limited to the surface or edge zone (not perforating), and adequate preparation can be achieved to support the specified system. The optimal timing is when the existing coating has degraded visibly (fading, chalking) but has not yet failed in adhesion — preparation requirements are lower and the project cost is minimised.

When Refurbishment Is Not Suitable

Refurbishment is not appropriate where: steel has perforated through corrosion; galvanic corrosion between dissimilar metals is continuing actively and cannot be resolved by coating; or multiple previous coating layers exist with uncertain adhesion that cannot be adequately assessed or prepared.

What Affects Cost?

Substrate type directly affects cost through preparation and primer requirements. Aluminium requires more expensive primer systems. PVDF-coated steel requires more labour-intensive preparation than polyester. Cut edge treatment on steel adds cost per linear metre. Mixed-substrate buildings require more complex material management on site. Beyond substrate-specific costs, the standard project variables apply: area, access method, programme constraints, and geographic location.

What Affects Lifespan?

Long-term performance depends on the condition of the retained substrate, preparation quality, compatibility of primers and topcoats, the applied film build required by the specification, environmental conditions during application, exposure after completion and ongoing maintenance. These factors should be recorded against the project specification where a documented warranty route is required.

Common Mistakes

• Assuming every metal or factory coating can use the same primer and preparation route.
• Skipping compatibility or adhesion checks where the existing coating history is uncertain.
• Failing to prepare and address cut edges or local corrosion before the main coating stage.
• Applying a coating without following the film-build and environmental requirements in the selected system specification.
• Treating water ingress or structural failure as though it can be solved by simply over-coating the surface.