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Aluminium Profiles

Architectural coatings focused on colour, gloss and batch consistency

Aluminium profiles include architectural extrusions, frames and guide rails. Long-term outdoor use requires weatherability, colour retention, adhesion and corrosion resistance.

Veri Coating offers high-durable polyester-HAA textured and smooth powders, as well as standard- and high-durable polyester-TGIC smooth and textured powders, with Gt0-1 adhesion, at least 50% gloss retention after xenon-arc exposure and performance meeting the applicable Qualicoat requirements. TGIC grades offer a cost advantage over HAA grades.

Application notes: Aluminium must receive chromate pretreatment, while surface cleanliness and batch-to-batch colour difference should be strictly controlled; the recommended film thickness is 60-120 um.

Typical Powder Coating Challenges for Aluminium Profiles

Coating Chipping During Cutting and MachiningChipping and exposed aluminium at cut edges require balanced coating toughness and cutting parameters.

Coating Chipping During Cutting and Machining

After aluminium profiles are sawn, punched or milled, the coating at cut edges may chip, lift or locally expose the aluminium. Common causes include inadequate coating toughness, excessive film build, overcure, blunt tooling or excessive feed rate transmitting cutting impact directly into the coating.

Formulation Design

  1. Select a flexible polyester system that balances crosslink density, hardness and bend performance.
  2. Avoid excessive brittle fillers and film build; validate fabrication tolerance separately for low-gloss and textured products.

Process Control

  1. Confirm actual part temperature and avoid overbake that embrittles the coating.
  2. Use sharp tooling and stable clamping, and optimise saw-tooth geometry, rotational speed and feed rate.
  3. Allow the profile to cool fully before machining; where necessary, support the back of the cut and conduct a small trial run first.
Validation Focus
  • Cut-edge chipping rate
  • Bend/cupping
  • Film thickness and cure window
  • Comparison of tooling parameters
Poor Adhesion Caused by Inadequate PretreatmentSheet-like delamination usually indicates loss of control in pretreatment or cure.

Poor Adhesion Caused by Inadequate Pretreatment

Initial appearance may be acceptable after coating, yet flake-like delamination develops after cross-hatch, impact, damp-heat exposure or field service. Typical causes are incomplete degreasing, ineffective oxide removal, a discontinuous conversion coating, contaminated rinses or recontamination after excessive delay between pretreatment and coating.

Formulation Design

  1. Use a polyester system with stable adhesion to aluminium and a cure window matched to the customer's oven conditions.
  2. The powder formulation cannot replace pretreatment; an adhesion-promoting design can reduce variation but cannot compensate for a failed conversion coating.

Process Control

  1. Control concentration, temperature and conductivity for degreasing, etching, conversion treatment and rinse stages.
  2. Prevent contamination from perspiration and oil and avoid prolonged exposure before coating; coat promptly after pretreatment.
  3. Confirm cure from actual part temperature to rule out apparent adhesion loss caused by undercure.
Validation Focus
  • Cross-hatch adhesion
  • Adhesion after boiling water/damp heat
  • Conversion-coating integrity
  • Pretreatment-bath process records
Protective Film Lifting or Adhesive ResidueProtective-film lifting or adhesive residue directly affects finished-product appearance.

Protective Film Lifting or Adhesive Residue

Protective film applied to aluminium profiles may lift locally, detach during transport or leave adhesive residue, pressure marks and gloss variation after removal. Coating surface energy and roughness, migrating additives, application temperature, adhesive type and dwell time all contribute.

Formulation Design

  1. Control surface migration of flow agents, waxes and matting components to maintain predictable surface energy.
  2. Specify protective-film compatibility separately for high-gloss, low-gloss, textured and metallic finishes rather than using one adhesive system for all.

Process Control

  1. Apply film only after the coating has cooled fully and been cleaned, controlling lamination pressure and ambient temperature.
  2. Conduct high- and low-temperature ageing over the actual storage and transport period, and avoid exceeding the film's service life.
  3. Before production, test peel force and adhesive residue on the final colour, gloss and film thickness.
Validation Focus
  • Initial/aged peel force
  • Adhesive residue and pressure marks
  • Gloss change
  • Protective-film compatibility