Mill Finish

Our basic louvre finish is mill finish aluminium. Natural aluminium will resist corrosion in a clean atmosphere however the natural process of oxidisation will gradually dull the surface appearance. The oxidised layer is a tough durable film that makes the unit highly resistant to further corrosion.

Whilst on occasion mill may be the preferred finish of choice by far the most popular choice is to paint the louvre to blend or contrast with the building structure or colour design scheme. We offer a full range of coatings in any RAL colour. Specialised colours to the BS range and other special colour ranges are also available.

Polyester Powder

Gilberts provide a full spectrum of colours and gloss levels with many available direct from stock although any other commercially available colour can also be provided to special order.

Our finish of choice is Polyester powder and with its excellent mechanical and colour retention properties powder is recognised as being at the forefront in metal finishing technology providing a higher build in one coat, a tougher finish, and a greater chemical corrosion resistance as compared to liquid paints.

Most of our louvres are polyester powder coated in own powder coating facility providing a high quality finish suitable for standard external weather applications. For more severe environments this finish can be upgraded (applied by an approved external applicator using an alocrom pre-treatment process) to coastal and marine grade level protection.

Our standard finish has been subject to in house longevity tests but has no formal classification. If an extended powder coating warranty is required external finishing will be required by an approved applicator at extra cost.


Our standard powder coat conforms to the following application process and provides typical technical specifications as described however different powder types and gloss levels will cause some variation:

Pre-Treatment: 3 stages with Hot combined degrease /phosphate at 30 – 50°C, cold water rinse and passivation seal. Hot air dry-off oven at 180°C.

Stoving Schedule: 10 mins at 210°C

Dry Film thickness: Normal Film thickness: 70 µm (Min: 40 µm) Max: 150 µm

Visual properties:

  • Gloss (ISO 2813): standard 30 units +/- 5

Mechanical Performance

  • Adhesion Cross hatch (ISO 2409): < Gt1
  • Hardness Buchholz (ISO 2815): > 80
  • Bend (ISO 1519): Mandrel < 6 mm
  • Impact resistance (ISO 6272): direct > 2.5 Nm
  • Impact resistance (ISO 6272): reversed > 2.5Nm

Corrosion Resistance

  •  Weather-O-Meter (Atlas Xenon) 500hrs: > 80% Gloss Retention   
  • Humidity (ISO 6270) 1000 hrs: no change
  • Bend (ISO 1519): no change

Chemical Resistance (25°C)

Polyester powders are resistant to a wide range of chemicals e.g., 10% solutions of lactic, citric, and sulphuric acids, crude oil, sea water, aliphatic hydrocarbons, but are NOT recommended for resistance to ammonia, alkali, or certain solvents such as MEK.

Warranty: Standard powder finish limited warranty is 3 years. 

Extended Warranties – Extended warranties are available up to 30 years subject to powder manufacturers and applicators conditions  

Special Finishes

Where louvres need to blend or match with an anodised surface we can, on occasion, offer a matching anodised finish. Due to the difficulties and complexity of anodising louvres where witness marks, welding marks, joints and extrusion draw lines on the material can affect the appearance, anodising is a specialised process. It requires special purchase of extrusion suppliers anodised material and then special manufacturing handling during assembly. All of these are difficult processes, but not impossible and as such this option is reserved only for larger projects and for louvres that suit the finishing process. Please talk to your sales team advisor about this option.

An easier and less costly option is to select one of the latest anodic type powder coats. These coating have been specially designed to closely match the most common anodised colours. Please contact our sales team for details

Wide Colour Spectrum 

Louvre Design Elements


Multiple blade depths
and border styles tochoose from.


Standard weather performance or high performance. See the difference here.


Standard polyester powder coat in wide range of RAL and BS colours.

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