Surface Finishing

The exposed surface area of an aluminium extrusion is inherently protected by a naturally occurring, transparent layer of aluminium oxide. This barrier layer forms immediately the newly extruded aluminium is exposed to oxygen and is referred to as 'mill' finish. In many instances, this finish may not be suitable for the product's final application. Where additional surface protection and/or colour is required, G.James offers both anodised and powder coated finishing as part of our complete service package.

Anodising is electrochemical ‘conversion’ process that enhances the metallic lustre of aluminium and thickens the surface layer of aluminium oxide. This controlled oxidisation forms a much harder, more corrosion resistant surface finish. For additional protection, G.James implements a ‘hot-seal’ application to the final stages of anodising to prevent any possibility of fading or cracking. See diagram below.

We offer clear anodised and the full-colour spectrum from light bronze through to black, in thicknesses ranging from AA10 micron, up to AA25 micron. Upon request, G.James can also apply a ‘media blast’ process that produces a highly uniform, blemish-free, matte finish.

Anodising Benefits:
• Best finish for resisting corrosion in coastal and high salt environments
• Exhibits a subtle change in appearance when viewed in different light and angles
• Is an integral finish with a high level of colour fastness and surface durability (for resistance against UV degradation, abrasion and heat)
• Does not outgas or deposit stains on the glass when used in high temperature and/or shadow box applications
• Optimal surface coverage
• No risk of adhesion failure

Anodising Characteristics:
• Finishes are subject to colour variation due to differing alloy compositions within the extrusion
• Extrusion die lines can be visible particularly on wider surfaces. These lines can be eliminated prior to anodising with G.James’ media blast process
• While durable and hard to scratch, when damage does occur it is difficult to repair

Powder coating is an electrostatic process where fine paint particles are sprayed onto the surface of pre-treated aluminium. In a similar way that iron filings attract to a magnet, the coloured powder adheres to the aluminium coating surface due to the electrostatic effect. Once the powder is applied, the aluminium is then baked in an oven to achieve a highly durable, painted finish.

G.James undertakes an extensive, chromate conversion pre-treatment process prior to the application of the powder ensuring an improved level of corrosion resistance for the base aluminium surface.


G.James is a Dulux and Akzo Nobel approved applicator offering a selection of standard and high durability grade powders in an extensive range of colours, gloss levels and metallic shades. We are also a licensed applicator of the Effecta process which replicates the colour and appearance of timber grain onto flat-faced aluminium profiles.


Powder Coating Benefits & Characteristics:
• Extensive colour range
• Excludes extrusion die lines
• Small scratch marks can be repaired (touch-up process)
• Powder coating is an efficient and economical process

Anodising-diagram

Comparison Table

Anodising Standard Grade
Powder Coat
Extra High Durability Powder Coat PVF Fluorocarbon
Powder Coat
Composition Electro deposit Thermoset Polyester Thermoset Polyester Fluoro Polymer Resin
Colour Range Clear and light bronze through to black As per manufacturer's colour cards Limited range, made to order colours available Limited range, made to order colours available
Colour Variation Some (dependant on alloy, and angle & intensity of light) Little variation with solid colours. Some variation possible with metallic & bright colours Little variation with solid colours. Some variation possible with metallic & bright colours Little variation with solid colours. Some variation possible with metallic & bright colours
Gloss Range 20 – 90 10 – 80 10 – 80 25 – 60
Scuff / Impact Resistance ¹ Excellent Very good Good ³ Good
Flexibility ² Good Very good Good ³ Good
Years to First Chalk N/A 2 -3 years ⁴ 5+ years 10+ years
Mortar Stain Yes No ⁵ No No
Service Life (Guide Only) 20+ years 10 years 20+ years 30+ years
Coating Thickness (Microns) 10, 15, 20 or 25 60 – 100 60 – 100 30 – 80
Pre-treatment Caustic etch or media blast Chromate Chromate Chromate
Touch Up No Yes Yes Yes
Relevant Standard & Specification AS 1231 AS 3715 AS 3715 AAMA 605.2 AS 3715 AAMA 605.3
Warranty Term of warranty dependent on micron thickness and environment 7 years ⁶ 10 years on request ⁶ 10 years on request ⁶
Applications Housing, residential, commercial & monumental Housing & Residential Residential & commercial buildings Monumental buildings and shading systems

Notes:

¹ Resistance to minor damage during transport (rubbing) and general handling/processing. Excludes scratches.

² Suitability for folding and rolling post-finishing, particularly relevant for aluminium sheet for flashings etc.

³ Electro and Precious colours are not recommended if post finish fabrication (eg. rolling, folding, bending etc.) is required.

⁴ For bright colours (ie. those with high levels of colour pigment) this time is likely to be less. Compliance with the G.James Care & Maintenance Instructions is recommended to reduce the likelihood of chalking.

⁵ Will stain if long-term exposure occurs. Remove and clean any mortar on aluminium surfaces as soon as it is noticed. Refer to the G.James Care & Maintenance Instructions leaflet.

Warranties exceeding these terms, as promoted by Dulux and Interpon (being Suppliers), are issued from the supplier to G.James (being the Applicator) and as such the terms and conditions are not relevant or transferable to the customer.  A copy of the Supplier's warranty (to G.James) is available upon request for the purposes of confirming the application of the powder specified and in no way transfers an extended warranty term to the customer.

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