Surface Finishing for Aluminium...
The anodising process involves immersing the metal in a sulphuric acid bath and then passing an electrical current through the metal. This creates an etching process. Colour is added to the bath, and the etching process seals the colour as a film onto the metal. This film then provides a hard wearing surface. The film’s thickness is an important determinant of how much protection anodising gives.
Film thicknesses available are 12, 20 and 25 microns. Anodising offers a limited range of colours. These are typically black, bronze, and silver, although other colours are available.
You should discuss these with your local Bradnam's branch to understand limits and possible colour variations.
The advantages of anodising are:
- It provides a non reactive surface that resists wear and tear.
- It provides a relatively uniform thickness and depth of finish.
- It will not chip, flake, or peel.
- It offers good resistance to salt air corrosion. We recommend a 25 micron film depth for maximum salt air protection.
The Altus anodising process complies with the Window Association of New Zealand (WANZ) Anodising Standard SFA 3502-03: 2005 written specifically for New Zealand conditions. (See recommended minimum coating thickness table for NZS 3604 Corrosion Zones and Maps below.)
Corrosion Zones NZS 3604
Recommended Minimum Thickness Table NZS 3604
*Anodic oxide coatings produced by the sulphuric acid process that have a thickness in excess of 35 microns may prove difficult to seal to comply with the tests specified in clause 12. Thermal crazing of such anodic oxide coatings may also occur.
NZS 3604 Referenced Corrosion Zones North Island (Normative)
Locality or zone profiles must be referenced when selecting anodic film thickness for areas affected by proximity to coastal exposure. The use of an incorrect option may result in a pitted, stained, and eroded finish within a few years.
Maintenance of Anodising refer to the Care and Maintenance of Aluminium section.
With both anodising and powder coating exposure to ultra violet light may cause some coating colours to exhibit rapid colour degradation. These colours should not be specified for external use. Check with your local Bradnam's branch before specifying.