LB Parkes Technical Data (Click here to go back to Technical Info)

The anodising process
Aluminium components are anodised by placing them in an acid, applying a voltage (the component is made the anode -- hence the term anodising) and artificially growing their own oxide to an even controlled thickness. This anodic thickness is not a surface coating, but is integral with the metal so a cut through it will not allow corrosion to creep between the metal and oxide.

Sulphuric acid anodising
The most common form of anodising is sulphuric acid anodising which offers an anodic film thickness beteen 3 and 25microns, depending on the end use of the components. The lower to middle ranges are ideal for decorative finishes which may be dyed, etched and/or brightened to enhancve the component's appearance. Anodic film thicknesses above 15microns are used for increased durability and external applications, where corrosion reistance and wear are the main criteria.

Chromic acid anodising
Chromic acid anodising produces an anodic film thickness between 3 and 7micorns. It does not have the same wear properties as sulphuric acid, but is more ductile and has frequent aerospace and militatry application, where it also provides a good "key" for paint and bonding. Chromic anodising is opaque in appearance and has the ability to detect cracks in cast components and emphasise grain structure in forgings.

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