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Surface Treatment
Even before surface treatment, the appearance and surface quality of extruded aluminium profiles is perfectly satisfactory for many applications.
Thanks to good corrosion resistance, surface treatment is rarely necessary simply to provide corrosion protection. However, there are many other reasons for treating the surfaces of profiles.
Examples of attributes that can be changed by surface treatment include:
• surface structure
• colour
• corrosion resistance
• hardness
• wear resistance
• reflectivity
• electrical insulation*
The untreated surface
Surfaces do no always need treatment after extrusion. Load-bearing structures and machine parts are examples of products where the surface quality is satisfactory without any treatment |
Anodising
Anodising is an electrochemical process where the oxide film on the aluminium surface is made thicker artificially. The process involves lowering the extrusion into an electrolytic bath where a DC current is connected to the extrusion, which acts as the anode in the circuit. While the natural oxide film is only 0.02 pm, anodising increases the oxide layer to between 5 and 25 µm depending on the product characteristics required. With the anodising process, aluminium’s natural colour (naturally anodised) can be retained or a colour from a wide range of alternatives can be chosen.
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· 5 Micron
is suitable for decorative applications
· 10 Micron
is suitable for internal applications, and outdoor applications where cleaning is very frequent, for example, caravan trim.
· 15 Micron
is recommended for the majority of ordinary architectural requirements.
· 25 Micron
is recommended for heavy duty external permanent architectural applications where little deterioration can be tolerated. |
Anodising |
Powder Coating
Powder coating offers a virtually unlimited choice of colours and is very durable.
In this process, powdered resins along with coloured pigments are applied to metal products using an Electro-static charge. The product is then "baked" in a high temperature oven causing the powder to melt, flow, and then cure, forming a molecular fusion bond. The result is a surface- to- coating bonding unlike any other.
As with solvent based paints thermosetting powders can be formulated to produce high and low gloss decorative coatings , Metallics as well as textured & hammered finishes. The standard colour range gives customers ample choice and if need be, special colour matches and finishes can be made. |
Powder Coating |
Other Methods
Other methods of surface treatment include screen printing and the use of protective foils. Grinding, polishing and barrel processing are examples of mechanical surface treatments. |
Screen Printing
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| TYPE |
TECHNIQUE |
CHARACTERISTICS |
| MECHANICAL |
gringing/brushing
polishing
vibration polishing
highly polished
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fine lines in the direction of grinding. Gives a faint silky matt appearance. Polish the surface and grinding lines partly disappear Matt to shiny surface, suitable for small areas. Gives a mirror finish. |
| CHEMICAL |
Etching
Brightening
Chromating/Phosphating
Altisering
Plating with copper, tin, nickel, silver
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Pre-treament for various types of surface treatment, gives a clean, matt surface.
Gives a mirror finish
Pre-treatment prior coating
Pre-treatment prior coating, strong corrosion resistance
Gives good soldering, conductivity
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| ELECTROCHEMICAL |
Anodising
Electrolytic polishing |
Gives a hard, clear or coloured oxide layer. For decoration or increased surface protection.
Gives a smooth surface with high reflectivity |
| ORGANIC SURFACE COATING |
power coating
screen printing
coating with protective foils |
Gives various degrees of protective and decorative surfaces.
Printing of text, decor patterns etc...
For decoration, protection or other properties |
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