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The appearance and surface quality of the aluminium profile are quite satisfactory for many areas of application, even before any surface treatment. Due to its excellent resistance to corrosion, it is rarely necessary to apply surface treatment merely to create protection from corrosion. On the other hand, we do carry out surface treatment of profiles for many other reasons. Surface structure, colour, corrosion resistance, hardness, wear resistance, reflectivity and electrical insulation properties are some of the properties that can be modified. Sapa has extensive knowledge of all types of surface treatment you may want for your product. A few examples of these are anodising, lacquering and decoral.
One of the most common surface-treatment methods, is used to create:
- permanent new appearance
- corrosion resistance
- dirt repellent surface that corresponds to a high standard of hygiene
- decorative surface with durable paint and lustre
- smooth surface
- functional surface, a sliding face or an abrasion-proof surface, for machine parts, for example
- electric insulating surface
- basis for application of glue and paint
The most common form of anodising is natural anodising. Sapa also delivers profiles with oxide layer impregnated with colour pigment. These include pigments with excellent colour fastness, suitable for outdoor use. Anodising produces a decorative, soil-repellent, corrosion-resistant surface. The surface of the metal is transformed into oxide through electrolysis. the process continues until the thickness of the oxide layer is the desired thickness – usually 5–20 µm. The oxide layer can be dyed, as shown here.
There are no restrictions regarding the choice of colour. We use RAL, NCS S and customer-specific dyes. Powder coating is by far the most common method of applying colour to aluminium profiles. The foremost characteristics of powder coating are:
- Minimal risk of running and splattering
- Highly repeatable
- Powder coating withstands high impact abrasion considerably better than wet coating
- Good formability (can be bent after powder coating)
- Suitable for use in open air - high UV radiation resistance and corrosion resistance
Wet coating: Sapa uses various types of paints and can of course offer water-based varnishes.
Sapa has several plants for powder coating, each of them specialized for particular products. The figure illustrates a vertical plant for powder coating. Profiles of up to 7 meters in length hang vertically instead of lying horizontally, which doubles capacity.
Decoral is a variation of powder coating that produces patterned surfaces.
The technique: First, a specially composed powder coating is applied. The pattern is then transferred to the profile. The original, which is often a photographic representation of wood or stone, is copied onto a film that is the bearer of the pigment that creates the pattern. The result is due entirely to the deep penetration of the design. A surface pattern is exposed to considerable stress. The Decoral technique ensures deep penetration. The result is a surface that has all of the properties that characterize traditional powder coating.
Decoral creates: “solid wood,” with the durability of the profile and a surface based on nothing more than ordinary paint. Marble,” with the same density as aluminium. In terms of possible patterns and colours, there are no restrictions.