Plastification of aluminum

Plastification is the most common method of protection of metals and aluminum today. The whole process takes place in several stages.First, the surface of the aluminum is degreased by immersion in sodium hydroxide. After that, the so-called primer thickness of 0.5 to 1.5 micrometers.

This layer has two basic tasks:
– to increase the bond between aluminum and the organic layer, ie. colors.
– to reduce the so-called filiform corrosion

 

Filiform corrosion occurs due to poorly prepared surface such as wrinkled surface or so-called. orange peel prone to separation from the aluminum surface.
In the next phase, a positively charged color powder is applied. The profiles we plasticize are counter-charged so that the powder and the surface to which the powder is applied firmly adhere.
The pieces thus dusted are fed into special ovens which are heated at a temp. from 180-200 C. The heating results in melting and polymerization of the powder molecules, with a layer of plasticization of 50-70 micrometers thick.
For interior elements, epoxy-based paints are used and for polyester-based exterior elements, which are significantly more resistant to ultraviolet rays.
The choice of plasticizing tone is made according to the RAL chart. Damage to the plasticised surface is successfully remedied by sprays or powders dissolved in a nitro diluent.

Eloxage

Anodizing is a popular term for the process of surface protection of aluminum from corrosion. The process is based on the electrochemical method of anodic oxidation. In the process, aluminum is coated with a single thin oxide layer (about 1 micrometer thick) to protect it from further oxidation. However, this layer thickness is not thick enough and is aesthetically unacceptable, so the aluminum profile undergoes a phase oxidation treatment in which the thickness of the protective layer increases to 12 to 30 micrometers. This process is carried out at special installations in which the tubs are placed, side by side, measuring 6 x 1 m and 2.5 m deep. The tubs are filled with chemicals that sequentially participate in the anodizing process. There is flushing water between each tub. The system is equipped with manipulation cranes to which the profiles are hung.

Anodizing process:
– Mechanical preparation by brushing profiles, devices with circular brushes of thin wires of stainless steel.
– Degreasing in detergents at temp. from 65-75 C for 10 min.
– Degreasing in mineral soda at temp. from 40-60 C for 5 min.
– Neutralization in nitric acid.
– Anodization in sulfuric acid at temp. of 18 C for 50 min.
– Coloring in anodizing fluid – this process is skipped if the anodized color in natural aluminum is required.
– Pore closure, by silencing – cold and warm, about 3 min.

The brushing removes the natural oxides, degreasing and eroding the pores, and anodizing creates a thin layer of aluminum oxide according to the pore configuration. If staining is required, it is done by depositing some metal in the bottom of the pores. The final phase is the silencing that completely closes the pores.
Anodization is carried out in an electrolyte consisting of sulfuric acid dissolved in water. At this stage, a direct current is applied to the aluminum so that the aluminum is a positive electrode and the negative electrode is another suitable metal. Due to the passage of electricity, sulfuric acid begins to decompose. The quality of the anode layer depends on the quality of Al99.5 aluminum (AlMgSi 0.5 alloys, AlMg1, AlMg3) electrolyte concentration, temperature and current strength. Control of these parameters is monitored by computer and pulse rectifier. When the proper layer thickness is reached, the rectifier automatically shuts off and the data is recorded and the quality of the anodized batch determined. The surface layer is transformed into a glassy crystalline coating. The recommended thickness for aluminum profiles that make windows and doors is 20 micrometers, thinner layers are not sufficiently resistant to wear and tear, thicker layers crack when bending profiles. Anodizing tones range from natural aluminum to bronze and black. It is possible to color in gold tones, but it is less persistent. Special procedures make it possible to get shades of blue, red and green, but they are rarely used because of the high cost. Coloring is done with inorganic pigments based on cobalt, manganese. The choice of anodizing tone is made according to the tone of the manufacturer’s chart in 6 shades. Anodized aluminum is highly acid-resistant but alkali-resistant. Particular care should be taken to ensure that no anodized profile remains on the surface, e.g. lime for painting walls because damage is inevitable. Anodizing damage is extremely difficult to remove and can be repaired with special Eloxal sprays. The quality of the anodized layer is tested in authorized laboratories that issue the necessary certificates and certificates.

Decorating aluminum

Metal decorations using the DECORAL method are achieved by sublimating the ink from a special foil into a layer of polyurethane plasticite previously applied to the material in the plastification plant, adhering to all plasticization standards in terms of material pre-treatment, plastics application and powder polymerization. Sublimation of the ink from the foil to the plastic, is carried out in a furnace for decoration, at a temperature of 190-200 ° C. The decorative foil must be completely adhered to the material, which is achieved by vacuum suction of air between the metal and the foil. This allows all the visible surfaces of the material to be decorated at the same time. Decorative patterns mimic different types of wood (oak, beech, walnut, pine, mahogany, teak, etc.), stone (marble, granite), and various abstract patterns. Surveys, laboratory tests and constant inspection guarantee not only the visual plausibility of the samples, but also maximum resistance and weather resistance and mechanical damage to any flat or curved surface. In this regard, DECORAL powder for plastification and foil for decoration have relevant international certificates (QUALICOAT, GSB, RINA, etc.). Metal products processed in this way extend the field of application of metal from construction locksmiths and joinery to the furniture industry, everyday items, etc., and the only limiting element is their own imagination.