Aluminium

Although aluminium is the third most abundant element on earth after oxygen and silicon, its industrial-scale production only began in 1886 with the introduction of the electrolysis method.

Like other widely used metals such as iron, lead and tin, aluminium is found in nature in compound form. The first person to separate and obtain aluminium from its oxide compound was Sir Humphrey Davy in 1807. Later, Hans Christian Oersted, Friedrich Wöhler and Henri Sainte-Claire Deville brought innovations to the production of aluminium.

Industrial-scale production of aluminium began in 1886 with the electrolysis method developed independently by Charles Martin Hall in the USA and Paul T. Héroult in France. As this method is still used today, 1886 is regarded as the founding year of the aluminium industry.

With Werner von Siemens's discovery of the dynamo in 1886 and K. J. Bayer's discovery of the Bayer Process (Bayer Method) in 1892, which made it possible to obtain alumina from bauxite, the industrial-scale production of aluminium became much easier and this youngest metal became the second most widely used metal in the world after iron and steel.

When the properties of price, durability and lightness are considered together, aluminium emerges as the most optimal material for many sectors. Aluminium is a material that can be 100% recycled without losing any of its original properties. 75% of the aluminium ever produced worldwide is still in use, and the recovery of aluminium uses only 5% of the energy required for primary aluminium production. Considered together, this puts aluminium at the forefront for its sustainability and environmental friendliness.

Aluminium is highly resistant to weather conditions and corrosion. Aluminium has a natural anti-corrosion coating. In addition, the desired surface appearance can be achieved through anodising (controlled oxidation).

Aluminium profiles are not only light and durable but also offer architects highly customisable design possibilities thanks to their very high application precision. In other words, aluminium profiles can be produced to very precise dimensions.

Aluminium has high chemical resistance by nature, meaning it is easy to maintain, and compared with copper it is lighter and cheaper.

Aluminium sheet and extruded building materials used in the construction sector account for a significant share of total aluminium consumption.

Although the physical and chemical properties of aluminium are given below, using only these values without describing the chemical composition, production process and hardening stages of the aluminium — which generally appears as an alloy — would be misleading.

Basic properties Atomic number 13 Element series Metals Group, period, block 13, 3, p Appearance: Silvery Atomic weight 26.9815386(8) g/mol Electron configuration 1s2 2s2 2p6 3s2 3p1 Electrons per energy level 2, 8, 3	Atomic properties Crystal structure Face-centred cubic Oxidation states (3+) (amphoteric oxide) Electronegativity 1.61 Pauling scale Ionisation energy 577.5 kJ/mol
Physical properties State of matter solid Density 2.70 g/cm³ Density in liquid state 2.375 g/cm³ Melting point 660.32 °C Boiling point 2519 °C Heat of fusion 10.71 kJ/mol Heat of vaporisation 294.0 kJ/mol Heat capacity 24.2 J/(mol·K)	Other properties Electrical resistivity 26.50 nΩ·m (at 20 °C) Thermal conductivity 237 W/(m·K) Thermal expansion 23.1 µm/(m·K) (at 25 °C) Speed of sound 5000 m/s (at 20 °C) Mohs hardness 2.75 Vickers hardness 167 MPa Brinell hardness 245 MPa

For over a century, aluminium has been produced by the same method worldwide. Aluminium production takes place in two stages. In the first stage, "Alumina (Aluminium Oxide)" is obtained from bauxite ore by the Bayer Method. In the second stage, aluminium is obtained from alumina by electrolysis. Alumina plants are usually built next to bauxite mines. The bauxite ore extracted from the mine is treated with a caustic soda solution to produce aluminium hydroxide. The insoluble residues produced by this process (red mud) are separated, and "alumina" is obtained by calcining the aluminium hydroxide.

The next stage is the conversion of "alumina" into "aluminium". Alumina, which appears as a white powder, is placed into special vessels called cells where the electrolysis process will take place. The aim here is to separate aluminium from oxygen. A direct current of 4–5 volts is applied for the electrolysis process. The process is completed by collecting the aluminium that accumulates at the bottom.

In general, 2 units of alumina are obtained from 4 units of bauxite by weight, and 1 unit of aluminium is obtained from 2 units of alumina.

The energy consumption of 42,000 kWh per tonne of primary aluminium produced in the early days has now fallen to an average of 16,500 kWh. With the latest technology, this figure is 13,000 kWh/t.

Primary aluminium production

Aluminium produced by the processes described above is defined as "Primary Aluminium".

Secondary aluminium production

Because the recovery of aluminium is more economical than obtaining it from ore, and thanks to its 100% recyclability, recovery from scrap has gained importance over time. This method is called "Secondary Aluminium" production.

Secondary aluminium production is more economical because it requires 5–8% less energy than primary aluminium production.

Aluminium is converted into various semi-finished products and finished products through extrusion, rolling and casting processes.

Flat Products

Flat products such as plate, sheet and foil are obtained from aluminium by hot and cold rolling.

Extruded Products

Aluminium profiles, bars, tubes, flat bars and wire rod in various cross-sections are obtained by the extrusion method.

Aluminium is a metal that is very well suited to extrusion. This allows many products to be produced economically in the shapes and dimensions required for their intended use, without the need for any further forming process.

Cast Products

Parts of various sizes and shapes are produced from aluminium by permanent-mould, die or sand casting methods.

Aluminium Conductors

Aluminium, being lighter than copper, offers a major advantage in transmitting electrical energy. For this reason, power transmission lines are now made of aluminium. Aluminium conductors are produced by a three-stage process: obtaining wire rod by continuous casting, drawing the wire rod into wire on a rolling mill, and stranding the wires.

Aluminium and Construction

The construction sector uses 1.2 million tonnes of aluminium per year in Europe, 1.05 million tonnes in the USA, and 915,000 tonnes in Japan (worldwide use of aluminium for architectural purposes in 2000).

Aluminium is used in large quantities for roof and façade cladding of buildings, in doors and windows, stairs, roof frameworks, scaffolding and greenhouse construction.

Alongside its strength, aluminium's decorative appearance is in a sense made permanent through anodising (anodic oxidation) coating. Whether through natural or coloured anodising, or through lacquer coating (electrostatic powder or liquid painting), aluminium offers architects and engineers a rich range of choices in the construction sector. In the construction sector, aluminium extrusion, flat products and cast products are used in the manufacture of door/window frames, façade/roof cladding and accessories.

In addition, aluminium is also widely used in the packaging, transportation and conductor sectors.

A homogeneous mixture formed by combining a metallic element with at least one other element (metal or non-metal) is called an alloy. Aluminium is alloyed — that is, not used in pure form — preferably with elements such as copper, manganese, silicon, magnesium and zinc, in order to acquire certain properties. For example, the tensile strength of pure aluminium is 49 MPa, whereas when alloyed it can reach up to 700 MPa. When classifying aluminium alloys chemically, a 4-digit (XXXX) notation is used. Aluminium alloys can be divided into 2 main groups: wrought and cast alloys.

Wrought alloys

• 1XXX series 99% < aluminium
• 2XXX series main component Cu
• 3XXX series main component Mn
• 4XXX series main component Si
• 5XXX series main component Mg
• 6XXX series main components Mg and Si
• 7XXX series main component Zn
• 8XXX series special alloys

as classified. The 2XXX, 6XXX, 7XXX and 8XXX series can be heat-treated.

Zinc (Zn) gives the alloy strength and hardness.

Copper (Cu) gives heat-treatability, strength and hardness, but reduces corrosion resistance.

Manganese (Mn) increases yield and tensile strength and provides corrosion resistance.

Silicon (Si), when used with magnesium, gives heat-treatability and improves corrosion resistance.

Magnesium (Mg) gives strength and hardness and improves corrosion resistance and weldability.

Aluminium Alloys Used for the Extrusion Process

Extrusion is the process suited to producing constant-cross-section shapes in long lengths — such as profiles, tubes, bars and flat bars, including the aluminium profiles used in architectural aluminium systems. The alloys used for manufacturing aluminium profiles by extrusion are from the wrought-alloy group.

6XXX series alloys

Profiles produced for architectural purposes are generally manufactured from 6XXX alloys by extrusion. As stated above, AA 6XXX series alloys contain magnesium (Mg) and silicon (Si). Together with Mg and Si, the ratios of other impurities (such as Fe, Cu, Mn, Zn) give the alloys different properties. For example, 6XXX alloys with an iron (Fe) content of 0.20% or lower are better suited to producing a bright surface. For a matt surface, higher iron content is preferred.

Among the 6XXX series (AlMgSi) alloys, the most widely used in the architectural / construction sector are 6060 and 6063 (EN and new TS notation) and AlMgSi0.5 (DIN and old TS notation). Their chemical compositions are generally the same, with differences only in upper and lower limits.

6005 / 6005A

Compared with 6063, EN AW / AA 6005 and 6005A alloys are harder and have stronger mechanical properties, but are more expensive and more difficult to extrude, which complicates or prevents the production of complex geometries.

Profiles made from 6005A alloy can be anodised for protective purposes, but the surface quality makes it difficult to achieve a decorative appearance.

In terms of plastic forming ability, this alloy is not as successful as 6063.

6060

This is the alloy suitable for an optimum surface quality after surface treatment, in cases where strength is not the most important criterion. It is preferred for decorative-priority applications such as furniture profiles.

6063

Application areas: architectural sections in window, door and façade systems, furnishings, frame systems, lighting, treads, rails, electronic modules, electric motor housings, fasteners, heat sinks, radiators, pneumatics, irrigation, furniture profiles. It can be said that 6063 is slightly harder than 6060 but more difficult to extrude.

Characteristic properties: high corrosion resistance, very good weldability, high fatigue strength, cold-formable, can be formed into complex geometries.

6082

Compared with 6005, impact toughness is slightly better, but suitability for decorative anodising is slightly worse. Its other properties are similar to those of the 6005 and 6005A alloys.

Compared with 6063, EN AW / AA 6082 is harder and has stronger mechanical properties, but is more expensive and more difficult to extrude, which complicates or prevents the production of complex geometries.

Profiles made from 6082 alloy can be anodised for protective purposes, but the surface quality makes it difficult to achieve a decorative appearance.

In terms of plastic forming ability, this alloy is not as successful as 6063.

Application areas: heavy structures in railway wagons, truck side rails, shipbuilding, bridges, bicycles, boilers, platforms, flanges, hydraulic parts, pylons, ship masts, awning tubes, rivets.

Characteristic properties: high corrosion resistance, very good weldability, suitable for machine building, excellent cold-forming ability when stabilised after T4 heat treatment, medium fatigue strength, not suitable for complex parts.

6101

6101 alloy may be suitable for profiles requiring high electrical conductivity together with high hardness. 1XXX series alloys also have high electrical conductivity, but 6101 has better machinability, and its tensile strength is also higher than that of the 1XXX series.

6463

This is the most suitable alloy for obtaining bright aluminium.

Other Alloys

1XXX

Alloys in this series are not suitable for heat treatment. Their corrosion resistance is good. Although relatively soft and weak, they are preferred for their high thermal and electrical conductivity. Their electrical conductivity makes them preferred in the electrical industry, and their high thermal conductivity in the HVACR industry. Another alloy with good electrical conductivity, 6101, is better in terms of machining and also has higher tensile strength than the 1XXX series.

2024

Application areas: aerospace industry, general engineering applications, military equipment, parts requiring high hardness and machinability, truck wheels, automotive.

Characteristic properties: heat-treatable. High fatigue strength; corrosion properties are improved by coating.

5005

Application areas: external façade applications in construction, corrugated roof sheets, marine and offshore applications, food and chemical equipment, the advertising sector, road signs, parts requiring anodising, the packaging sector, cooling and heating equipment, pipe and tube manufacture.

Characteristic properties: very good resistance to atmospheric corrosion. Very good weldability. Very suitable for decorative anodising. A medium-strength alloy.

7XXX

Different companies prefer different 7XXX alloys when listing their alloy options — 7075, 7108, 7005, etc. All of them can be described as alloys with high hardness and durability. Their fatigue strength is high. Their weldability is good and there is little drop in hardness in heat-affected zones. They are recommended for adhesives, rivets and screws. Use with a protective coating is recommended in outdoor environments because their corrosion resistance is not as good as that of the 6XXX series. They are also not as successful as the 6XXX series for forming.

Application areas: components requiring high strength in the military and aerospace industries, rubber and plastic moulds, ski poles, machine parts requiring high strength, the automotive industry, rivets, nuclear applications.

Characteristic properties: high hardness can be achieved more easily than with 7010.

Heat Treatment of Aluminium Alloys

Different heat treatments can be applied to aluminium alloys. The types of heat treatment for aluminium alloys are as follows:

O: Annealed, F: As-manufactured, H: Strain-hardened, T: Heat-treated

T1: Cooled from a hot-forming process and naturally aged.

T2: Cooled from a hot-forming process, cold-worked and naturally aged.

T3: Solution heat-treated, cold-worked and naturally aged.

T4: Solution heat-treated and naturally aged.

T5: Cooled from a hot-forming process and artificially aged.

T6: Solution heat-treated and artificially aged.

T7: Solution heat-treated and overaged/stabilised.

T8: Solution heat-treated, cold-worked and artificially aged.

T9: Solution heat-treated, artificially aged and cold-worked.

T10: Cooled from a hot-forming process, cold-worked and artificially aged.

The applied heat treatment is denoted by writing the Tx symbols (T1, T2, etc.) next to the alloy number to identify the material.

The hardening of an aluminium alloy at room temperature — in which the alloying elements in the solid solution come out of solution and precipitate, causing the material to harden — is called "natural ageing".

Aluminium profiles used in aluminium window and façade systems are held at 180 °C for 5 hours in thermal (heat-treatment) furnaces after extrusion. This process is called "artificial ageing". In this way, hardness values much higher than those achievable by natural ageing can be reached.

Related standard: TS EN 515 (Aluminium and aluminium alloys — Temper designations for wrought products)

Raw aluminium profiles are produced by shaping aluminium billets (cylindrical aluminium alloy raw material) using the aluminium extrusion method, cooling them on the run-out table, cutting them to standard or special lengths, and bringing them to the required hardness value through artificial ageing. Raw profiles are produced as standard in 6-metre lengths, but different lengths can also be ordered by agreement with the manufacturer. Some computer programs help minimise waste by optimising cutting lengths. This means less waste for the fabricator. Through the thermal-break fitting process, plastic profiles called thermal-insulation breaks are inserted and crimped between 2 aluminium profiles. This forms a thermally insulated aluminium profile.

Aluminium profiles that have been heat-treated but not subjected to any surface treatment are called raw profiles (mill finished). On raw profiles there is a 1–2 micron oxide layer that forms by the nature of aluminium. This layer provides some protection against oxidation. However, in order to be aesthetically pleasing and to be protected against corrosion, these raw aluminium profiles are subjected to one of the surface treatments. These surface treatments can be anodising, electrostatic powder coating or wood-effect coating.

Through extrusion, aluminium can be produced in any required length with very precise dimensions to a geometry defined in the plane of the page (2 axes). With this method, aluminium profiles can be produced for many sectors such as architecture, automotive, shipbuilding, aerospace, electrical, machinery, chemicals and food.

Aluminium Extrusion Press

The aluminium extrusion process is carried out with aluminium extrusion presses. As the tonnage of the press increases, so do the billet diameters, and therefore the maximum die sizes that can be pressed also increase, allowing dies with more cavities to be made.

Aluminium Extrusion Process

• The steel die, designed to match the required aluminium profile shape, is heated and placed in the extrusion press.
• It is then pushed into the cylindrical aluminium extrusion press container, which has also been preheated.
• The extrusion press uses a ram to push the billet against the die.
• Once the aluminium billet takes the shape of the die, it is now called an aluminium profile.
• The profile is cooled, then stretched and cut to the required length.
• An artificial ageing (thermal) process is applied so that architectural aluminium profiles acquire the required mechanical properties.

The cross-section of an aluminium profile produced by extrusion is constant along the length of the profile. To produce profiles in the required cross-section, steel aluminium extrusion dies are manufactured and stored for repeated use. In an aluminium extrusion factory that produces aluminium frame profiles, given that the frame, intermediate transom, sash and bead profiles come in different wall thicknesses, depths and widths, hundreds of profiles are produced, and accordingly at least as many steel extrusion dies are required.

Extrusion presses are classified according to the press force they apply. Large presses are more suitable for pressing large profiles, and small presses are more suitable for small profiles. Although in theory small profiles can also be pressed on large presses by increasing the number of cavities (the number of profiles produced from a single die), in practice this is not always possible due to the difficulty of controlling shape tolerances.

• TS-EN Standards Relating to Aluminium Alloys
• TS EN 12020-1 Aluminium and aluminium alloys — Precision profiles in alloys EN AW-6060 and EN AW-6063 — Part 1: Technical inspection and delivery conditions
• TS EN 12020-2 Aluminium and aluminium alloys — Precision profiles in alloys EN AW-6060 and EN AW-6063 — Part 2: Tolerances on dimensions and form
• TS EN 13981-1 Aluminium and aluminium alloys — Products for structural railway applications — Technical conditions for inspection and delivery — Part 1: Extruded products
• TS EN 755-1 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 1: Technical conditions for inspection and delivery
• TS EN 755-2 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 2: Mechanical properties
• TS EN 755-3 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 3: Round bars, tolerances on dimensions and form
• TS EN 755-4 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 4: Square bars, tolerances on dimensions and form
• TS EN 755-5 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 5: Rectangular bars, tolerances on dimensions and form
• TS EN 755-6 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 6: Hexagonal bars, tolerances on dimensions and form
• TS EN 755-7 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 7: Seamless tubes, tolerances on dimensions and form
• TS EN 755-8 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 8: Porthole tubes, tolerances on dimensions and form
• TS EN 755-9 Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 9: Profiles, tolerances on dimensions and form
• TS EN 13957 Aluminium and aluminium alloys — Extruded round coiled tube — For general applications — Specifications

Aluminium profiles can be produced not only in a wide variety of shapes but also with a wide variety of surface appearances. As well as giving the product the desired aesthetic appearance, aluminium surface treatments also help increase the profiles' resistance to corrosion and abrasion. In general, we can speak of 3 different surface treatments. You can find information about the types of surface treatment via the related links:

The electrochemical surface-treatment process by which aluminium can be given brown and black tones — and even copper and gold colours — without disturbing its metallic appearance is called "anodising". The pre-treatments applied before the anodising process determine the texture of the metallic appearance and whether it is matt or glossy.

Qualanod certificate

From a production perspective, the first requirement is that anodised aluminium profiles must be produced by manufacturers holding the Qualanod quality certificate.

Anodising pre-treatments

The anodising pre-treatments are, in order, mechanical and chemical pre-treatments, and vary according to the desired surface appearance. If a matt appearance is required, a satinising mechanical pre-treatment is applied. In this method, the extrusion lines are eliminated using stainless-steel brushes, and a characteristic satin surface texture created by the brushes is imparted to the profile. If a glossy appearance is required, a polishing pre-treatment is applied. In this, the profiles are polished using a liquid or solid polish.

DIN 17611 sets out standard designations for anodising pre-treatments and colour choices. According to this standard, E0, E1, E2, E3, E4, E5 and E6 designate pre-treatments and EV1, EV2, EV3 and EV6 designate colour choices, so when we say E6EV1 we mean EV1 (natural colour) is required after the E6 (chemical matting) pre-treatment. The European Association of Anodisers (EURAS) uses the designations C0, C31, C32, C33, C34 and C35.

Pre-treatment designations
E0 degreasing and oxidation
E1 sanding
E2 brushing
E3 mechanical polishing
E4 sanding + brushing
E5 sanding + polishing
E6 chemical matting

Colour designations
EV1 natural colour
EV2 silver
EV3 gold yellow
EV6 black

EURAS colour designations
C0 natural anodising colour
C31 very light bronze
C32 light bronze
C33 bronze
C34 dark bronze
C35 black
C36

Accordingly, the E0 EV1 anodising surface treatment can essentially be used to protect aluminium against corrosion. In addition to a decorative appearance, anodising may also be required on the aluminium surfaces where the glass will bear on the aluminium in curtain-wall applications.

The anodising process

The anodising process is an electrochemical one. The aluminium profile is immersed as the anode in an acidic electrolyte. A direct current is passed between the cathodes in the bath and the profiles acting as the anode, and by this method a protective oxide layer of aluminium oxide between 5 and 30 microns thick is formed on the surface of the aluminium profile.

How many microns should the anodised layer be?

The chart below can be used for this. It can be seen that an anodised coating of 25 µm (microns, micrometres) erodes by 0.07 to 0.50 µm per year depending on weather conditions.

Anodised layer wear (micrometres – years)

In summary, an anodised layer 25 µm thick has a service life of around 40 years, and around 30 years in harsh weather conditions.

According to DIN 17611, anodised profiles used for architectural purposes are required to have a 20-micrometre anodised layer. According to the British Standard (BS), 25 micrometres is required.

The surface of aluminium profiles can be coated with powder paint to give the required colour. Standard RAL colours, colour mixes, special colours, plus surface effects such as velvet, textured, etc., and even surface properties such as self-cleaning can all be achieved with powder coating. The breadth of this range is an advantage compared with anodising.

Qualicoat certificate

From a production perspective, the first thing we should look for is that powder-coated aluminium profiles have been produced by manufacturers holding the Qualicoat quality certificate. There are over 500 products and over 400 licensed coating plants.

What is powder coating?

It is also called electrostatic powder painting, powder painting or powder coating.

Powder coating is a type of coating applied as a free-flowing dry powder. The coating is applied electrostatically and is then cured under heat to allow it to flow and form a thin film.

There are two main categories of powder paint: thermoset and thermoplastic polymers. The most commonly used polymers are polyester, polyurethane, polyester-epoxy, straight epoxy and acrylics. The components of the powder-coating process can vary slightly from one manufacturer to another.

Powder paint is used to form a hard, continuous coating on the aluminium surface that protects the metal against corrosion and provides a long-lasting attractive appearance when exposed to various weather conditions. Powder paint is mainly used widely for household appliances, aluminium extruded products (window profiles, other architectural profiles, etc.), automotive and industrial applications.

Properties of Powder Paint

Because powder paint does not have a liquid carrier, it can produce thicker coatings than conventional liquid coatings. The coating process emits few volatile organic compounds (VOCs). Several powder colours can be cured together, allowing colours to be mixed within a single layer and creating special effects. Thick coatings, which allow smooth, textureless finishes, are relatively easy to apply; thin coatings are not easy to apply.

One of the most important advantages of powder paint is that excess powder that does not adhere to the product during the powder-coating process can be recycled.

Many of the perceived advantages (hardness, gloss, etc.) of powder coating over liquid coating (with the exception of PVDF) are in fact characteristics of polymers.

The powder-coating process

1. Preparation and pre-treatment

Before the powder-coating process, the aluminium is cleaned by various chemical and mechanical methods. The choice of method depends on the material and size of the part to be powder-coated, as well as the performance requirements of the finished product.

The pre-treatment process both cleans the metal and improves the adhesion of the powder to the metal. Chemical pre-treatments usually take place in several stages and consist of degreasing, etching, de-smutting, various rinses and chromating.

Recently, processes have been developed that avoid the use of chromates. Titanium and zirconium chemicals and silanes also show similar performance for corrosion resistance and improving powder adhesion.

Another method for preparing the surface before coating is known as abrasive blasting or shot-blasting.

2. Powder paint application process

The most common way to apply powder paint to metal objects is to spray the powder using an electrostatic gun. The gun gives the powder a positive electrical charge. The powder is then sprayed, accelerated by mechanical or compressed air, towards the earthed part to be painted. The object coated with powder is then heated so that the powder melts and spreads as a uniform film over the painted part.

3. Curing

When a thermoset powder is exposed to a high temperature, it melts, flows and then reacts chemically to form a higher molecular weight polymer with a network structure.

This curing process can take place at a given temperature for a given time. Powders are normally cured at 200 °C (390 °F) for 10 minutes.

Applications for powder-coated aluminium

Powder-coated aluminium is a building material that finds applications in a wide range of construction projects. The powder paint on the aluminium helps to enhance the metal's corrosion resistance. This makes the material ideal for outdoor use.

Architectural powder coating offers a wide range of appearance options — starting with white and including countless RAL colours and other special colours, in the desired effects.

Industrial use is one of the largest markets for powder paint. For example, the automotive industry is showing dynamic growth in this area.

Conclusion

The choice of powder coating depends on the application and is not merely a personal choice. Powder coating contains no solvents and the coating process produces no hazardous waste. The fact that excess powder which does not adhere to the metal during the process can also be recycled makes powder coating an environmentally friendly method.

To give aluminium profiles the required surface colour and properties, one of the anodising (anodic oxidation) or electrostatic powder-coating processes is applied. After anodising, the metallic surface of the aluminium is still visible, whereas after powder coating the surface takes on a more plastic-like appearance.

When we compare these 2 surface-treatment options:

Advantages of anodising:

• It is easy to maintain — it can be restored to its original appearance by wiping with water.
• It does not peel or flake.
• Because it is a transparent finish, the natural metallic surface of the aluminium is still visible.
• It is resistant to sunlight and does not fade. By contrast, organic coatings are affected by ultraviolet light.
• You see a consistent colour from any viewing angle.
• In structural silicone glazing applications where the glass is bonded to the aluminium with silicone, there is no peeling problem as there is with paint.
• There is no paint lifting or peeling, because the anodised coating is part of the surface.
• It is more resistant to physical contact and abrasive cleaning products. This makes it easier to use in places that can be reached and touched.

Disadvantages of anodising:

• It is weak against acidic urban pollutants.
• There are far fewer colour options than with powder coating.
• Matching the same colour is more difficult, especially with intermediate dark shades.
• Only matt and glossy finishes can be obtained.
• Because only aluminium can be anodised, matching it with other façade materials is difficult.
• Removing later scratches and similar marks is difficult.

Advantages of electrostatic powder coating:

• Matching colour is not an issue regardless of whether parts are produced in the same batch.
• Colour options are very wide.
• It is resistant to acidic and alkaline chemical cleaners.
• The process does not pollute the air.
• Powder paints emit zero or near-zero volatile organic compounds.

Disadvantages of electrostatic powder coating:

• If pre-treatments are not carried out correctly, what we call "filiform corrosion" can occur.
• Orange peel can occur.
• Chalking can occur.
• It is not suitable for bonding glass with silicone in structural silicone glazing.

Another advantage of aluminium is that, in aluminium frames made with thermally insulated profiles, the aluminium parts on the room-facing and outward-facing sides can be of different colours and can even be given different surface treatments. This means, for example, that a wood-effect finish can be provided on the room-facing side while the outward-facing side stays true to the colour of the building's external architecture (for example, a natural anodised colour). This is another advantage of aluminium frames.

Wood-effect aluminium is produced by laminating a wood-effect film onto the surface of aluminium profiles and heating them in an oven so that the pattern on the film is transferred onto the aluminium surface. The wood-effect coating process consists of 2 stages:

First, the aluminium profiles undergo electrostatic powder coating. In this process, a brown-toned primer is applied that determines the tone (light or dark) of the wood pattern (oak, pine, etc.).

In the second stage, the profiles are covered with wood-transfer paper and oven-cured under vacuum applied from both ends of the profile. During curing, the pattern on the paper is transferred onto the aluminium profile surface, and at the end of the process the films are removed.

Since different tones can be obtained with primers and different patterns with transfer paper, the number of possible different finishes is "primer tones" × "transfer-paper patterns".

It is recommended that wood-effect profiles hold the Qualideco certificate.

To enable aluminium windows to provide thermal insulation, plastic profiles are placed between the inner and outer shells of the aluminium profiles to prevent a thermal bridge from forming. So how are these thermal-insulation breaks fitted to aluminium profiles? And how is it ensured that the shear values meet the values specified by the standards?

Fitting a thermal-insulation break to aluminium profiles takes place in 4 stages:

Knurling the aluminium profiles

Knurling the channels in the aluminium profiles where the thermal-insulation breaks will be inserted is done to enhance shear strength. If this process is not done correctly, the thermal breaks will not be sufficiently clamped in the aluminium profile channels, and the profiles will fail to meet the required values in the rigidity test (shear stress test). Knurling machines work on the principle of running 2 special hardened discs over the aluminium profile. In a correct knurling operation, sharp teeth should be formed on the aluminium profile, and the spaces between these teeth should have an area 3 times greater than the teeth. This ensures the best possible grip between the 2 materials.

Inserting the thermal breaks into the break channels in the aluminium profiles (assembly, insertion)

Polyamide insulation-break manufacturers supply the profiles not only as length profiles but also, on request, as coils. To make it easier to insert the insulation profiles into the aluminium profiles — whether as length profiles or as coils — there are machines that have been developed for this purpose.

Crimping the thermal breaks into the aluminium profiles (curling, crimping, rolling)

Crimping (rolling / crimping) the thermal-insulation profiles that have been inserted into the aluminium profile channels is again carried out using machines designed for this purpose. For a good crimping operation, the settings best suited to the dimensions of the profiles are entered into the machine automatically or manually. The pressure settings must be carefully made to prevent twisting or breakage during crimping. Problems such as twisting, breakage or poor crimping may sometimes be due to the thermal-insulation breaks, but more often they are caused by the pressure created by discs not being correctly set for the profile.

Rigidity — shear strength test (rigidity test)

This is the stage at which we test whether the thermal breaks have bonded well to the aluminium profiles. The shear test allows the correct assembly of the composite profiles to be tested. All these stages are carried out with machines specifically designed for the sector.

There are many aluminium-profile manufacturing companies in Turkey. Most of them are located in and around Istanbul, Izmit and Tekirdağ, but aluminium-profile manufacturers (aluminium-profile factories) are found across the country, in Adana, Izmir, Konya, Zonguldak, Kayseri and elsewhere. Global large-scale system manufacturers choose to work together with Turkish aluminium-profile factories and have their profiles produced locally in Turkey. The aluminium extrusion (aluminium profile) companies producing in Turkey manufacture to a quality that meets these global firms' requirements. Many of these Turkish aluminium-profile manufacturers also have their own aluminium window, door and façade systems. In other words, they operate both as aluminium-profile manufacturers and as architectural aluminium window, door and façade system houses, architectural system designers and manufacturers. For this purpose, these aluminium companies either have their own in-house architectural product development offices or obtain external design support.

In the production of thermally insulated aluminium profiles, as important as the quality of the aluminium is the choice of the special plastics we call thermal-insulation breaks. Special plastics made of Polyamide 66 with 25% glass-fibre content have the same thermal expansion coefficient as aluminium and, with their high mechanical properties, are an excellent match with aluminium.

The list of aluminium-profile manufacturers below can be added to, on request and after notifying the website. Those who wish can also be removed from the list. This list has been prepared to help those looking for aluminium-profile manufacturers. In compiling this list, the criterion was that the companies hold at least one of the Qualicoat or Qualanod certificates. The scale and areas of expertise of these aluminium companies obviously vary.

Aluminium profile manufacturer companies