Aluminum has been called a ‘magical metal.’ Mainly found as Bauxite ore, it’s the third most common element in the earth’s crust and the most abundant metal on the planet. But what makes it perfect for windows, doors, and curtain walling?
Well, the chemical, physical and mechanical properties of modern-day aluminum alloys account for the steep rise in its global use at over 5% every year. Here are just eight advantages of aluminum window frames in the glazing world continues to grow, now dominating the commercial market and giving PVC-U a run for its money in the residential sector.
Aluminum Window Frames are Lightweight
Aluminum is a very light metal with a specific weight of just 2.7 g/cm3, about a third that of steel or copper. Unfortunately, it’s one of the most delicate commercially available metals. This makes it ideal for window and door frames, but a lightweight frame is crucial for curtain walling. Curtain walls are not structural and can only carry their weight, so the lighter, the better.
Resistant to corrosion
If you’re looking for a low-maintenance window, aluminum is your answer. That’s because when aluminum comes into contact with air, a protective layer of aluminum oxide immediately forms on the surface. This layer is exceptionally resistant to corrosion from anything the weather can throw, including acid rain, and won’t be damaged by cleaning products. And unlike timber or PVC-U frames, aluminum window frames won’t swell, crack, split or warp over the years, whatever the weather. Protection from corrosion can be increased even further by anodizing or painting (usually by powder coating) the surface.
Aluminum Window Frames Won’t Easily Break
Aluminum is both malleable and ductile – in case you’ve forgotten your GCSE chemistry, it can be bent or pressed into shape or drawn out into a thin wire without losing its toughness and breaking or cracking. In other words, it’s pliable, not brittle. Aluminum is the second most malleable metal and the sixth most ductile. This is fantastic news for anyone wanting a curved curtain wall or window, as the aluminum frame profiles can easily be bent or pressed into the required shape without any danger of them breaking.
Aluminum Is 100% Recyclable.
Aluminum is unique when it comes to recycling metals. It is 100% recyclable, and the quality of recycled aluminum is identical to that of virgin aluminum. Which means it can be recycled again and again. Nearly 75 percent of all aluminum ever produced is still in use today. This is good news for aluminum supply, especially considering that since the first industrial quantities of aluminum were made around 100 years ago, worldwide demand for aluminum has grown to approximately 29 million tons annually. But it’s even better news for the environment because while it takes 14,000 kWh to produce 1 tonne of new aluminum, it only takes 5-10% of this to remelt and recycle the same amount, which means a smaller carbon footprint and lower costs.
Aluminum Is Very Strong
Aluminum alloys are used to make window door and curtain wall frames. That’s because pure aluminum, on its own, doesn’t have high tensile strength. However, its strength increases vastly once it is alloyed with other elements like manganese, silicon, copper, and magnesium. The tensile strength of pure aluminum is around 90 MPa but can be increased to over 690 MPa as an alloy.
As we’ve already seen, aluminum is one of the lightest engineering metals and has a far better strength-to-weight ratio than steel when used as an alloy. Even more impressive, unlike steel, the strength of aluminum increases the colder it gets, whereas steel becomes brittle at low temperatures (below 0oC). This means that aluminum window frames, doors, and curtain walling can more than cope with the most extreme winter temperatures in the UK. For example, the lowest temperature recorded in the UK was -27.2°C in Scotland.
Readily Forms Alloys
As we’ve already seen, aluminum is usually alloyed with other elements to improve its physical properties. For example, the strength of pure commercial aluminum can be increased by 20% by adding manganese. Aluminum also readily forms alloys with silicon, copper, zinc, iron, and magnesium. This means producing a range of alloys with properties tailored to particular applications is possible. For example, aluminum glazing firms use aluminum alloys with silicon and magnesium, which are excellent choices for extruded aluminum profiles. They are versatile, heat treatable, highly formable, weldable, and have high strength and superior corrosion resistance.
Aluminum Is Easy to Make Into Frames
Aluminum window frames are made using an extrusion process, i.e., by forcing the pre-heated aluminum alloy through a die to create an aluminum profile. These profiles are then joined together to form the frame. The design of these profiles gives the window frame its unique characteristics. They can be complex designs, but these intricate shapes can be achieved using a single extruded section to make the profiles both solid and durable. Aluminum also has good machinability, making it easy to fabricate the aluminum profiles into the finished window frame accurately.
Aluminum Can Be Decorative
Aluminum can be easily anodized or powder coated to give it a decorative smooth or textured finish. This means that aluminum window frames, doors, and curtain walling perform well and look fantastic. Anodising is carried out by immersing the aluminum in an acid electrolyte bath and passing an electric current through it. This makes the metal surface a decorative, durable, corrosion-resistant aluminum oxide finish. In addition, the aluminum oxide is fully integrated with the underlying aluminum, so it cannot chip or peel, making it amazingly durable.
Aluminum oxide has a porous structure, so it needs to be sealed to make it resistant to corrosion. The sealant can be transparent or contain special dyes, so anodized aluminum is available in many colors. The alternative is to powder coat the aluminum with paint. The aluminum is pre-treated either by anodizing or via a chemical reaction to form a corrosion-resistant barrier and can then be powder coated in any RAL color. Senior Architectural System has a state-of-the-art powder coating facility at Denaby.
The pre-treated aluminum bars are earthed, and the paint powder is given an electrostatic charge as it leaves the guns. This helps the powder molecules to stick to the bars via electrostatic charge, just like dust particles stick to your TV due to the electrostatic charge on the screen! The bars are then cured in an oven where the powder melts and forms a uniform, flexible, smooth finish resistant to weathering for 25 years.