Naturally Aluminium

I'm often asked the question, 'Which is the best method for joining aluminium?'

The answer is 'It depends'. It's not a question of which one is best but rather understanding the pros and cons of each process and relating this to the intended application.

On this occasion we will consider welding. Welding is one of three principal methods by which aluminium parts can be successfully joined together. Bonding (structural adhesives) and using various mechanical means (cleating, folding, nuts/bots, screws, rivets, etc.) are the alternatives.

Carrington House, London:Aluminium Squeeze Frame Panels with welded & cleaned off corners

Welding is often rightly thought of as one of the strongest and most permanent joining methods. This heat intensive process involves fusing separate aluminium items together and then using a filler to form a joint. There are different techniques for welding aluminium (MIG & TIG). The material thickness of the parts to be welded will often determine the most suitable mode.

When considering welding, however, as a preferred joining method 'casuality' (cause and effect) should be borne in mind. The event of welding can change the localised form and appearance of the aluminium. For many applications these considerations are of little or no consequence, but where aesthetic considerations apply, care should be exercised. It is always good to know in advance what visual and other effects might manifest from a process.

One of aluminium's primary advantages is it's resistance to atmospheric corrosion. This corrosion resistance is due to the oxide coating that naturally forms on aluminium's surface.

Pharmacia, Milton Keynes: Mill aluminium (c/w natural oxide coating)

The aluminium oxide coating has a much higher melting point (2037 C) than the aluminium base metal (648 C)and therefore needs to be removed before welding takes place. Oxide removal is usually achieved by means of using a wire brush or solvents and etching solutions immediately prior to the welding process.

Satisfactory welds require a high heat input and this can cause distortion to the metal's form and bring impurities to the surface. The filler metal used also results in producing a weld bead that stands proud of the metal and can be considered unsightly and is therefore sometimes removed.

Simply Red fabricated gantry: Fabricated aluminium with weldbeads highlighted in red

As we know oil and water don't mix and in most cases anodising and welding don't either. Anodising thickens the naturally occuring aluminium oxide film, thereby preventing satisfactory weld penetration. Alternatively anodising of a pre-welded aluminium part can reveal unsightly discolouration (caused by impurities rising to the surface) around the area of the weld.

Leeds Bradford Airport: Anodised Column Casings

To summarise:

Weld beads can be 'cleaned off' if a flush surface is required (subject to adequate structural strength).

Metal grinders are normally used to remove weld beads resulting in unsightly grinding marks. These markings can be covered with a surface coating or blended in with a linished effect.

Avoid the welding of pre-anodised material (due to insufficient weld penetration).

Steer clear of anodising welded parts if aesthetics around the welded areas are important.

The high heat input with welding can result in material distortion. Lighter gauge materials are particularly susceptible.

You can always contact one of our helpful Project Managers who will be pleased to assist with your enquiries.

It was non other than Ludwig Mies van der Rohe, the creator of the Barcelona Pavillion, (which is often described as one of the most beautiful 20th century buildings), who coined the phrase 'less is more'. Van der Rohe could have been talking about perforated aluminium sheet!

What other material simultaneously provides so many design opportunities to combine its inherent strength to weight ratio and corrosion resistant qualities with a widely appreciated aesthetic appeal? By virtue of these outstanding attributes, perforated aluminium sheet is often incorporated into many architectural components as the primary element. These products would include balustrade infils, bar/counter fascias, ceiling panels, column casings, radiator/vent covers, wall cladding and so on.

Jesus College: Cambridge - Student Bar: Perforated Aluminium Sheet with Squeeze Frames

It is often desirable to custom make perforated aluminium panels rather than fabricate from stock size sheets. This way the specifier retains much greater design flexibility by being able to incorporate plain borders and other unpunched areas, as well as, cut outs for lighting, vent ducts, etc. With the majority of round hole patterns being arranged on a 60 degree triangular pitch the plain borders are normally lost once pre-punched sheets are cut to size. Unless covered with a safety edge or hidden by some other component the resulting raw edge is a health and safety no no. 

Digitas & Modem Media: London - Perfoated aluminium ceiling panels with plain borders

The paradox with perforating metal is that it is both relatively straightforward  and at the same time surprisingly complex. Every time a hole is punched a degree of surface tension is created. The downward movement of the punch produces compression at the bottom of the sheet, in a similar way when trying to push a finger through plastic film. A variety of production techniques are therefore employed to negate the arising tension. These methods include balancing the surface stresses by punching alternate parts of the aluminium sheet, rather than whole areas at a time, and roller levelling to counteract surface tension. The effects of roller levelling can be compared with a sports massage easing muscular tightness.

Rimmel Cosmetics: Ad set - Back lit perforated aluminium wall cladding

As you may appreciate, to ensure a satisfactory level of surface flatness, certain production ratios are to be observed during the perforating procedure. Having selected the preferred hole size and pattern configuration, material thickness, width of plain borders, etc., you can contact us to check the proposed panel designs meet the required production criteria.

Exeter University: Perforated & Anodised Column Casings

The many advantageous characteristics of perforated aluminium sheet are available for enhancing your architectural designs in many different and ingenious ways.

Most of us will be familiar with the 19th century architect and engineer Issambard Kingdom Brunel and at least some of his awe inspiring designs for bridges, railways, tunnels and ships. However, there is another less well known, but no less accomplished engineer and architect from the same period and his name is Henry Robinson Palmer. Apart from founding the Institute of Civil Engineers, Henry Palmer also patented the first Monorail design in 1821 and is credited with inventing corrugated iron and the galvanising process. 

The principle advantage of corrugating materials is that although it doesn't make them any stronger as such, it does increase their rigidity by virtue of spreading any applied load along the length of the corrugations.

Combining Henry Palmer's brilliant corrugating idea and applying this to a modern day corrosion resistant and lightweight material such as aluminium sheet produces an outstanding multi functional product.

Anolight Aluminium Sheet:Gatechrasher Nightclub, Birmingham 

Anolight Aluminium Sheet: Dorman Museum, Middlesborough

As with all claims for improved product performance, some clear cut evidence is required to demonstrate just how much of a difference the corrugating process makes to the rigidity of an aluminium sheet.

Ceram Research therefore recently carried out deflection testing on our range of wavy Anolight aluminium sheets and compared the results with a control sample of flat aluminium sheet. The test results exceeded my expectations and will be shortly uploaded onto our website. In the meantime here are the essentials.

A synopsis of the test conditions reads as follows. Load was applied by means of dead weights placed centrally on the aluminium sheets. Deflections were measured at each load increment until either the sample collapsed or the maximum load was achieved.

Test Rig with Anolight Aluminium Sheet

The test results showed that, compared with the control sample of flat aluminium sheet, the wavy Anolight material had an impressively increased resistance to deflection of between 8 & 15 times (depending on the sheet patterns tested).

Corrugating sheet material is a great example of innovation. Sometimes the simplest of ideas are the best. We have a lot to thank Henry Robinson Palmer for!

Being both lightweight and ductile, aluminium readily lends itself to fabrication.

However the un-initiated should tread carefully as there is no substitute for experience in specifying fabricated aluminium. It might, therefore, prove helpful if I share some key pointers with you, and these are;

ProductionTolerances:                                                                                                                                                                                                                         How long is a piece of string? There is no such thing in fabrication as an exact dimension. Every measurement is subject to a production tolerance. If sizing is critical, make sure you agree specifics with us before fabrication commences. If requested and to ensure a satisfactory 'fit', we can normally provide measurements that are 'no greater than' or 'no less than'.

Aesthetics:                                                                                                                                                                                                                                  To quote from Shakespeare 'Beauty is bought by judgement of the eye'. Workshop processes will literally leave their mark on all metal surfaces. If aesthetics are important, and they often are, consider the intended location of the fabricated items. Lighting conditions, viewing distance and angle, etc., are among the elements that need to be taken into account.

Working from the premise that 'prevention is better than cure', sheet materials can be covered with a peelable protective film prior to production. This best practice precaution certainly assists in reducing, but not necessarily completely eliminating, surface marking.  Sheets are normally supplied with one good side (unless otherwise specified). It is also sometimes possible to 'hide' surfaces liable to workshop abrasions, as long as the visible faces are identified to us prior to fabrication.

Image: Aluminium sheet with protective peelable film

It should be understood that with tonnage pressure and the types of processes involved in fabricating aluminium, surfaces will often incur some degree of marking. For patterned and perforated materials, the surface design and texture will certainly assist in reducing the visibility of these abrasions, sometimes rendering them almost invisible to the naked eye. Plain materials, however, can require post production surface finishing.

Image: Can you see the surface abrasions in this perforated sheet? Probably not!

Sampling:                                                                                                                                                                                                                                  An excellent investment, and a very good way of avoiding the unexpected turning up on site, is arranging for a 'one off' sample to be produced. Although initially chargeable, sampling costs can be considered a cost effective method of avoiding possible delays at a later stage. The good news is, that on larger scale projects sampling costs are normally refunded against the bulk order value, thereby effectively making the sample free of charge. A win win situation, if ever there was one!

Image:Pre-production sample of a modified GA Ver T Fix Panel Hanging System

Communication:                                                                                                                                                                                                                        It's good to talk! Many potential pitfalls can be avoided simply by discussing your proposals with our team of knowledgeable project managers. Whatever your requirement we will endeavour to help you find a suitable solution.

Image: We are always pleased to assist with your enquiries

It is widely accepted that surface patterns and textures assist in disguising minor surface abrasions such as indentations, scratches and other undesirable markings.

With plain surfaces it seems that no matter how large the area and how small the damage, the eye will register the offending mark and return to the exact same spot time and time again. How annoying is that first scratch on the newly acquired glass table!

Fortunately there are a wide range of patterned and textured aluminium surfaces that help to conceal undesirable surface markings.

However the question of surface marking is highly subjective, with 'beauty being in the eye of the beholder' etc. I therefore decided to commission some independent testing to establish a scientific basis for these claims. Ceram Research carried out the laboratory analysis on our behalf.

Full test results for this research will be uploaded onto our website in due course. In the meantime I would like to share a sample of these findings with you.

GA Vertex sheet (a small pyramidal pattern) was tested in both mill and anodised finishes and was compared with a reference sample of plain mill finish sheet.

Fitness First Lesure Centre, Haringay, London (Vertex (VXM21) Mill Finish Sheet)

                     Vertex (VXM21) Mill Finish                                         Vertex (VXS21) Anodised Finish

Briefly, the test method involved using P40 grade (rough grit) emery paper and this was attached to lead weights and a mechanical device pulled the emery paper along the aluminium surfaces.

Only 1 pass of the emery paper was required to produce a noticeable difference to the surface of the plain mill finish sheet. Significantly a minimum of 40 passes were required in both mill and anodised finishes of the Vertex pattern to produce a similar effect.

In culinary terms 'the proof is in the eating' and in metallic terms 'the proof is in the testing'. Ceram's testing has established beyond resonable doubt just how effective aluminium patterns and textures can be in disguising surface damage.

For those in the know, great; but for those that don't, the question surely arises - What is the connection between Charles Goodman and Aluminium Houses?

Image: Alcoa 'Care Free House'

Charles Goodman was a Washington DC based architect who specialised in designing homes in the modernist style. Inspired by, amongest others, the Bauhaus work of Mies van de Rohe, Goodman was appointed in 1957 by Alcoa (The Aluminum Company of America) to design the 'Care Free House'. This collaboration was set up to demonstrate aluminiums' suitability and versatility as both a decorative and structural material within residential environments. It was also intended to display how successfully aluminium integrates with traditional materials such as brick, glass, stone and wood.

Image: Living Room

For whatever reason, only twenty three of these high quality 'California Style' post and beam construct houses were ever built. Fortunately a proportion of these unique properties have either been preserved in their original condition or, renovated with meticulous attention to detail.

Image: Open Plan Kitchen / Diner

You can also view a real estate agent's video promoting one of these 'For Sale' homes.

Reassuringly there is a growing awareness in the United States that such distinctive mid 20th century properties should be protected from the trend towards demolition and MacMansionization, as the Americans' call it!

Goodman was also responsible for designing several housing developments that have been subsequently 'listed', including the superbly landscaped Hollin-Hills in Alexandria, Virginia.

Images: By courtesy of Retro Renovation 

Ever heard the expression 'We tend to receive what we expect'? Well this sentiment doesn't always apply when mill finish aluminium is being considered.

In Google terminology it is a generally accepted 'knol' (unit of knowledge) that aluminium is a long lasting lightweight metal with minimal on-going maintenance requirements.

There are many different surface finishes that can be applied to enhance the appearance of aluminium; anodising, powder coating and satin brushing are just three examples. However mill finish aluminium is not one of them! Mill finish is not an applied finish but simply untreated aluminium.

For whatever reasons some names just stick; Escalator for moving stairway; JCB for excavator etc., and mill finish for unfinished aluminium. This term often raises expectations and mistakenly leads the unwary into expecting an immaculate surface finish. So let's attempt to close the knol gap when it comes to the appearance of mill finish aluminium.

For those with the time and inclination to study this issue in detail the Aluminum Association of America publish booklets detailing numerous examples of aluminium's surface finish attributes. However for a brief overview please read on.

Once the extrusion or rolling mill has manufactured the aluminium into the desired shape and size the material is said to be in the mill finish condition.

So what are the visual characteristics of untreated aluminium? Extruding aluminium, as opposed to rolling sheet, produces differing surface finish effects so let's consider them separately.

Extrusions are produced by either pushing or pulling aluminium (in a heated/softened state) through a hardened steel die. This process produces both simple geometric shapes (angles, channels, etc.,) and the more complex 'purpose made' designs. All of these forms normally display longitudinal lines of varying width, texture and tone. Various surface abrasions may also be apparent. The standard architectual grade (6063) is normally quite shiny and this tends to highlight such features. Despite these factors there are many instances where mill finish is successfully incorporated into a large number of projects (both seen and unseen). It is usually only when surfaces are going to be viewed at close quarters, either in aesthetically demanding situations or in particulary 'aggressive' atmospheres , that this industrial finish benefits from a finishing operation of some kind.

 Image: Aluminium extrusions in mill finish

Aluminium sheet is produced in a similar way to flattening pasty with a rolling pin. The constant backwards and forwards rolling process reduces the material to the required gauge thickness and temper (hardness) and in so doing the sheet becomes 'polished' to some degree. The alloy mix of the aluminium will also effect the materials' brightness and reflectivity. Sheets will sometimes display rolling bands or stripes and may also commonly possess a grainy type finish.

Image: Aluminium mill finish sheet 

A finer surface appearance can normally be achieved by selecting anodising or architectural quality aluminium. Our industry recognises that items required for these applications require a higher surface finish standard as opposed to general commercial applications.

In summary, aluminium materials that are going to be closely scrutinised would usually benefit from an applied surface finish. However there are many applications where mill finish is perfectly acceptable.

Interestingly, mill finish aluminium sheets with variable surfaces, including patterned, perforated and textured designs often prove an exception to the above rule by lending themselves to a wider use of mill finish due to their surface topography and consequent distorting optical effects, where marks and blemishes are often disguised.

Before reaching a final decision on surface finish our Free Samples Service is available to provide a range of alternative finishes.  

There have been many technological advances in the mining and production of aluminium over the past 50 years. Significantly reduced power input, lowering of PFC emissions, increased re-cycling, and the development of new industry specific aluminium alloys to name a few.

The basics of making aluminium however remain the same. Bauxite, the main ore of aluminium, is open cast mined, converted into aluminium oxide (alumina) and passes through an electrolytic reduction process that converts into metallic form.

The complete cycle from mining bauxite in Jamaica to manufactured item is brilliantly portrayed in a glorious '50's Technicolor 'time warp' film commissioned by Reynolds Metals of America (at the time the world's 3rd largest aluminium company).

Not only does this iconic industrial film cover everything you are likely to want to know about aluminium but it also manages to capture the essence of the post-war All American Dream. (the soundtrack is quite something!)

Image: 1950's classic colonial style home with painted aluminium siding (courtesy of http://retrorenovation.com)

However 'green fingered' or not, most of us would probably acknowledge a basic understanding of the way living plants progress through a life cycle, changing their forms as part of the process. Remarkably, for an inanimate material, aluminium also has the sustainable and environmentally friendly capability of changes in form, passing through potentially numerous life cycles by being recycled from one product into another. No wonder aluminium is called the greenest of metals!

For another 'natural' analogy you can also consider comparing aluminium with secondary clay. Both materials, originating from the earth's crust, are in abundant supply; both are solids and yet lend themselves to changes in form through cold working and/or various forms of heat treatment. Interestingly there are clay building products that can be recycled by composting, while aluminium is recycled through re-melting and manufacturing into new shapes and products.

The worldwide annual recycling of aluminium is very much expanding with a three fold increase from 5 million tonnes in the early 1980's to something in the region of 15 million or more tonnes in the mid naughties. It is currently estimated the construction industry is recovering over 90% of the aluminium used in redundant buildings (96% of the aluminium from the old Wembley Stadium was recycled).

The relatively high value of scrap aluminium helps to ensure a healthy interest in environmentally friendly recycling! In fact, aluminium's scrap value is such that it is the only packaging material whose value exceeds the costs of its collection and recycling.

Uniquely aluminium can be continuously recycled while preserving its inherent physical properties. Most importantly, there is a 95% saving in the energy required to re-cycle aluminium as compared with original smelter production. With energy being converted rather than created today's manufactured aluminium results in what is effectively a stored energy resource for future generations. The time will surely come when the world's aluminium needs will be satisfied solely from recycling rather than from primary production.

Are there any other 'green' aluminium issues you would want covered in future blogs? Please add a comment.

Even the briefest of Google searches for 'advantages of aluminium' will present a plethora of statements extolling the virtues of aluminium. Among its many attributes are said to be its lightness, strength, flexibility, durability and corrosion resistance. At first sighting the uninitiated may be forgiven for asking, 'how can this be?' How is it possible that one metal can possess all of these qualities?

The good news is all of these 'wish list' properties can be accurately attributed to aluminium, or rather aluminium alloy. The key word here is 'alloy'. Alloys are the other metals that are added to aluminium, in relatively small amounts, to produce the required performance characteristics (along with post-production processess that include cold working, heat treatment, etc.). It is a combination of these factors that mark aluminium alloys out as such truly versatile materials.

To fully appreciate the performance enhancing benefits of alloying aluminium let's consider Aluminium in its pure state. Unalloyed aluminium has a yield stress (the stress at which a material begins to deform plastically) of around 7-10MPa. The range of aluminium alloys, normally used within the architectural industry, usually produce somewhere in the region of 100-200MPa. without necessarily being a graduate engineer you get the drift! The addition of alloy to aluminium is perfomance enhancing and could be equated with an athlete consuming chemical supplements to build muscle mass, but with only desirable side effects. 

It should be understood that the mechanical properties of a particular aluminium alloy will vary considerably dependent on the form type, be it extrusion, sheet, casting etc., in addition to the amount of work hardening, heat and solution treatment, applied post production.

For instance let's take a look at specification 6063 (a commonly used extruded architectural alloy) to see how beneficial the addition of small quantities of alloy are. This alloy grade (when heated) is sufficiently plastic to allow for the production of small intricate profile shapes and after cooling, for subsequent cold working techniques to be carried out e.g. rolling into curves and rings. At the same time this aluminium alloy is strong and rigid enough to be selected as suitable for panel hanging systems. Independent tests have demonstrated the interlocking profiles (illustrated below) to be capable of suspending the equivalent weight of a small car! As an added bonus, 6063 alloy is also a suitable grade for the anodising process.

Image: GA WP1 Panel Fixing Profile

Details on the properties of aluminium and its alloys can be obtained from the Aluminium Federation.

In relation to our materials and products is there any specific performance data you would like us to publish for future reference?