Steel Versus Aluminium

Overview

First and foremost, steel will rust regardless of any pre-treatment or top coat finish that is applied to it. Moisture is steel’s nemesis and considering the doors are usually on the outer wall of a building, they will receive a considerable amount of exposure to the natural elements, with certain areas of the doors likely to be continuously wet.

Maintenance

When exposed to moisture, in the form of rain, humidity, damp etc, steel will eventually succumb to rust over time. This not only effects its appearance but can also shorten the life expectancy of the door. Even if the steel is galvanised or powder coated to prevent corrosion any break in this coating, either during the manufacturing process or by damage/vandalism once installed will result in bare metal being exposed to moisture, resulting in corrosion.

Once corrosion has started it will spread under the protective coating to the rest of the steel. In fact, in most cases it will rust faster under the paint as moisture is trapped inside.

Aluminium on the other hand is naturally resistant to corrosion as it forms an aluminium oxide on the surface exposed to the atmosphere. This acts as a barrier to stop corrosion. This self-healing property makes it an ideal choice for coastal or humid regions. Aluminium doors are often anodised or powder coated, but this is merely a decorative finish and is not necessary for corrosion prevention.

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Strength

Although in principal the strength to weight ratio of high strength steel compared to high strength aluminium is very similar, steel doors are often made from the more readily available mild steel, whereas, high strength aluminium is a lot more common. In fact, high strength aluminium is the industry standard. There is usually very little difference in the strength of doors made from the two materials. Steel is perceived to be stronger, but a well designed aluminium door can be equally strong and often more resistant to attack than a steel door.

Weight

Steel doors are often heavier than aluminium doors. The added weight makes them more difficult to operate manually, and puts added stress and wear on the hinge, shortening the life expectancy of the door. Care and consideration needs to be taken when specifying steel doors, as the increased weight generally takes them beyond the recommended 20N for DDA.

Cost

Aluminium doors tend to be cheaper than steel on average, particularly when accompanied by a side screen. This is due to the versatility of the aluminium extrusion process which can produce quite complex shapes of differing thickness. The cost advantage is particularly noticeable on bespoke doors for refurbishment, where the versatility of aluminium sections can cope with virtually any shape of opening.

Appearance

Again the complex shapes of aluminium sections provide a more aesthetically pleasing appearance compared to the folded sheet steel sections used in steel doors. Aluminium doors look less “industrial” than steel doors and the residents do not feel “institutionalised” when they are fitted.

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Environmental

Both steel and aluminium are readily recyclable, but rusted steel is much more difficult to recycle and the yield of fresh steel from rusted steel is far less than aluminium. The recycling of aluminium requires very little energy compared to Steel, therefore aluminium is considered to be much more environmentally friendly than either steel or hardwood.

Stainless Steel

The use of stainless steel for door material alleviates some of the problems associated with rusting. Stainless steel will still rust due to the low chrome content, therefore when specifying stainless steel doors they need to be marine grade (316). The disadvantage of using stainless is again the weight and appearance but most of all the cost. Stainless steel can be as much as three times the cost of an aluminium door.