Steel vs Aluminium Trailers: The Preferred Choice

Steel is the fabrication material of choice for the vast majority of engineering projects and it has definitely got our vote for trailer builds.

Despite our preference, we want to provide an overview of steel vs aluminium when considering building a trailer, to help you decide what is right for you and your needs.

Please note that we are comparing steel and aluminium in a general sense. Both steel and aluminium come in a large variety of alloys, therefore some of the discussion below will not hold true for all varieties.  

Aluminium trailers

Aluminium trailers are typically hailed for being lighter and rust resistant. 

The ‘lightness’ of aluminium is due to the lower density of aluminium vs steel (approx. 2700kg/m3 vs 7800kg/m3). Don’t get too excited about an aluminium trailer weighing half that of a steel one. Despite what these numbers suggest, an aluminium trailer usually requires more material in order to match steel, resulting in a weight saving of around 10-15%.

Unlike steel which rusts, aluminium corrodes. Corrosion like rust, is an oxidising process where aluminium reacts with oxygen in air and water. This forms a thin coat of aluminium oxide which thickens over time.

Aluminium corrosion presents itself as a thin, hard film which doesn’t flake unlike rust. This can be removed with an acid wash to make your trailer look new again. Be careful as the acid removes a thin layer of your trailer every wash. There are other options available that are not as harsh, like Aluma-Brite.

Aluminium also requires specialised welding machines, your standard run of the mill MIG just won’t cut it. These machines can be found for as low as $4000 but can get up into the 10’s of thousands – not a machine your everyday shed has! On top of this, there is a higher degree of skill required to successfully weld aluminium.

You should also be aware that a welded aluminium joint handles stress vastly different to a steel joint, hence why you often see aluminium trailers being bolted together rather than welded. This has to do with the strength qualities of a bolted joint.  

Pros and cons of building an aluminium trailer

PROS	CONS
Corrosion/rust resistant (generally speaking)	Your standard welding machine won’t work
Lightweight	More expensive (up to 60-80%)
Does not require surface treatment/painting	Less rigid & stress cracking

Steel trailers

Steel trailers on the other hand, are trusted for their rigidity and lower cost.

The flexibility of steel is far lower meaning it is more rigid and deflects less under load. Material flexibility can be good, but a trailer that flexes more under every bump or with every load it carries will experience more stress over time. Stress on your trailer parts ultimately leads to cracks as welds or holes become fatigued. 

If cost is your main consideration, you’ll be happy to choose steel when you know it is less than half the price of aluminium! 

If you are new to fabrication, then it is highly recommended that you build your trailer from steel. Not only is the material much cheaper, the tools are cheaper and the learning curve required to weld steel is much faster and easier than trying to get your head around aluminium welding. 

Another factor to consider is that steel is more readily available in a greater variety of sizes. Most people can collect the steel they require to build one of our trailers from their local steel market, whereas you may have to wait weeks for aluminium stock to be ordered in. 

Pros and cons of building a steel trailer

PROS	CONS
Easy to weld	Requires surface treatment
Cheaper	Higher maintenance (due to rust risk)
More rigid	Heavier than an aluminium equivalent

Why we recommend steel built trailers

With the DIY builder in mind, we recommend steel-built trailers for the following reasons:

1. Lower cost: Aluminium is far more expensive than steel.
2. Less flex: Aluminium is on par with the strength of steel, but lacks the rigidity of steel.
3. Easy to work with: For the DIY trailer builder, welding with aluminium requires a lot more skill than steel, not to mention specialised equipment. Steel can be welded using a stick or MIG welder (see our Tools Guide).

> Aluminium has its place. It is a great material for boat trailers and ute trays along with canopies.

Can I follow Fabplans drawings to make an aluminium version of my trailer?

Unfortunately, you cannot follow our drawings to make an aluminium version of your trailer. Steel and aluminium have different mechanical properties (they are different materials) and fail in different ways. While our plans have been tested for steel, they have NOT been tested for aluminium. 

Choose Steel. Choose Fabplans.

All our trailer plans and ute tray plans utilise the advantages of steel to ensure your car trailer, hydraulic tipper trailer or dual cab tray outlast any mass-produced equivalent. Cut costs now and get building with the plan of your choice.