One of the most common questions we receive at Committas is whether a particular component should be fabricated from aluminium or steel. The answer depends on the application, environment, budget and performance requirements. Below we compare the two metals across the factors that matter most.
Weight
Aluminium weighs roughly one-third as much as steel for the same volume. In applications where weight reduction is critical — such as marine vessels, transport bodies, overhead signage and portable equipment — aluminium is almost always the better choice. Lighter assemblies are easier to handle, cheaper to ship and reduce load on supporting structures.
Steel, on the other hand, is often preferred when mass itself provides a benefit, such as in machine bases, counterweights and barriers designed to absorb impact energy.
Strength
Mild steel (Grade 250) has a yield strength of approximately 250 MPa, while common structural aluminium alloys (6061-T6) sit around 240 MPa. On paper, the numbers appear similar, but steel achieves this strength at a lower cost per kilogram and with a higher modulus of elasticity — meaning steel members deflect less under load for the same cross-section.
For highly loaded structural applications, steel generally wins on efficiency. For lightweight architectural elements, balustrades and cladding where loads are modest, aluminium delivers adequate strength with a significant weight saving.
Corrosion Resistance
Aluminium naturally forms a thin oxide layer that protects it from atmospheric corrosion. In coastal environments like the Gold Coast, this passive protection makes aluminium an attractive option for outdoor installations without the need for paint or galvanising.
Steel corrodes quickly when exposed to moisture and salt unless it is protected. Options include hot-dip galvanising, powder coating, paint systems and the use of weathering steels like Corten. Each adds cost and requires periodic maintenance, so the lifecycle economics need careful consideration.
Fabrication & Welding
Steel is generally easier and cheaper to weld, cut and form. Standard MIG and stick welding processes produce reliable joints with minimal distortion. Aluminium requires TIG welding with argon shielding and tighter heat control to prevent warping, porosity and burn-through — skills that not every workshop possesses.
At Committas, our welders are certified in both steel and aluminium processes, so we can advise objectively on which material suits your application without bias toward one or the other.
Cost
Raw aluminium typically costs two to three times more per kilogram than mild steel. However, when you factor in the weight saving, reduced finishing costs and lower maintenance over the life of the product, the total cost of ownership can be comparable — and sometimes lower — for aluminium in the right application.
For budget-constrained projects where appearance and corrosion are secondary concerns (warehouse racking, temporary structures, industrial frames), steel is usually the more economical path.
Recyclability
Both metals are highly recyclable. Steel is the most recycled material globally by volume, while aluminium can be recycled repeatedly with minimal quality degradation and at a fraction of the energy cost of primary production. From a sustainability perspective, neither metal has a clear disadvantage.
Making the Call
There is no universal winner. The decision should be driven by the specific demands of your project: load, environment, aesthetics, budget and lifespan. Our team regularly helps clients weigh these factors and select the most appropriate material before fabrication begins.