Aluminium and steel are both non-combustible metals widely used in Australian construction. Each has genuine strengths, and the choice between them often comes down to the specific application, environmental exposure, aesthetic requirements, and lifecycle expectations. This guide compares the two material types for facade and wall cladding applications, with a focus on the technical differences that matter most in practice.
How do aluminium and steel compare on corrosion performance?
This is the most significant technical difference between the two materials, and it is worth understanding properly.
Aluminium forms a thin, dense layer of aluminium oxide on its surface when exposed to air. This oxide layer is self-healing - if it is scratched or damaged, it reforms almost immediately. The result is a material with inherent corrosion resistance that does not depend on an applied coating for its durability. The base metal itself resists degradation. This is why aluminium performs well across a range of Australian environments, including coastal and industrial zones, without requiring specialised substrate treatments.
Steel, by contrast, requires protective coatings to prevent corrosion. The most common approach in Australian construction is hot-dip metallic coating - either zinc (galvanised) or aluminium-zinc alloy - applied to the steel substrate before it receives a paint finish. These coatings are governed by AS 1397, which defines coating classes by mass. For zinc coatings, common classes include Z275 (275 g/m2 total both surfaces) and Z450 (450 g/m2). For aluminium-zinc alloy coatings, AZ150 (150 g/m2) and AZ200 (200 g/m2) are typical for building applications.
These metallic coatings work through sacrificial protection - the zinc or aluminium-zinc layer corrodes preferentially, protecting the steel underneath. This is effective, but it is a finite resource. Over time, particularly in aggressive environments, the coating depletes. The rate of depletion depends on the corrosion zone, which AS/NZS 2728 classifies into six product types based on atmospheric severity, from very low (Category C1) through to very high marine (Category C5-M), with mild steel corrosion rates ranging from less than 1.3 microns per year in benign inland areas to 80-200 microns per year in severe marine environments.
Cut-edge corrosion is the practical Achilles heel for pre-painted steel cladding. Wherever the sheet is cut, drilled, or scratched during fabrication or installation, the steel substrate is exposed. The zinc coating at the cut edge provides some sacrificial protection to the adjacent exposed steel, but the unfavourable ratio of a small amount of zinc protecting a relatively large exposed steel area means this protection is limited. In coastal, tropical, or industrial environments, cut-edge corrosion can become a visible durability issue well before the rest of the panel shows any signs of deterioration.
Aluminium does not have this problem. A cut edge on an aluminium panel simply forms a new oxide layer and carries on.
What is the weight difference and why does it matter?
For pre-painted steel wall cladding in common gauges (0.42 mm BMT), the finished sheet weight is approximately 3.3-4.3 kg/m2 depending on the profile and coating class. According to AS 1397 Table C1, a 0.42 mm base steel sheet with an AZ150 coating has a calculated mass of 3.31 kg/m2 for the flat sheet alone.
For solid aluminium cladding panels like element13 (3 mm thickness, as used in flat panel facade systems), the weight is approximately 8.1 kg/m2. Extruded aluminium rainscreen profiles are typically lighter per square metre of facade coverage because of their hollow or semi-hollow cross-sections.
The real weight story is in the total installed system. Steel profiled sheet is often lighter per square metre of cladding, but aluminium’s lower density (2,680 kg/m3 versus 7,850 kg/m3 for steel) means that substructure components - brackets, rails, channels - are also significantly lighter. On multi-storey facades with substantial subframing, aluminium systems can meaningfully reduce overall dead load, with knock-on benefits for structural design and handling during installation.
How do the aesthetic options differ?
This is where the two materials diverge most clearly, and it is often the deciding factor on architectural projects.
Pre-painted steel is predominantly supplied as profiled sheet - corrugated, standing seam, mini orb, or flat pan profiles formed from coil. The colour range is set by the manufacturer’s pre-painted coil offering, and while this range is broad, it is a fixed palette. Steel cladding is well suited to applications where a consistent, cost-effective finish across large areas is the priority. The profiles available are proven, familiar, and widely understood by installers.
Aluminium opens up a wider range of architectural possibilities. Beyond powder-coated flat panels and profiled sheet, aluminium can be extruded into interlocking rainscreen profiles, formed into cassette panels, or incorporated into unitised curtain wall systems. Finishes include powder coat (with custom colour matching available), PVDF paint systems with superior UV resistance, anodised finishes that expose the natural metal character, and woodgrain or textured effects.
Anodised finishes deserve a specific mention. Anodising is an electrochemical process that creates a hard, integral oxide layer on aluminium - it becomes part of the metal rather than sitting on top of it. This gives a distinctive metallic appearance that cannot be replicated on steel. For projects where a natural metal aesthetic is specified, aluminium is the only practical option.
Both materials accept powder coating, and both can achieve consistent, durable painted finishes. The distinction is that aluminium offers the additional options of anodised finishes and architectural extrusion profiles that steel simply cannot match.
What about lifecycle and maintenance?
Aluminium facades have a proven service life of 50 years or more when properly installed and maintained. Coating warranties for quality powder coat or PVDF systems on aluminium typically extend to 20 years, covering colour retention, gloss, and film integrity. Maintenance involves washing with mild detergent and water every three months - more frequently in coastal or industrial environments - with no repainting required during the coating’s service life.
Pre-painted steel cladding has a typical service life of 25 to 40 years, depending heavily on the environment and the coating system. In benign inland environments, well-specified pre-painted steel performs reliably for decades. In moderate to severe environments, the paint system may need refurbishment after 15 to 20 years. Material warranties for pre-painted steel vary by environment classification - installations in severe marine or heavy industrial zones often fall outside standard warranty coverage, requiring project-specific assessment.
The lifecycle cost equation is not simply purchase price versus replacement cost. It includes the frequency and cost of maintenance, the likelihood of localised repair (easier with aluminium’s modular panel systems than with continuous steel sheeting), and the building’s design life. For a building designed to a 50-year life in a coastal environment, the total cost of ownership for aluminium and steel may be closer than the initial per-square-metre price suggests.
Comparison table
| Factor | Aluminium | Pre-painted steel |
|---|---|---|
| Combustibility | Non-combustible (tested to AS 1530.1) | Non-combustible (steel is inherently non-combustible) |
| Typical weight (facade cladding) | 2-8 kg/m2 depending on profile and thickness | 3.3-5.0 kg/m2 for 0.42-0.55 mm BMT sheet |
| Corrosion mechanism | Self-healing aluminium oxide layer | Sacrificial zinc or aluminium-zinc coating (depletes over time) |
| Cut-edge corrosion | Not applicable - oxide reforms at cut edges | Significant risk in coastal, industrial, and tropical environments |
| Coastal performance | Excellent - inherent salt resistance | Requires higher coating class; warranty exclusions may apply |
| Maintenance | Wash every 3 months, no repainting for 20+ years | Regular washing, possible repaint at 15-20 years depending on environment |
| Design life | 50+ years | 25-40 years (environment dependent) |
| Finish options | Powder coat, PVDF, anodised, woodgrain, custom colours, textured | Pre-painted from coil (manufacturer’s colour range) |
| Profile options | Interlocking rainscreen, flat panel, extrusions, curtain wall | Corrugated, standing seam, flat pan, mini orb |
| Thermal expansion | 23 um/m/K | ~12 um/m/K |
| Recyclability | 100% recyclable, retains full value | Highly recyclable (steel is one of the most recycled materials globally) |
| Relative cost per m2 | Higher | Lower, particularly for profiled sheet |
| Typical applications | Architectural facades, rainscreen, curtain wall, coastal projects | Roofing, industrial cladding, residential wall cladding, cost-sensitive projects |
When is each material the right choice?
Pre-painted steel is well suited to:
- Cost-sensitive projects where profiled sheet meets the design intent
- Roofing applications (steel’s spanning capability and established fixing systems are well proven)
- Industrial and commercial wall cladding where a clean, consistent finish is the priority
- Inland environments with low to moderate corrosion exposure
- Residential wall cladding where the profiled sheet aesthetic is appropriate
- Projects with shorter design lives or where future refurbishment is planned
Aluminium is well suited to:
- Architectural facades where design intent requires interlocking panels, flat panels, or curtain wall
- Coastal, marine, and industrial environments where long-term corrosion resistance is critical
- Projects requiring anodised or custom finishes
- Multi-storey facades where system weight matters
- Buildings with long design lives (50+ years) where lifecycle cost is prioritised over initial cost
- Applications where panel-level replaceability is important for ongoing maintenance
Both materials share common ground. They are non-combustible, recyclable, and proven in Australian conditions. Both can deliver a durable, attractive facade when specified correctly for the environment. The differences are in the detail - and the detail matters.
What about galvanic corrosion when using both materials together?
It is common in construction for aluminium cladding to be fixed to a steel subframe, or for aluminium and steel components to be used in close proximity. When two dissimilar metals are in contact in the presence of moisture, galvanic corrosion can occur. In an aluminium-steel pairing, the aluminium is the less noble metal and will corrode preferentially.
This is a well-understood risk with straightforward solutions. Isolating the two metals with neoprene washers, EPDM gaskets, or plastic separation strips prevents direct metal-to-metal contact. Using stainless steel fixings with isolating sleeves is standard practice for bolted connections. The key principle is to break the electrical path between the two metals and, where possible, prevent moisture from bridging the junction.
This is not a reason to avoid combining aluminium cladding with steel structure - it is done routinely and successfully across thousands of Australian projects. It simply requires the detail to be right, which any experienced facade installer or engineer will understand.
Choosing the right material for the project
The right choice depends on the project’s priorities - budget, environment, design life, aesthetic intent, and maintenance expectations. There is no universal answer.
Valmond & Gibson supplies aluminium facade systems - interlocking rainscreen, solid panels, and curtain wall - so our experience sits firmly on that side of the comparison. But pre-painted steel cladding is an excellent, proven material that serves the Australian construction industry well, particularly in roofing and cost-sensitive wall cladding.
If your project involves an architectural facade, a challenging corrosion environment, or a requirement for anodised or custom finishes, aluminium is worth serious consideration. If the application is straightforward wall cladding in a benign environment and cost is the primary driver, pre-painted steel may be the more practical choice. The best outcomes come from understanding both options and specifying the right one for the job.
Related Reading
- Aluminium vs Fibre Cement Cladding: What Specifiers Need to Know
- Choosing the Right Aluminium Facade System for Your Project
- How Long Does Aluminium Cladding Last?
- Aluminium Facades in Coastal Environments
Last updated: 3 April 2026