Why Material Selection Matters
Selecting the right metal is one of the most important decisions in any fabrication project. The material you choose affects everything: the structural performance of the finished product, its resistance to corrosion and wear, its weight, its appearance, and ultimately its cost. Choosing incorrectly can lead to premature failure, unnecessary expense or a product that simply does not perform as intended.
At Alliance Metal Solutions in Somersby, NSW, we fabricate components from mild steel, stainless steel, aluminium and various specialty alloys. Our experience across thousands of projects gives us a practical understanding of how each material behaves in real-world applications. This guide compares the three most commonly fabricated metals to help you make an informed choice for your next project.
Mild Steel
Properties and Characteristics
Mild steel (also called low-carbon steel) is the most widely used metal in fabrication. It contains between 0.05 and 0.25 per cent carbon, giving it good strength and ductility while remaining easy to cut, bend, weld and machine. Common grades used in Australian fabrication include AS/NZS 3678-250 and 350 for plate, and G250 and G450 for cold-rolled and galvanised sheet.
Mild steel has a tensile strength typically in the range of 400 to 550 MPa (depending on grade and form), making it strong enough for the vast majority of structural and general engineering applications. It is highly weldable using all common welding processes, and it bends and forms predictably with minimal risk of cracking.
Advantages
- Cost: mild steel is the least expensive of the three major fabrication metals, typically 30 to 50 per cent cheaper than stainless steel and comparable to or less than aluminium on a per-kilogram basis
- Availability: available in the widest range of forms, grades and sizes, with short lead times from Australian steel distributors
- Weldability: excellent weldability with all common processes and no special shielding gas requirements
- Machinability: machines well with standard tooling and feeds
- Strength: high strength-to-cost ratio, making it the default choice for structural applications
Limitations
The primary limitation of mild steel is its susceptibility to corrosion. Without a protective coating—such as powder coating, galvanising or painting—mild steel will rust when exposed to moisture and oxygen. This is manageable through appropriate surface treatment, but it does add a step and cost to the fabrication process. Mild steel is also the heaviest of the three metals discussed here, with a density of approximately 7,850 kg/m³.
Best Applications
Structural steelwork, general engineering, machine frames, brackets, enclosures, agricultural equipment, trailers, guards and any application where strength and cost are the primary drivers and weight is not critical.
Stainless Steel
Properties and Characteristics
Stainless steel is an alloy of iron, chromium (minimum 10.5 per cent) and typically nickel, molybdenum and other elements depending on the grade. The chromium content forms a self-repairing passive oxide layer on the surface that provides excellent resistance to corrosion and staining.
The most commonly fabricated grades in Australia are 304 (general purpose, suitable for most indoor and mild outdoor environments) and 316 (marine grade, with added molybdenum for superior resistance to chloride corrosion). Both are austenitic grades, meaning they are non-magnetic in the annealed condition and have excellent formability.
Advantages
- Corrosion resistance: outstanding resistance to rust, staining and chemical attack, often eliminating the need for protective coatings
- Hygiene: smooth, non-porous surface that is easy to clean and sterilise, making it the standard material for food processing, pharmaceutical and medical equipment
- Appearance: attractive natural finish (brushed, polished or satin) that does not require painting
- Strength: higher tensile strength than mild steel in most grades, particularly in work-hardened conditions
- Longevity: extremely long service life with minimal maintenance, which can offset the higher initial cost over the lifetime of a product
Limitations
Stainless steel is significantly more expensive than mild steel—typically two to three times the material cost. It is harder and more abrasive on tooling, which increases cutting and machining costs. Welding requires more care, with proper shielding gas (argon or argon-helium mixtures) and techniques to avoid sensitisation and discolouration. It also work-hardens quickly, which can make forming and machining more challenging if not managed properly.
Best Applications
Food and beverage processing equipment, commercial kitchens, marine hardware, balustrades, medical devices, chemical handling, water treatment, architectural features and any application where corrosion resistance, hygiene or aesthetic finish is a priority.
Aluminium
Properties and Characteristics
Aluminium is a lightweight, corrosion-resistant metal with a density of approximately 2,700 kg/m³—roughly one-third the weight of steel. Common fabrication grades include 5052 and 5083 (marine grades with excellent corrosion resistance and good formability) and 6061-T6 (a heat-treated structural grade with higher strength).
Aluminium naturally forms a thin oxide layer that provides good corrosion resistance in most environments. This can be enhanced through anodising, which thickens the oxide layer and allows for colour dyeing.
Advantages
- Weight: approximately one-third the weight of steel, making it ideal for applications where weight reduction is critical
- Corrosion resistance: good natural corrosion resistance that can be further enhanced through anodising
- Strength-to-weight ratio: structural grades such as 6061-T6 offer strength comparable to mild steel at a fraction of the weight
- Conductivity: excellent thermal and electrical conductivity, approximately 60 per cent that of copper at a much lower cost and weight
- Recyclability: aluminium is infinitely recyclable with no loss of properties, and recycling requires only 5 per cent of the energy needed to produce primary aluminium
Limitations
Aluminium is softer than steel, which means it scratches and dents more easily. It has a lower absolute strength than steel (though the strength-to-weight ratio is excellent), so thicker sections may be required to achieve equivalent structural performance, partially offsetting the weight saving. Welding aluminium requires specialised equipment (typically AC TIG or pulsed MIG) and greater operator skill. The material cost per kilogram is higher than mild steel, though the lower density means you need less material by weight for a given volume of parts.
Best Applications
Transport and vehicle bodies, marine components, aerospace, signage, architectural cladding, heat sinks, electronics enclosures, food-grade applications, outdoor furniture and any application where minimising weight is a primary objective.
Comparison at a Glance
The following summary highlights the key differences across the most important selection criteria:
- Cost (material): Mild steel is the most affordable, followed by aluminium, then stainless steel
- Weight: Aluminium is lightest (2,700 kg/m³), followed by steel and stainless steel (both approximately 7,850–8,000 kg/m³)
- Corrosion resistance: Stainless steel offers the best all-round corrosion resistance, followed by aluminium, then mild steel (which requires protective coatings)
- Strength: Stainless steel is generally strongest, followed by mild steel, then aluminium (though aluminium has the best strength-to-weight ratio)
- Weldability: Mild steel is easiest to weld, stainless steel requires more care, and aluminium requires specialised equipment and skills
- Appearance: Stainless steel offers the best natural finish, aluminium can be anodised for a range of finishes, mild steel requires coating for both protection and appearance
Making Your Decision
In practice, the right material choice is driven by the specific demands of your application. Start by identifying the non-negotiable requirements: Does the component need to resist corrosion without coatings? Must it be lightweight? Is it food-grade or medical-grade? Does it need to be welded on site? What is the budget?
Once you have established the critical requirements, the material choice often becomes clear. In many cases, mild steel with an appropriate protective finish provides the best combination of performance and value. Where corrosion resistance or hygiene is paramount, stainless steel is the answer. And where weight is the driving factor, aluminium is the logical choice.
At Alliance Metal Solutions, our team works with all three materials daily and can advise on the best option for your specific application. We offer complete sheet metal fabrication services across mild steel, stainless steel and aluminium, from laser cutting and CNC bending through to welding and finishing.
Need help choosing the right material for your project? Get in touch with our team for expert advice and a no-obligation quote.