Aluminium Vs Steel Solar Mounting: Which Is Better?

Choosing between an aluminium and a steel solar mounting structure isn’t just a materials question. It’s a site-specific engineering decision. Most comparisons published online treat this as a generic global choice, weighing weight against strength in the abstract. They rarely factor in South Africa’s coastal salinity, inland wind loads, or local steel and aluminium pricing. This article breaks down the real differences between aluminium and steel solar mounting structures, and where each one actually makes sense on African project sites.

Aluminium vs Steel Solar Mounting Structure: What Actually Differs

Aluminium and steel behave differently under load, in corrosive air, and in project budgets. A solar mounting material comparison that only looks at strength-to-weight ratios misses half the picture. Installers need to weigh corrosion resistance, transport costs, and installation labour too.

Axe Struct manufactures both aluminium and galvanized steel mounting systems for rooftop, carport, ground mount, and floating solar applications. That range gives direct, comparative insight into how each material performs in South African field conditions, not just on a lab datasheet.

Weight, Strength, and Corrosion Resistance

Aluminium is roughly a third the density of steel. That makes aluminium racking lighter to transport and easier to lift onto a roof. Steel, though, has higher raw strength and better load capacity per rand spent on material. Aluminium naturally forms a protective oxide layer, which gives it strong built-in corrosion resistance without extra coating. Steel needs a protective coating, usually hot-dip galvanizing, to reach a similar service life.

How Each Material Performs Under South African Conditions

South Africa’s climate varies sharply between regions. Coastal zones around Durban and Cape Town carry high airborne salinity that speeds up corrosion on unprotected or poorly coated metal. Inland regions face fewer salt-driven corrosion risks but often see stronger, more sustained wind loads across open ground-mount sites. A structure that holds up well in Gauteng may not last as long on the KwaZulu-Natal coast without a different coating specification or material choice.

Aluminium Solar Racking: Strengths and Limitations

Aluminium solar racking resists corrosion without relying on a coating that can wear down or get damaged during transport and installation. That makes it a dependable choice where ongoing maintenance access is limited or costly. It’s also lighter, which cuts handling time on rooftops and reduces the structural load added to an existing roof.

The trade-off is cost. Aluminium generally costs more per kilogram than steel in South Africa. Its lower raw strength also means installers sometimes need larger cross-sections to match a steel structure’s load capacity. For large-scale, high-tonnage projects, that price difference adds up quickly.

Where Aluminium Racking Performs Best

Aluminium racking suits rooftop residential and commercial installations, where weight savings matter and roof structures have defined load limits. It’s also a strong option for coastal installations, where salt-laden air would otherwise shorten a poorly protected steel structure’s life. Aluminium is a common choice for floating solar applications too, since these systems sit in constant, direct contact with water.

For broader context on how material choice shifts across the continent’s varied climates, see solar panel mounting materials for African sites.

Steel Solar Mounting Frame: Strengths and Limitations

A steel solar mounting frame offers higher load capacity than an equivalent aluminium structure, and it typically costs less per ton of raw material. That combination makes steel the default choice for large ground-mount arrays, where tonnage adds up fast and every rand per kilogram matters across the full array footprint.

The catch is that steel needs proper corrosion protection to last. Bare or poorly coated steel will rust, especially in humid or coastal air. Without adequate galvanizing, a steel frame’s lifespan can fall well short of its aluminium equivalent.

Hot-Dip Galvanizing and Long-Term Durability

Hot-dip galvanizing coats steel in a layer of zinc that protects it from corrosion for decades, provided the coating thickness meets recognised standards. Hot-dip galvanized steel structures are commonly rated for 25 or more years of structural life when the coating thickness and maintenance schedule meet SANS galvanizing standards. That durability, combined with steel’s lower material cost, is why large inland ground mount solar farms often use galvanized steel racking rather than aluminium.

For a closer look at the coating process and its impact on service life, see why galvanized steel structures last longer.

Cost Comparison: Local Steel and Aluminium Pricing in South Africa

Steel is generally cheaper per kilogram than aluminium in South Africa. That’s why it dominates large ground-mount projects, where the total tonnage of racking runs high. But raw material price is only one part of the lifetime cost.

Aluminium’s lighter weight can lower transport costs, especially on remote or hard-to-access sites across the wider African service region. It also usually needs less ongoing maintenance, since it doesn’t rely on a coating that can chip or wear.

Steel structures cost less upfront but carry the added expense of galvanizing. They may also need recoating or touch-up work over decades of service in harsh environments. For a large project, the true cost comparison has to account for transport, coating, installation labour, and expected maintenance, not just the sticker price of the raw metal. Buyers sourcing at volume should weigh these lifetime factors before committing to one material across an entire project.

Best Material for Solar Structure by Application

There isn’t a single best material for solar structure that suits every project. The right pv frame material in South Africa depends on where the array sits, how it’s mounted, and what loads it needs to carry.

Rooftop and Carport Mounting

Rooftop installations generally favour aluminium because of its lower weight and easier installation on existing roof structures. Carport structures, which combine a solar array with a parking canopy, can use either material depending on span length and expected load. For guidance on matching structural type to a commercial parking layout, see choosing a solar carport structure.

Ground Mount and Floating Solar

Ground mount arrays, particularly at utility scale, tend to favour galvanized steel because of its load capacity and lower cost per ton over large footprints. The piece on utility-scale ground mount racking systems covers how engineers design these systems for large sites.

Floating solar sits at the opposite end of the spectrum. Constant water contact and humidity make aluminium’s natural corrosion resistance a strong fit, as the resource on floating solar mounting structures outlines. For a full overview of how these categories fit together, see the guide to solar structure installation types.

How to Choose Between Aluminium and Steel for Your Project

Structural engineers generally recommend matching mounting material to a site’s specific wind load and corrosion class, rather than defaulting to one material for every project type. Use the following checklist as a starting point:

• Wind load zone: Check the wind rating for your site before finalising a design. See wind load ratings for mounting structures for regional guidance.
• Corrosion exposure: Coastal or high-humidity sites need either aluminium or heavily galvanized steel with a verified coating thickness.
• Budget and lifetime cost: Weigh raw material price against transport, coating, and maintenance costs over the project’s expected life.
• Project scale: Large ground-mount arrays generally favour steel’s cost-per-ton advantage; smaller rooftop or coastal jobs often favour aluminium’s low maintenance needs.

Neither material is universally better. Aluminium and galvanized steel each have a place, depending on the application, the site’s exposure, and the scale of the project. Installers, EPC contractors, and wholesalers planning a project in South Africa or elsewhere across the region can contact Axe Struct’s engineering team for a material recommendation matched to their site conditions and load requirements. For bulk or wholesale orders, see the page on sourcing mounting hardware in bulk.