10 10 月, 2026
Solar Mounting Steel: Grades and Coatings Buyers Need
A solar array is a long-life structure, and the steel holding it up spends that life outdoors — in sun and rain, in coastal salt or desert dust, under wind and sometimes snow load. Two decisions carry most of the risk: the section the design calls for, and the corrosion system protecting it. This note covers the steel a mounting system is built from, the grades it comes in, and the coatings that decide whether it outlasts the warranty.
Short answer
Solar mounting steel is judged on two things: the section has to carry the load, and the coating has to survive the site. The sections are ordinary structural and cold-formed products — rails, purlins, posts and brackets — in the same structural grades used in general fabrication. What separates a mounting order from an ordinary steel order is the corrosion system, because a mounting structure is thin-walled, fully exposed and hard to repaint.
Where the steel goes
| Component | Typical section | What it does |
|---|---|---|
| Mounting rail or torque tube | Cold-formed C, Z or hat section | Carries the modules and ties the array together |
| Post or foundation bracket | Tube, angle or a driven section | Transfers load to the ground and takes the moisture |
| Purlin or cross-member | Cold-formed C or Z purlin | Spans between posts and supports the rail |
| Clamp and fastener | Formed plate, often stainless | Holds the joint, and corrodes first |
The sections are usually cold-formed and thin, which is why the coating, not the mass of steel, carries most of the durability.
Grades: which family the steel comes from
Mounting steel is ordered in the same structural grade families as general fabrication, and the family name depends on the standard system the buyer works in. In practice a buyer meets the Chinese GB grades such as Q235B and Q355B, the European EN grades such as S235JR and S355JR, and the US ASTM grades such as A36 and A572. The equivalence between these families is the first thing to check, because the same letters and numbers are not used the same way in every system.
- The grade is chosen for the load and the section thickness, and ordinary structural grades cover most designs
- The designations differ between systems, so the equivalence should be read rather than assumed
- On thin cold-formed sections the coating usually decides, because outdoor failure is more often corrosion than yield
Coatings: the part that decides the service life
The coating decides whether a structure reaches the end of the array’s life or is repaired early. Each family protects the steel differently, and suits a different environment.
| Coating | How it protects | Where it suits |
|---|---|---|
| Hot-dip galvanized | A zinc layer that sacrifices itself at cut edges and scratches | General outdoor and inland sites; the default for structural sections |
| Zinc-aluminium coated | An alloy layer that holds up in some atmospheres and at higher temperature | Longer-life and warmer or more exposed sites |
| Pre-painted or colour-coated | A paint film over a metallic coating, for appearance as well as protection | Visible structures and sites where colour is specified |
| Stainless steel | An alloy that resists corrosion without a sacrificial layer | Coastal and high-chloride sites, usually for fasteners |
The coating is specified as a type and a coating mass, and the mass is what a buyer should compare between offers, because one coating name can hide a wide range. The environment — distance from the sea, rainfall, pollution, temperature — decides how much the site needs.
What to write in the order
Mounting orders go wrong at the coating and the environment, not at the grade. Settle these in writing:
- The section and the grade, and the standard system the grade is written in
- The coating type and the coating mass the environment requires, not a coating name alone
- The environment — inland, coastal or high-corrosion — and the expected life of the array
- The packing, because thin galvanized sections damage in transit and the damage is where corrosion starts
Send the product, the standard it must meet, the size, the quantity and the destination port, and the enquiry is worked against those points. See the steel product catalogue, how orders are inspected and certified, or request a quotation.
Related reading
Frequently asked questions
What steel is used for solar mounting structures?
Mainly cold-formed structural sections such as C and Z purlins, rails, torque tubes and posts. The sections are thin, so the coating usually decides how long the structure lasts.
Which grade is best for solar mounting steel?
The grade follows the load and the section thickness, and the structural grades in common use cover most mounting designs. Which designation applies depends on the standard system in the buyer’s market, so the equivalence should be checked rather than assumed.
Hot-dip galvanized or pre-painted steel for solar mounts?
Hot-dip galvanizing is the usual default for exposed structural sections, because it also protects cut edges and scratches. Pre-painted steel is chosen where appearance matters or where colour is specified.
Send the product, the standard it must meet, the size, the quantity and the destination port, and the enquiry is worked against those points. See the steel product catalogue, how orders are inspected and certified, or request a quotation.