What This Group Covers
Corrosion is also the place where scale matters most, because the exposure is not uniform. A coastal site within a few kilometres of the sea, a fertiliser or cement plant, a saline-alkali soil and a clean inland plain all impose different corrosion loads on the same structure design.
- Hot-dip galvanizing to ISO 1461: zinc mass selection, coating thickness and what the standards actually require
- Zinc-aluminium-magnesium and other advanced metallic coatings, including self-healing behaviour at cut edges
- Aluminium alloys for racking, and how galvanic isolation should be handled at steel-aluminium interfaces
- Corrosivity classification by atmosphere and by soil, and why buried steel is a separate design problem
- C5 coastal, marine and high-salinity specifications, including duplex systems and stainless steel fasteners
- Fastener and small-component protection, which is where corrosion usually appears first
Three Configurations to Start From
Three protection strategies cover most exposure cases:
Standard HDG line
Hot-dip galvanized to ISO 1461, standard zinc mass for C2-C3 exposure. Best for: Inland, rural and light industrial sites. Relative cost: 1.0 (baseline).
Advanced coating line
ZAM or zinc-aluminium-magnesium with cut-edge protection. Best for: C3-C4 exposure, high humidity, cut-edge sensitive details. Relative cost: +6 to +14%.
C5 duplex line
Heavier zinc mass plus duplex coating, stainless fasteners, sealed interfaces. Best for: Coastal within a few kilometres, marine, high-salinity soil. Relative cost: +18 to +40%.
Why corrosion protection is demanding
Corrosion design is difficult because the input is a classification rather than a measurement, and because the cheapest specification always looks adequate until the first inspection. Getting it right requires a site-specific corrosivity assessment rather than a generic rural or industrial default.
- Atmospheric corrosivity varies enormously over short distances: marine exposure falls off sharply with distance from the shoreline, and local sources such as a cooling tower or a stack can dominate
- Buried steel corrodes by a different mechanism to exposed steel, driven by soil resistivity, moisture and chloride rather than by airborne deposition
- Cut edges, drilled holes and damaged coating are where corrosion starts, because they expose bare steel and defeat a coating designed for a continuous surface
- Galvanic corrosion at steel-aluminium interfaces and at stainless-steel-to-galvanized-steel joints is a design detailing issue that coating thickness cannot solve
- Fasteners and clamps are small, numerous and often specified late, and they are the components most likely to be under-protected
- Repair and re-coating on a live plant is far more expensive per square metre than the original coating, so the specification is effectively a one-way decision
Engineering Requirements
These are the inputs and detailing requirements we treat as mandatory for any project with a 25-year exposure assumption.
- Site-specific corrosivity classification for both atmosphere and soil, based on measurement or on documented local data rather than on a generic default
- Zinc mass specification per ISO 1461 for the section thicknesses and corrosivity category in use, stated in grams per square metre rather than left implicit
- Cut edge and drilled hole strategy: how the coating is protected where the steel is worked after coating, and which products offer edge protection without repair
- Galvanic isolation detailing at dissimilar metal interfaces, including insulating washers and sleeves where aluminium meets steel
- Fastener specification at the same protection level as the structure, with coating or alloy appropriate to the exposure class
- Drainage and detailing so that water does not stand against joints, crevices or ground contact zones
- Written first-maintenance interval by exposure class, supported by batch coating records so the interval is verifiable
Selection guidance: classify the site first, then choose the coating system. Applying a C3 specification to a C4 or C5 site is the most common and most expensive corrosion error in solar procurement.
Key Parameters
| Parameter | Typical specification |
|---|---|
| Atmospheric classes | C2 rural to C5 marine/industrial per ISO 9223; most solar sites fall in C2-C4 |
| Galvanizing standard | ISO 1461; typical minimum 85 um zinc for section thickness above 6 mm at C3 |
| Aggressive exposure | C5-M marine typically 140 um or higher plus duplex coating where specified |
| Advanced coatings | Zinc-aluminium-magnesium systems with self-healing behaviour at cut edges |
| Aluminium alloy | 6005-T5 or similar for rails where weight or chemical stability favours aluminium |
| Fasteners | Coated or stainless steel at a protection level matched to the exposure class |
| Buried steel | Separate design case driven by soil resistivity, moisture and chloride content |
| First maintenance | Stated interval by exposure class, backed by batch coating thickness records |
How We Deliver It
- Corrosivity classification produced for the specific site, separating atmospheric from soil exposure and identifying any local sources
- Coating system selected against the classification, with zinc mass stated in grams per square metre and verified by batch records
- Advanced metallic coatings considered where cut-edge protection and longer maintenance intervals justify the premium
- Galvanic isolation detailing at every dissimilar metal interface, including insulating washers, sleeves and gaskets
- Fastener specification set at the same protection level as the structure, not treated as a last-minute line item
- Detailing for drainage: joints and ground-contact zones designed so water does not stand and accelerate local attack
- Written maintenance interval with inspection criteria, so the durability assumption is auditable rather than implied
Standards and Compliance
- EN 1991-1-3 / ASCE 7 snow and ice load cases matched to your design return period
- IEC 61215 / IEC 61730 for module clamping zone and frame compatibility
- EN 1090 / AISC steelwork execution classes with weld procedure qualification records
- ISO 1461 galvanizing, ISO 12944 paint systems where duplex coating is specified
- ISO 9001 production quality management, batch traceability to heat numbers
- Local building code and permitting documentation support for your jurisdiction
Quality Assurance
Batch documentation is issued per lot: mill certificates traceable to heat numbers, galvanizing records with measured coating thickness, dimensional inspection reports from pre-assembly jigs and hardware lot traceability. Warranty covers named load cases and environmental exposure classes, so claims are settled against data rather than negotiation.
Installation and Site Productivity
The installation method is part of the technical proposal, not an afterthought. We state the equipment needed, the crew composition, the expected daily output and the tolerance acceptance criteria for every structural interface. Pre-assembled kits are labelled to your build sequence, fasteners are supplied in matched lots with torque values, and the design avoids site welding entirely. Where a project needs accelerated schedules, we plan multiple parallel work fronts and split kits accordingly.
Documentation You Receive
Documentation is built for audits, not decoration: structural calculation notes stating load cases and standards used; foundation design basis mapped to your geotechnical report; material certificates for steel and fasteners; galvanizing certificates with measured coating thickness per batch; assembly drawings with torque tables; and packing documentation matched to container manifests. For financed projects we add lender-format compliance statements; for public tenders we respond to documentation schedules line by line.
Cost and Commercial Considerations
- Coating typically represents 8-18 percent of structure cost, and upgrades add 6-40 percent depending on classification
- The cost difference between a correct C4 specification and a cheap C3 one is small compared with the cost of re-coating a live plant
- Stainless or coated fasteners are a small absolute line item, but under-specifying them is the most common cause of early visible corrosion
- Duplex systems cost more up front and typically extend the interval to first maintenance by a factor of two or more
- Buried steel protection is frequently omitted from first estimates, yet soil corrosion can reduce foundation life below the array design life
Reference Benchmarks
- Coastal utility projects in the Gulf and South-East Asia where C4-C5 exposure made duplex coating and stainless fasteners a specification requirement rather than an option.
- Saline-alkali and tidal-flat projects in China where buried and partially buried steel required separate soil-side corrosion design.
- Industrial sites in Europe where stack emissions and chemical fallout pushed atmospheric classification above the regional default.
- Desert and high-humidity projects where dust deposition combined with condensation cycles produced corrosion behaviour that a dry-inland assumption would have missed.
Service Life and Maintenance Planning
Service life is a design output, not a promise. Zinc mass, fastener coating class, drainage detailing and dissimilar-metal isolation are selected against the corrosivity category of your site, and the expected first-maintenance interval is stated in writing. For aggressive environments we step the coating system up at design stage, which is always cheaper than a retrofit.
How We Control Delivery
| Stage | What we do | What you receive |
|---|---|---|
| Corrosivity assessment | atmospheric and soil classification established with data sources recorded | corrosivity report and classification statement |
| Specification | zinc mass and coating system stated in grams per square metre per component group | coating specification sheet |
| Material intake | steel and coating supplier certificates verified against the specification | mill certificates and coating supplier records |
| Production | coating thickness sampled per batch, cut edges and holes inspected | coating thickness log and edge treatment records |
| Pre-shipment | fastener and small-component protection verified against the exposure class | fastener lot records and packing list |
| Handover | first-maintenance interval, inspection criteria and touch-up procedure issued | durability and maintenance plan |
Send your site location and exposure data – we will return a corrosivity assessment, a coating specification and a maintenance interval basis.
Guides in This Group
Hot-Dip Galvanizing Specifications for Solar Racking
Zinc mass selection, ISO 1461 compliance and how to specify coating thickness properly.
ZAM Steel & Advanced Coating Corrosion Resistance
Zinc-aluminium-magnesium systems, cut-edge self-healing and where the premium is justified.
C5 Coastal & High-Salinity Corrosion Protection
Marine exposure, duplex systems, stainless fasteners and soil-side protection for buried steel.
Related Application Directories
This scale band is often combined with the following application groups, which cover terrain, land type and site conditions.
Frequently Asked Questions
How do we know which corrosivity category our site is?
What zinc mass should we specify?
Is ZAM coating worth the premium over galvanizing?
How should we handle steel-aluminium interfaces?
What maintenance interval should we plan for?
What We Need to Quote
- Site location and distance from the coast, plus any local industrial emission sources
- Soil resistivity and chloride data for any buried or partially buried components
- Required design life, maintenance access cost assumptions and any owner corrosion standard
- Fastener and small-component requirements, or agreement for us to specify them to match the exposure class
Talk to a Structure Engineer
Send your site data, target capacity and construction programme, and our engineers will return a structure concept, a quantity estimate and a costed supply package.
