Case: Corrosion-Resistant Fasteners for a Utility-Scale Solar Project in Spain (Zn-Al-Mg & A4-80)

Case summary: YPFasteners supplied corrosion-resistant fastener packages for a utility-scale solar PV project in southern Spain. The order combined Zn-Al-Mg coated Grade 8.8/10.9 structural bolts for fixed-tilt and tracker frames, A4-80 (AISI 316) stainless fasteners for pivot joints and sensor attachments, and pre-applied anti-galling treatment on stainless threads. Grade 10.9 parts were coated with a hydrogen-embrittlement-controlled process to avoid hydrogen charging. Salt-spray performance was verified to 1,500+ hours per ISO 9227, and every batch shipped with full traceability and test reports. The project recorded zero corrosion-related non-conformities during the 18-month construction phase.

Project Background

The site is a 150 MWp utility-scale solar plant on a high-plateau location in southern Spain, where summer UV exposure is intense and winter nights bring frost and condensation cycles. The mounting-system OEM specified corrosion protection beyond standard galvanizing because the project owner required a 30-year design life for the tracker and fixed-tilt structures.

The fastener scope covered the full mounting system: main structure connections, tracker pivot joints, module clamps, and accessory attachments. Three corrosion classes were present in different zones, so the OEM chose a two-material strategy rather than a single coating across the board.

The Challenge

• Two corrosion environments on one site. Main structural connections sit above the module plane with good drainage — suitable for Zn-Al-Mg coated carbon steel. Pivot joints and small attachments are in contact zones, crevices, and shaded areas where condensation persists — those required A4-80 stainless to avoid crevice corrosion.
• Stainless thread galling during installation. A4-80 stainless fasteners installed at high volume on site tend to gall and seize, especially in dry climates with fine dust. The OEM needed a solution that did not rely on site-applied lubricant (which is inconsistently applied and attracts dust).
• Salt-spray verification. The owner's specification demanded documented corrosion performance — not just material grades — with salt-spray test evidence per ISO 9227.

What We Supplied

• Zn-Al-Mg coated structural bolts, Grade 8.8 and 10.9 — M12, M16, and M20 for frame and tracker main connections. Zn-Al-Mg (zinc-aluminum-magnesium) coating provides enhanced cut-edge protection compared with conventional zinc coatings. High-strength Grade 10.9 parts were coated with a hydrogen-embrittlement-controlled process (non-electrolytic zinc-flake or acid-free treatment per ISO 10683) to avoid hydrogen charging; salt-spray resistance verified to 1,500+ hours without red rust per ISO 9227.
• A4-80 (AISI 316) stainless steel fasteners — for pivot joints, hinge pins, sensor brackets, and small attachments: hex bolts, screws, and nut-washer sets.
• Anti-galling surface treatment on stainless threads — a pre-applied, PTFE-based dry-film lubricant layer (e.g., Xylan or equivalent) on the threads of A4-80 parts, verified with assembly-and-disassembly torque tests on the supplied batch to confirm consistent low friction without site-applied lubricant.
• Washers and locking hardware — hardened washers for structural connections and split or nylon-insert lock nuts where the OEM specified vibration resistance.
• Documentation package — EN 10204 3.1 certificates, material chemical composition, mechanical property reports, salt-spray test reports, and anti-galling torque test data.

Manufacturing and Quality Control

• Material segregation: Zn-Al-Mg coated carbon steel and A4-80 stainless were produced and packed in separate, color-labeled lots to prevent mix-ups on site.
• Coating control: Zn-Al-Mg coating thickness and adhesion were verified per batch; salt-spray coupons were tested from the production lot, not from a pre-certified sample.
• Thread protection: stainless threads were masked before any secondary processing; the anti-galling layer was applied under controlled conditions with batch-level torque verification.
• Packaging for coastal transport: components were wrapped in VCI (vapor corrosion inhibitor) paper with desiccant, and pallets were labeled by zone (structure vs tracker vs accessories) to match the site installation sequence.

Delivery and Results

• Quantity: 186,000 pieces across 34 line items (structure, tracker, and accessory packages).
• Lead time: 4 weeks from order confirmation to shipment; partial deliveries were scheduled to match the site's installation sequence.
• Site result: the project recorded zero corrosion-related non-conformities during the 18-month construction phase; no galling issues reported across the stainless fasteners.
• Owner approval: the salt-spray and anti-galling documentation was accepted without follow-up queries.

Why This Order Worked

The OEM's engineering team selected us because we provided the two-material strategy as a complete package: Zn-Al-Mg structural bolts, A4-80 stainless for critical zones, and pre-applied anti-galling treatment — all with production-lot test evidence. Having one supplier for the full fastener scope removed the risk of inconsistent coating standards across multiple vendors.

Ready to Spec Fasteners for Your Solar Project?

If your solar project needs corrosion-resistant fasteners with documented performance, send us your BOM and the site's corrosion classification. We will confirm the material and coating strategy (Zn-Al-Mg, HDG, A4-80/A2-70 stainless), the test plan (salt-spray, anti-galling), and delivery scheduling — typically within 24 hours.

• Need a material/coating comparison for your site conditions? Ask for our corrosion fastener selection table.
• Need salt-spray or anti-galling test data? Request sample test reports from a comparable project.
• Need a full BOM review? Send your mounting-system drawing and we will confirm feasibility and lead time.