A utility-scale solar farm is thousands of tons of galvanized and carbon steel staked into the desert — and in the Southwest, that steel bakes, freezes overnight, and gets sandblasted by monsoon dust year after year. When a 60 MW Arizona installation found white rust and edge corrosion spreading across tracker torque tubes and racking near grade, the operator needed a recoat that protected the asset without taking blocks offline during peak generation season. This case study covers how the work was scoped, prepped, coated, and scheduled around 115°F afternoons.
Quick Answer
Corroding solar structural steel can be recoated in the field by zoning the array, abrasive-blasting or power-tool-cleaning to the right surface profile, and applying a desert-rated system — typically an inorganic zinc or zinc-rich primer, an epoxy intermediate, and a UV-stable polyurethane topcoat — while scheduling application around surface temperature and dew point. The Arizona project recoated the worst tracker and racking steel block-by-block during live generation with no lost production days.
Key Takeaways
| Challenge | Approach | Result |
|---|---|---|
| Live generation, no full outage | Block-by-block zoning around tracker rows | Zero lost production days |
| White rust on galvanizing + edge corrosion | Surface prep to spec profile per SSPC/AMPP | Sound substrate for recoat |
| 115°F steel, low humidity, dust | Apply by surface temp/dew point; dawn windows | In-spec cure, no solvent boil/dry spray |
| Long asset life expectation | IOZ/zinc-rich → epoxy → polyurethane stack | Restored multi-decade corrosion protection |
Three-Coat Desert Steel System
The Challenge
The array’s tracker torque tubes, bearing assemblies, and racking legs near grade showed two problems: white rust on galvanized surfaces (zinc oxidation accelerated by trapped moisture and dust) and red-rust edge corrosion where galvanizing was thin or damaged during install. Left alone, section loss at connections threatens tracker reliability. A full outage was off the table during peak generation, and the steel itself was reaching 110–120°F by midday — outside the application window for most coatings.
The Approach
1. Zone the array, not the whole site
Work was sequenced block-by-block along tracker rows so only a small fraction of the array was ever in work. Crews coordinated with O&M to stow trackers in the work zone while neighboring blocks kept generating — the same live-operations logic behind our warehouse and data-center zero-downtime work.
2. Prep to the right profile
White rust and contamination were removed and the surface brought to the specified cleanliness and anchor profile using abrasive blasting where access allowed and power-tool cleaning at tight connections, following SSPC/AMPP surface-prep standards. Profile and soluble-salt checks gated coating — recoating over compromised galvanizing without prep is the classic way to buy a second failure, as covered in our industrial coatings guide.
3. Specify for the desert
The system was a zinc-rich/inorganic-zinc primer for galvanic protection, an epoxy intermediate for barrier and build, and a UV-stable polyurethane topcoat for the relentless Southwest sun — the same class of stack used on bridge and infrastructure steel and power-generation assets.
4. Beat the heat with the clock
Application followed steel surface temperature and dew point, not the wall clock. Crews worked dawn and early-morning windows when steel was within spec, avoiding the midday heat that causes solvent boil, dry spray, and premature skinning. Dust control and inter-coat timing were managed to the manufacturer’s data sheet.
Results
- Zero lost production days — generation continued block-by-block throughout.
- Corrosion arrested on tracker and racking steel; connections returned to sound condition.
- Restored multi-decade protection with a documented, inspectable three-coat system.
- A per-block QA log (profile, DFT, conditions) became the operator’s as-built corrosion record — feeding the kind of inspection cadence in our commercial tank inspection approach.
Copy the method, not the anecdote
Another Southwest array can reuse the sequence only if the same constraints are written into the spec. Tracker rows sit close to the ground, so blast and spray access is a crawl, not a scaffold bay, and containment has to keep grit out of torque-tube bearings and drivetrains. Collection cable and tracker motors stay energized in the blocks that are still generating. The work permit should name who stows and isolates the row and who confirms that isolation before blasting starts.
Hold the coating window to the data sheet. Desert steel that is in spec at dawn is often out of spec by mid-morning, and a monsoon week can wipe out that window with dew and dust. Build float into the block schedule for those mornings instead of pushing application onto hot steel to stay on the plan. Solvent pop, dry spray, and dust in the wet film show up later as edge rust, which is the defect this project was hired to stop.
Close each block with the same record: cleanliness and profile, soluble salts, steel temperature and dew point at application, and dry-film thickness per coat. That packet is what the next operations contractor will have when the polyurethane chalks. Without it, the array is back to recoating on guesswork.
Facility Manager Checklist
- Map corrosion before scoping: Distinguish white rust on galvanizing from red-rust section loss; prioritize connections.
- Zone around generation: Stow and isolate trackers block-by-block so the array stays live.
- Prep to spec: Hit the specified profile and check soluble salts — never recoat over compromised galvanizing blind.
- Schedule by surface temp/dew point: Use dawn windows; keep steel within the coating’s application range.
- Document per block: Log profile, DFT, and ambient conditions as the asset’s corrosion-control record.
Frequently Asked Questions
Can solar structural steel be recoated without shutting down the farm?
Yes. By zoning the array and stowing trackers block-by-block, crews recoat the worst steel while neighboring blocks keep generating — as in this project, which had zero lost production days.
What coating system suits desert solar steel?
A zinc-rich or inorganic-zinc primer for galvanic protection, an epoxy intermediate for barrier/build, and a UV-stable polyurethane topcoat for the Southwest sun — applied over properly prepared, profiled steel.
How is extreme heat handled during application?
By scheduling to steel surface temperature and dew point rather than the clock — typically dawn/early-morning windows — to avoid solvent boil, dry spray, and premature skinning that 115°F midday steel causes.