Rust returning on a repainted structure

Safety first. The structure is bonded to earth and carries DC cables that are live whenever there is daylight. Do not grind, wire-brush hard, drill or weld near the panels yourself: sparks and tools can damage cables and connectors. Do not climb an elevated frame. If you ever feel a tingle when touching the structure, stop and read current in the solar structure, then call a qualified engineer.

What solar structure rust means

Most solar stands in Punjab are galvanised steel: steel coated with zinc, which corrodes slowly to protect the steel underneath. Rust appears where that zinc is missing, thin or used up. You will usually see one of four things:

• White or grey powder on galvanised steel. Zinc oxidising where water lingers or parts were stored wet. Usually cosmetic at first.
• Red-brown rust at cut ends, welds and holes. Site cutting, welding and drilling remove the zinc; uncoated spots rust first.
• Rust on bolts, nuts and clamps. Plain or poorly plated fasteners rust long before galvanised sections do.
• Rust under or around base plates. Ponding keeps the plate and anchor wet for days after rain.

Our solar structure design process explains why coatings and fixings are part of the design, not an afterthought.

Quick-check table: is this rust serious?

Galvanised structure rusting: why it happens

Properly hot-dip galvanised steel should resist rust for a long time in normal Punjab conditions. Early rust usually has one of these causes:

1. Thin or patchy coating. Electro-plated or "painted galvanised" steel carries much less zinc than hot-dip galvanising. It can look the same on the day of installation.
2. Unprotected site work. Every cut, weld and drilled hole made on the roof breaks the coating. Industry guidance on repairing galvanised steel names zinc-rich paint, zinc solder or sprayed zinc as acceptable repairs, applied to clean, dry steel. Ordinary paint alone is not the same thing.
3. Water that never drains. Base plates in drain lines, low frames that trap dust and leaves, and cable trays lying flat on the roof hold moisture against the steel. Frame type affects this; see L2 vs L3 vs elevated solar structures and our roof waterproofing guide.
4. Mixed metals. Different metals touching in the presence of moisture can set up galvanic corrosion, where one corrodes faster. Isolating washers and coatings prevent it.
5. Aggressive air. Sites near dyeing units, chemical processes or smoky industrial chimneys, common around Faisalabad's industrial areas, corrode steel faster than a quiet residential roof.
6. Bird droppings and nests. They hold moisture and dirt against the frame. See pigeons and birds under solar panels.

Rust on solar panel frame: what it really is

Solar panel frames are aluminium, which does not form red rust. Brown marks on a panel frame almost always come from a rusting steel clamp, steel bolts or washers, or tiny steel filings left after drilling, which rust in the first rain and leave orange dots.

It is usually cosmetic, but a rusting clamp can lose grip. Manufacturers also forbid drilling extra holes in the panel frame, as it can cause corrosion and may affect the warranty. Have corroding clamps replaced, not painted over. For clamps that have already loosened, see solar panels loose or moving in wind.

Safe owner checks

Do these on a calm, dry day, from the roof surface only, without touching cables or connectors.

1. Walk the rows and look at each base plate, column foot, weld and cut end you can see.
2. Photograph every rust spot, close up and from a distance, to compare later.
3. Check after rain where water stands around plates, rails or cable trays. Mark those spots in your photos.
4. Clear drains and spouts and sweep dust, leaves and plastic from under low frames, keeping clear of cables.
5. Look at the bolts and clamps from a safe position. Note any that look loose, thinned or missing. Do not tighten clamps on the panels yourself.
6. Note the earthing connection at the frame if you can see it. A green-brown crusted joint should be checked by an engineer.
7. Send the photos to your installer with your system details, and the roof location of each spot.

Do not sand, grind or paint near DC cables and connectors, and never stand on rails or panels or climb an elevated frame.

What an engineer will check

An engineer decides whether the rust is cosmetic or structural, and why it started:

• Section loss. How much steel is left at the worst points: columns, base plates, anchor bolts and bracing. Members that have thinned are replaced, not painted.
• Anchors. Rusted anchor bolts lose holding power and may need replacing, with the plate resealed. See roof load and structural checks explains why anchoring matters.
• Fasteners and clamps. Replacing plain bolts with properly coated or stainless fasteners, with isolating washers where metals differ.
• Coating repair. Cleaning the area to sound steel, then applying a zinc-rich repair coating to the right thickness.
• Earthing continuity. Rust at bonding points can raise earth resistance, so joints are cleaned, remade and tested. See solar earthing and surge protection.
• Drainage and layout. Raising base plates on sealed plinths, re-routing cable trays and moving anything sitting in water. If rust is linked to water coming through the roof below, see roof leaking after solar installation.
• Wind safety. Whether the weakened frame can still carry storm loads before repair; see our storm and lightning safety guide.

Work near the panels is done with the system safely isolated following the inverter manufacturer's shutdown sequence.

How to prevent solar stand rust

At design and installation:

• Use hot-dip galvanised sections suited to the site, and say so in the quotation.
• Protect every site cut, weld and hole with a zinc-rich repair coating.
• Use coated or stainless fasteners with the right washers, and isolate dissimilar metals.
• Keep base plates out of drain lines and lift them on sealed plinths where water collects.
• Lift cable trays off the roof surface so water drains under them.
• On sheet roofs, fix into sound purlins and seal around fixings; see solar on tin and metal sheet roofs.

Every year: inspect before the monsoon and after major storms, clear drains and debris under frames, and touch up early rust before it spreads. Our annual solar maintenance checklist puts these checks together.

Warranty and service at Solar Works Pakistan

Structures we design and install carry a 3-year Solar Works Pakistan structure warranty; after that period, the customer is responsible for appropriate maintenance. Our 1-year service warranty applies under the applicable project terms. Once a complaint is registered, we target sending service personnel within 48 hours to begin diagnosis; repair time depends on what is found. See how after-sales service works.

We can also inspect structures installed by other companies across Punjab and advise on repair or replacement, as a chargeable service.

Frequently asked questions

Why is my solar structure rusting after one year?

Usually because cut ends, welds or holes were not re-coated, fasteners were plain steel, water ponds around base plates, or the coating was thinner than true hot-dip galvanising. Photograph the spots and ask your installer to inspect them.

Is rust on a solar stand dangerous?

Surface rust is an early warning, not an immediate danger. Rust that has flaked, made holes, or eaten into bolts, base plates or columns reduces the frame's strength against storm winds. Have that checked before the next storm season.

Can I paint over rust on my solar structure?

Ordinary paint over rust rarely lasts. The rust needs cleaning back to sound steel and a zinc-rich repair coating, and work near the panels needs the system safely isolated. Leave anything near cables, connectors or the panels to an engineer.

How do I remove rust on solar panel frame?

Panel frames are aluminium and do not rust red. Brown marks usually come from a steel clamp or bolt, or filings from drilling. Do not scrape or drill the panel frame; have the corroded clamp or bolt replaced instead.

Can I scrape rust off the solar panel frame?

No. Do not scrape, sand or drill the panel frame. The rust is coming from a steel part, so have that clamp or bolt replaced by your installer.

Does the structure warranty cover rust?

Solar Works Pakistan gives a 3-year structure warranty on structures it designs and installs; after that, maintenance is the customer's responsibility. Ask for the written terms with your quotation.

Sources

1. American Galvanizers Association, "Repairing coating damage after delivery to a jobsite" (accepted repair methods for damaged galvanised coatings)
2. American Galvanizers Association, "Wet storage stain vs. white rust" (white oxide on galvanised steel stored or kept wet)
3. The Construction Specifier, "Avoiding galvanic corrosion with dissimilar metals" (causes and isolation methods)
4. JinkoSolar Global Installation Manual (2026), sections on frame drilling, anti-corrosion bolts and regular inspection: https://www.jinkosolar.com/uploads/[FINAL] JinkoSolar Global Installation Manual_202605_A1.8-EN.pdf