An array engineered for 30 years of clean power can start visibly corroding within a single season if the metal-to-metal bonding underneath the panels was never done right — and by the time it’s visible, the damage is already structural.

What “Bonding” Means on a Solar Array

Bonding is the permanent joining of metallic parts into an electrically continuous path. Electrical bonding connects panel frames, racking, and enclosures to a grounding electrode system for lightning protection and shock prevention. Structural bonding is the mechanical attachment of modules to mounting rails, whether through clamps and bolts or specialized industrial adhesives. When either connection is weak, inconsistent, or built from incompatible materials, the result isn’t just an electrical hazard — it’s an ideal environment for accelerated corrosion.

The Corrosion Mechanism Behind Poor Bonding

The dominant failure mode here is galvanic corrosion, a distinct mechanism from the thermal-expansion-driven bond failure that affects the same racking joints: two dissimilar metals in electrical contact, with an electrolyte like rain, dew, or salt spray bridging them, cause one metal (the anode) to sacrifice itself while the other corrodes more slowly. Solar racking commonly mixes aluminum frames, stainless fasteners, and galvanized steel rails — aluminum, being more electrochemically active, is the one that pits, weakens, and eventually fails structurally if the bonding interface isn’t managed. Poorly bonded joints also leave microscopic gaps that act as capillaries, drawing in moisture and pollutants that form a concentrated electrolytic cell right where two metals meet.

Where Poor Bonding Actually Comes From

Improper torque is a leading cause — too loose and moisture enters the joint, too tight and it cracks the metal’s protective oxide layer and exposes bare substrate. Anodized aluminum frames need that protective, non-conductive layer physically “bitten” through by star washers or a specialized grounding clip for electrical bonding to work at all; skip that step and the resulting high resistance drives localized heating and faster oxidation. Incompatible material selection — zinc-plated steel screws directly against aluminum with no buffering — triggers rapid galvanic decay from the electrode-potential difference alone; stainless steel (Grade 304 or 316) or aluminum-rated coated fasteners avoid this. Coastal and other high-salt environments accelerate all of the above, since salt spray is an unusually efficient electrolyte that can produce visible white rust on aluminum within just a few years of a minor bonding flaw.

Why This Matters Beyond Aesthetics

Corroded bonding points raise electrical resistance enough to create hot spots in a high-voltage DC string, and in extreme cases drive arcing — a documented cause of solar-related fires. A compromised grounding path can also prevent safety breakers from tripping correctly during a fault, leaving structure energized. Mechanically, corrosion at the panel-to-rack bonding point thins and embrittles the metal, making structural failure during a wind or snow event significantly more likely. And electrically, rising resistance in the grounding network can trip modern inverters’ ground-fault detection circuits into nuisance shutdowns, creating downtime that has nothing to do with the panels themselves.

Prevention Strategies That Actually Work

Conductive adhesives are increasingly used in place of, or alongside, mechanical fasteners specifically because they bond continuously across the full joint surface rather than at isolated point-loads — sealing out the electrolyte that galvanic corrosion depends on, while also absorbing thermal expansion and reducing mechanical fatigue at the joint. Email Us to review conductive-adhesive options for a racking or grounding interface prone to galvanic mismatch. Material compatibility matters independent of adhesive choice: check the galvanic series before joining dissimilar metals, use an insulating barrier or sacrificial anode where full electrical bonding isn’t required, and specify UL-listed grounding lugs rated for the specific metal pairing (AL7CU/AL9CU ratings for aluminum-to-copper connections, for example). Calibrated torque wrenches and serrated flange nuts or dedicated grounding clips ensure the anodized coating is pierced correctly and consistently rather than by feel. In high-corrosion environments, an anti-oxidant joint compound at the bonding point — standard practice in industrial electrical work — keeps air and moisture from ever reaching the metal-to-metal contact, and for repairs on already-corroded joints, a fast-curing UV-cure adhesive minimizes how long a freshly cleaned contact point sits exposed before it’s sealed again.

Monitoring After Commissioning

Annual infrared thermography catches corroded or loose bonding connections as hot spots before they progress to fire risk or system failure. Continuity testing with a micro-ohmmeter measuring resistance between modules and the central ground point (industry practice generally targets under 0.1 ohms) reveals degradation well before it’s visible. Visual inspection for crevice corrosion — bubbling paint, white powdery deposits, rust streaks in the narrow gaps between fasteners and frames — should be part of any routine maintenance cycle, with affected components cleaned, treated, and re-bonded immediately when found.

The Return-on-Investment Case

Skipping quality fasteners or anti-oxidant treatment might save a modest amount on a multi-megawatt project up front, but the downstream cost runs higher: more O&M spend on emergency repairs, a shortened asset life (30 years of production versus 15), and, increasingly, insurance requirements that condition fire and wind coverage on documented proper bonding.

Conclusion

A solar array’s weakest connection determines its real service life more than any single premium component does, which is why bonding-related corrosion deserves the same engineering rigor as cell efficiency or inverter selection. Incure’s conductive and structural adhesive systems are formulated to seal out the moisture that drives galvanic corrosion at racking and grounding interfaces. Contact Our Team to discuss bonding and corrosion-prevention materials for a specific installation environment.

Visit www.incurelab.com for more information.