Galvanic corrosion in solar racking: how to keep your roof from disintegrating

Galvanic corrosion happens when two dissimilar metals are in electrical contact with an electrolyte (rainwater). Invisible at first but can destroy your panel rack in years.

Worst metal pairs

Carbon steel + aluminum = VERY BAD. Galvanized steel + aluminum = bad but tolerable with interfaces. Stainless + aluminum = ok. Aluminum + aluminum = perfect. Standard panel frame is anodized aluminum to avoid internal issues.

Where it appears

Steel screws (unprotected) on aluminum frames. Copper ground strap directly on galvanized steel. Old racks with steel bolt + aluminum nut. Any bimetallic contact exposed to rain.

Visual symptoms

White-gray dust (aluminum oxide) at the joint. Screw keeps tightening (material disappearing). Brown rust spots on aluminum. Coastal climate: shows in 6-12 months. Dry interior: 5-8 years.

Prevention

1) Hardware ALWAYS stainless 304 or 316 (316 coastal). 2) Nylon or EPDM insulating washer between different metals. 3) Plastic separator sleeve in holes. 4) Ground strap always same material as racking.

Repair existing corrosion

Hardware: replace with 316 stainless. Aluminum pitted (cratered): apply zinc-based tape to halt the process. Perforated: replace section. DON'T paint over — corrosion continues underneath.

Most-affected climates

USA: Florida, South Carolina, California coast. EU: Atlantic and Cantabrian coast. Industrial with smog: 3× faster corrosion.

Combine with solar rack types.