Galvanizing & Corrosion Protection
CSI Division 05, Metals
A zinc coating applied to steel, most commonly by hot-dip galvanizing, dipping fabricated steel into molten zinc, to protect it from corrosion, used on steel that will be exposed to weather or moisture, such as exterior stairs, guardrails, and structural steel in coastal or industrial environments.
Why it matters
Galvanizing has to happen after fabrication, cutting, welding, or drilling a galvanized piece afterward breaks the coating and exposes bare steel at exactly that spot, so the fabrication sequence has to treat galvanizing as one of the last steps rather than something done to raw stock before fabrication.
On a real project
A fabricator completes all welding, cutting, and drilling on a set of exterior stair stringers before sending them out for hot-dip galvanizing, so the entire finished piece, including every cut edge and weld, gets fully coated.
Who this matters most to
An Ironworker or specialty installer sets the galvanized steel in the field, field-touching up any coating damaged during installation with a zinc-rich repair compound.
Where this goes wrong
An installer field-drills a bolt hole into an already-galvanized guardrail post to fit an unexpected field condition, exposing bare steel at the hole with no zinc coating protecting it. Rust begins forming at that exact spot within the first year, well before the rest of the galvanized piece shows any corrosion.