Galvanised Steel
Steel sheet, pipe, or structural sections coated with a protective layer of zinc, applied by hot-dip galvanising or electroplating, to prevent rust in outdoor and structural applications.
Covered in 1 MetalsCost.com News Intelligence article, most recently on August 24, 2026.
Overview
Galvanised steel is ordinary carbon steel given a zinc coating that protects it two ways at once: as a physical barrier keeping moisture and oxygen away from the steel underneath, and as a sacrificial layer that corrodes preferentially if the coating is ever scratched, shielding the exposed steel from rusting at that spot. That second property is what sets galvanising apart from a simple paint or lacquer coating and is why galvanised steel holds up so much longer than bare steel in outdoor and industrial settings.
How It's Manufactured
The dominant method is hot-dip galvanising: cleaned and fluxed steel is dipped into a bath of molten zinc at around 450°C, where it reacts with the surface to form a series of zinc-iron alloy layers topped with a layer of pure zinc, then withdrawn, cooled, and often passivated to prevent white rust from forming during storage and transport. Flat sheet steel is usually galvanised continuously on a coil line running through a zinc bath and air knives that control coating thickness, while structural pieces, pipe, and fasteners are dipped as finished shapes in a batch process. Electro-galvanising, which deposits a thinner zinc layer electrolytically, is used where a smoother finish or a lighter coating is preferred over maximum corrosion resistance.
Byproducts
Zinc ash and dross — a zinc-iron intermetallic sludge — form on top of and settle at the bottom of the galvanising bath, and both are collected and typically sold back into the zinc-recycling supply chain rather than discarded. Spent pickling acid, used to clean the steel surface before dipping, requires treatment or acid regeneration, and flux residues from the pre-treatment stage are managed as process waste as well, with many modern plants recovering and reusing a portion of both.
Who Consumes It
Construction and infrastructure contractors are the largest buyers, along with structural-steel fabricators, roofing and cladding manufacturers, and the automotive industry, which uses galvanised sheet for body panels. Manufacturers of outdoor equipment, fencing, guardrails, and agricultural machinery round out the demand base, essentially anywhere steel has to survive years of outdoor exposure, and water-tank and storage-silo makers rely on it heavily as well.
Everyday Uses
Galvanised steel shows up in roofing sheets, garden and property fencing, outdoor stair and balcony railings, HVAC ductwork, and the corrugated sheds and carports common in many neighborhoods, as well as the corrosion protection built into the doors and underbody of most cars. Street lighting poles, safety barriers, and water storage tanks are typically galvanised too.
Industrial Uses
It's used for structural steel on bridges and buildings exposed to weather, transmission towers, highway guardrails and light poles, HVAC ductwork, agricultural equipment and grain-storage structures, and as the base feedstock for further-coated products such as pre-painted steel sheet used in appliances and building cladding.
