Galvanizing

Galvanizing coats steel in zinc for long-term, low-maintenance corrosion protection. It's the standard for outdoor structural steel because the zinc protects two ways at once — as a barrier and sacrificially — in a way paint alone can't. This overview covers the methods and standards; the deep guide below has the coating-thickness and lifespan numbers.

The methods

• Hot-dip galvanizing — steel is cleaned and immersed in molten zinc (~450°C); the zinc reacts with iron to form a bonded zinc-iron alloy coating. The workhorse for structural steel. Limited by kettle size.
• Thermal spray (metallizing) — molten zinc or zinc-aluminum is sprayed onto the surface; works on-site and on parts too large to dip, and for touch-up of welds and cut ends.
• Electro-galvanizing — a thinner electroplated zinc layer for indoor/light-duty parts.

How it protects — barrier + sacrificial

The zinc seals the steel from moisture and oxygen (barrier), and where the coating is scratched or cut, the surrounding zinc corrodes preferentially to protect the exposed steel (sacrificial / cathodic). That cut-edge protection is what sets galvanizing apart from a barrier-only paint film.

Methods at a glance

Standards & where it's used

Hot-dip galvanizing follows ASTM A123 (structural steel — minimum thickness by steel section) and ASTM A153 (fasteners and hardware). It's used on structural steel, bridges and highway hardware, transmission and utility structures, agricultural and outdoor equipment, and fasteners.

Related guide & next step

• Coating thickness, lifespan by environment, and vs paint/powder → hot-dip galvanizing guide
• What it costs per pound, per ton and per sq ft → hot dip galvanizing cost
• Corrosion + fire on structural steel → structural steel coating
• Find a contractor → industrial coating contractors

Need steel galvanized or a duplex system specified? Get a free quote with your part and its service environment, and we'll match a contractor for it.