Process Overview
Hot-dip galvanising is the dominant corrosion-protection technology for flat steel products — particularly for automotive body panels, construction cladding, domestic appliances, and HVAC components. The process applies a zinc (or zinc-alloy) coating to cold-rolled steel by passing a continuous strip through a bath of molten zinc at approximately 450–460 °C. The zinc metallurgically bonds to the steel surface through a series of iron-zinc intermetallic phases, providing both barrier protection and cathodic (sacrificial) protection that prevents underfilm corrosion.
A continuous hot-dip galvanising line (CGL or HDG line) processes cold-rolled, full-hard strip entering at one end and exits as coated, tension-levelled, and surface-treated coil at the other. Strip widths of 600–1,900 mm and thicknesses of 0.3–3.0 mm can be processed at line speeds of 60–180 m/min. A typical modern line produces 400,000–700,000 tonnes per year.
The line consists of several key sections: entry section (welder, strip accumulator), cleaning section (alkaline degreasing, brushing, rinsing), annealing furnace, zinc pot and wiping station, post-treatment (galvannealing, passivation, oiling), tension levelling, and the exit section (inspection, shearing, recoiling).
Full module access requires Pro
Pro subscribers get the complete module — all sections, key facts, glossary, and direct links to every global plant using this process.