Galvanised coil, formally known as galvanised steel coil, refers to a metal composite material with exceptional corrosion resistance. It is produced by uniformly coating the surface of a cold-rolled or hot-rolled steel substrate with a layer of metallic zinc through specific galvanising processes (such as hot-dip galvanising or electrogalvanising). This material is typically supplied in coiled form. The core performance of galvanised coil hinges upon both the substrate and the zinc coating. Its production process involves multiple precision steps to ensure uniform coating distribution and strong adhesion: Key Production Processes (using mainstream methods as examples): Hot-Dip Galvanising (HDG): The most prevalent method, accounting for over 80% of production. Substrate Pre-treatment: Degreasing (removing oil residues), pickling (removing surface scale), rinsing (neutralising acid solution), and drying to ensure a clean substrate surface; Hot-dip galvanising: The pre-treated substrate is immersed in molten zinc at 440-460°C, where a chemical reaction forms a composite coating comprising an ‘iron-zinc alloy layer + pure zinc layer’; Post-treatment: Zinc layer thickness is controlled using an air knife (high-pressure nitrogen). The substrate is then cooled, passivated (optional, enhancing fingerprint resistance and white rust prevention), oiled (for rust prevention), and coiled into rolls.