Tin & Electrolytic Coating

Tinplate — electrolytically tin-coated cold-rolled steel — is the material of choice for food and beverage cans, metal closures, and aerosols. Its combination of excellent corrosion resistance, formability, solderability, and food-safe surface has made it the foundation of the global packaging industry for over 150 years. Approximately 17 million tonnes of tinplate is produced annually, with the coating process carried out on high-speed electrolytic tinning lines (ETL) operating at 400–700 m/min.

The electrolytic tinning process deposits tin from a stannous (Sn²⁺) sulphate or methane sulphonate solution onto a steel substrate using DC current. The thickness of tin deposited is precisely controlled by current density and line speed, typically achieving coating weights of 1.0–11.2 g/m² per side (equivalent to 0.14–1.55 µm). These extremely thin coatings — far thinner than hot-dip galvanising — are sufficient for food can applications because tin is genuinely non-toxic and forms a passive oxide layer in the presence of food acids.

The substrate for tinplate is a specific cold-rolled, batch-annealed (or continuously annealed), and temper-rolled product called blackplate. The steel composition is tightly controlled — very low carbon, sulphur, and phosphorus — to ensure formability and corrosion resistance of the final coated product. DR grades (Double Reduced) are ultra-thin-gauge tinplate produced by cold rolling twice without intermediate annealing, achieving gauges of 0.09–0.17 mm for lightweight can ends and easy-open lids.