Tinplate is one of the eco-friendly packaging materials that are available. Tinplate is steel sheets that are coated on both sides by tin. his combines the strength of steel with the resistance to corrosion and solderability of tin.
Steel which is used to make tinplate is light gauge low carbon. There are many important steps involved in its production which can influence tinplate’s properties.
Continuously cast steel slabs are used as they produce cleaner steel. These slabs are scarfed or cleaned to remove surface defects, then heated to 1200 to 13000C and rolled to produce thin gauge sheets
These sheets are cooled and cleaned of any oxide that is formed during pickling. Earlier acids were used; however, innovations have made this step acid-free and oil-free, and more environmentally friendly.
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The hot steel sheets are cooled by using water and lubricating oil, and undergo further rolling.
The cooling liquids are removed by using alkaline phosphates, silicates and sodium hydroxide and finally with hot air.
This step makes the steel soft and achieves the desired grain structure. Batch annealing produces deep-draw to hard and stiff steel that can withstand vacuum and pressures, so is best for making cans and bottles. Continuous annealing is a shorter process that gives smaller grained steel.
The soft steel after annealing is lightly rolled to produce sheets of the final desired thickness.
Sometimes instead of temper rolling, a second round of reduction is used to roll the steel. This produces sheets that are thinner and stronger. The sheets produced can be as thin as 0.14 – 0.24 mm, which makes them more attractive as packing material as it saves transport costs and reduces carbon emissions.
