Tinplate is sheet covered with a thin layer of tin. Before the advent of cheap mild steel the backing metal was iron. While once more widely used, the primary use of tinplate now is the manufacture of tin cans.
Tinplate is made by rolling the steel(or formerly iron) in a rolling mill, removing any scale (rust) by pickling it in acid and then coating it with a thin layer of tin. Plates were once produced individually (or in small groups) in what became known as a pack mill. In the late 1920s pack mills began to be replaced by strip mills which produced larger quantities more economically.
Formerly, tinplate was used for cheap pots, pans and other hollowware. This kind of hollowware was also known as tinware and the people who made it were tinplate workers.
For many purposes, tinplate has been replaced by galvanized (zinc-coated) vessels, though not for cooking as zinc is poisonous. Zinc protects iron electrolytically, that is, the zinc will oxidize and turn to a white powder to preserve the iron, whereas tin will only protect the iron if the tin-surface remains unbroken. This is why it is not safe to eat food from a rusty tin can.