The chrome layer acts as corrosion barrier. The oxide layer recues chrome surface oxidation and covers discontinuities in the surface. The process was developed in Japan and one version, known as Hi-Top is being made in the United Kingdom.
The chromium/chromium oxide layer is even thinner than the thinnest tin coatings normally used, and must be lacquered before it can be used in the manufacture of containers.
The cost if tin-free steel is lower than of tinplate, but is increased by the necessity for lacquer coating.
Tin-free steel has found fairly wide usage, typically examples being daw-redraw containers and fixed ends for processed food cans.
Tin-free steel
