A larger amount of refractory film (0.05 mm thick), which serves to protect the surface of the hardened component against the undesirable effects of air during heat treatment in the furnace without a protective atmosphere.

It can be used for most hardenable steels, with the best results achieved for steels with higher carbon content, chromium and self-hardening steels.

The operating temperature range is from 750°C when the spontaneous neutralization of residual air begins to about 1150°C, above which the life of the foil is shortened.

Can also be supplied in lengths of 0.5m or longer than 1m. It is advisable to use gloves when wrapping the foil, the edges are very sharp. Wrap the material before hardening and fold the edges of the foil several times, it is advisable to wrap a piece of paper inside the foil. When it burns, it burns off oxygen, which is unfavourable and causes scale to form.