The bimetal cylinder is composed of a normal metal material with a certain mechanical strength as the parent material, while the inner hole working face is composed of the pipe of a special alloy material protection layer.

This layer have a certain thickness and hardness of the alloy layer according to the different working conditions of its use, or have wear resistance effect, or have corrosion effect, or have the effect that is both wear resistance and corrosion resistance. The protective layer is evenly attached to the parent material, which is locked in the gold phase with the parent material and will not fall off, forming into a solid integral - bimetal cylinder.