C-steel, code letter D in the Material Code according to DIN 24 960. As a face material (e.g. 1.3505, hardened) it displays good sliding properties when running against carbon graphite and bronze. In the past few years C-steel has lost practically all significance as a face material on account of its poor resistance against corrosion and high costs of production. It has been replaced almost totally by cast Cr-steel and – in mass-produced seals – by aluminium oxide. C-steel continues to be used as a spring and/or construction material in mass-produced seals for sealing oils and other media which do not corrode C-steel.