Abstract: A component (17) made of an aluminum silicon cast alloy whose surface is at least partly subjected to an anodic treatment to produce an oxide layer, which component comprises, prior to the anodic treatment, a surface-proximate deformation zone (4) configured as a homogeneous zone in which the silicon is uniformly distributed in the .alpha.-mixed crystal (1) and due to this homogeneous mixing of aluminum and silicon, the differing electric conductivities of the original structural constituents (.alpha.-mixed crystal, eutectic) are replaced by a uniform electric conductivity so that uniform oxide layers can grow during the anodizing process.

Abstract: A master cylinder for a hydraulic friction clutch, said master cylinder being connected to a physically actuatable pedal by a piston rod (17) which is articulated in semi-shells (14) enclosed in a piston skirt bushing (10), an end of said piston skirt bushing (10) remote from the piston rod (17) being connected to a piston (7) which is longitudinally displaceable in a guide sleeve (96) of the master cylinder (1), an end face of said piston (7) delimiting a pressure chamber (8) wherein the semi-shells (14) fill an inner space of the piston skirt bushing (10) without play and comprise a cup-shaped recess (15) in which a ball head (16) of the piston rod (17) is retained by positive locking, the piston skirt bushing (10) forming a structural unit with the radially stepped piston (7).