A light alloy piston for diesel engines includes a piston head coated with a hard annodized layer having a combustion chamber recess and/or a fuel-guiding channel provided adjacent to the edge of the combustion chamber recess and/or valve pockets. The piston head is free of a hard anodized layer in those regions which are highly stressed by gas and mass forces. Preferably those regions of the piston head adjacent to edge portions of the combustion chamber recess lying in the direction of the piston pin are free of a hard anodized layer.