Piston of internal combustion engine and a manufacturing method thereof

A method for manufacturing a piston of an internal combustion engine including a top surface having a coating composed of porous alumina,

• wherein the top surface includes:
• a first region that includes a part or all of a region connecting to an outer periphery of the top surface;
• and
• a second region that includes a part or all of a region inside the top surface,
• wherein the method includes the steps of:
• preparing the piston as a casting piston made of aluminum alloy of which the top surface is covered with a casting surface;
• removing the casting surface in the first region to expose a material surface of the casting piston, while the casting surface in the second region is not removed;
• and
• forming a porous alumina coating in the first and second regions by anodization of the casting piston including the exposed material surface, wherein an anodization condition for equalizing a height of the porous alumina coating in the first and second regions is predetermined such that the anodization occurs more rapidly in the first region where the casting surface has been removed than in the second region where the casting surface has not been removed and a top surface of the porous alumina coating in the first region after completion of the anodization is even with a top surface of the porous alumina coating in the second region.