| 摘要 |
PURPOSE:To increase lubricity and to enhance abrasion resistance, by applying anodic oxidation treatment on the upper circumferential surface including the top piston-ring groove of a piston made of an aluminum alloy including a large amount of silicon. CONSTITUTION:On the upper circumferential surface including the top piston-ring groove 6 of a piston 3 made of an aluminum alloy including a large a mount of silicon, alumite treatment is applied, while making the piston as an anode to form an alumite layer 14. Next, secondary electrolysis is carried out in the aqueous solution of metallic thiohydrochloric acid while making the piston 3 as an anode, so that the fine-grain crystal of metallic sulfide is crystallized and filled in fine holes 15 in the alumite layer 14. Thus, the lubricity on the sliding surface of the piston can be enhanced, and the biting and galling or the like can be restrained. |
