| 摘要 |
PURPOSE:To prevent the separation of a nickel plated layer due to an anodizing solution from occurring by masking an anodized layer and nickeling a top part after performing anodic oxidation treatment along a top ring groove since the top part has been masked first. CONSTITUTION:At the time of surface treatment for a piston 10, first of all, a top part 11 is covered with a cap type mask 20, while a first tubular mask 50 is installed on the circumference of a skirt part 12, and a projection 52 is engaged with a second ring groove 14 for positioning. In addition, a pin mask 30 is covered on a masking part C where a locking pin 16 is attached, while a spring 40 is fitted in a top ring groove 13. In this state, anodic oxidation treatment takes place and then a hard alumite layer 18 is formed in an unmasked part along the top ring groove 13. Afterward, the circumference of the skirt part 12 inclusive of the hard alumite layer 18 is covered with a second tubular mask and then electroless plating takes place and thereby a nickel plated layer 17 is formed in the top part 11. |
