工艺中的 预镀为改善镀层与底金属之间的密着力，，以快速方式先镀上一层薄镀层，而使附着力增强。化学镍镀层均匀,不会因高低电流差,导致某些地方镀的比较厚,某些地方镀的比较薄.预镀就是打底 作比没做好 理由如上述
Class A – 0.0001 inch minimum, mild service conditions for applications where the significant surface is shielded from the atmosphere Class B – 0.0002 inch minimum, mild service conditions with exposed significant surface Class C – 0.00032 inch minimum (nonferrous), 0.0004 inch minimum (ferrous),...