plating       
noun [ U ] uk/ˈpleɪ.tɪŋ/ us/ˈpleɪ.t̬ɪŋ/
 金属(尤指金、银)镀层
a thin layer of metal, especially gold or silver, that is put on top of something
  gold/silver plating 镀金/镀银 
 The gold medals have 6 grams of gold plating over a silver base. 金牌是在银牌的基础上镀了6克金。 
 See: plate
 - More examples
 - The gold plating is now getting a bit thin and tarnished and needs to be replaced.
 - Along with its silver plating, the instrument still bears the name of its maker.
 - The highest quality chrome plating covers all components.