back scrubbing

例句：

1. 1.The machine needs to be cleaned regularly to maintain its efficiency.
   机器需要定期清洗以保持其效率。
2. 2. The car was given a thorough back scrubbing before the new paint job.
   汽车在新的油漆工作之前进行了彻底的回刷。
3. 3. The engineer decided to do a back scrubbing on the old engine to see if it could be repaired.
   工程师决定对旧引擎进行回刷，看看是否可以修复。