prime coat

例句：

1. 1.The prime coat of the car was scratched by a stone.
   汽车的首层漆被一块石头划伤了。
2. 2.The prime coat of the paint is essential for its durability.
   油漆的首层是其耐久性的关键。
3. 3. The prime coat of the wallpaper is applied to protect it from moisture.
   壁纸的首层是为了保护它免受湿气的影响而涂抹的。