被膜

1. Origins, structure, and basic meaning

• Structure: 被膜(ひまく) is a noun for a thin layer covering an object's surface.
• Basic usage: The examples describe the protective role and damaged condition of a film covering metal or a component.

2. Common pitfalls and similar expressions

• Forming a coating and damage in it
  • 表面に薄い被膜を作る describes forming a layer on a surface. In 被膜に細かな傷が入っていた, the film is where the scratches occur, and 入っていた describes the resulting scratched state.