How can soft metals such as lead and tin serve as lubricants?

Soft metals such as lead, tin, and indium function as effective lubricants when applied as thin films over a harder substrate, provided that the adhesion between the metal film and the substrate is strong.1

In industrial applications, these metals facilitate movement by reducing friction between surfaces. For instance, when metal sheets coated with tin are subjected to severe drawing or working processes, the tin coating does not flake off; instead, it acts as a lubricant that benefits the manufacturing process. By serving as a soft, sacrificial layer, these metals prevent direct contact and wear between harder components, allowing for smoother operation under mechanical stress.21