How a Thin Film Protects an Iron Giant
Iron rusts when it reacts with oxygen and moisture. On an ordinary iron surface, that reaction can keep spreading: rust is porous and flaky, so water and oxygen can reach the metal beneath it. A protective film changes the process by forming a barrier at the surface, slowing the conditions that let corrosion advance.
Protection Without Perfect Stillness
The film does not make the iron chemically inert. The surface can still react, but the resulting layer helps shield the underlying metal rather than peeling away and exposing fresh iron. That distinction is why “resists rust” is more accurate than “never rusts”: protection means slowing damage, not stopping every reaction.
For a centuries-old structure, that surface behavior can make the difference between gradual wear and corrosion that steadily consumes the pole. The striking part is that its durability depends not on iron avoiding change, but on a thin layer keeping change near the surface.
