Call me Rusty
For helmets made with metal shells, as well as the silver and brass fittings of leather helmets, rust is a major problem. As these fittings and the helmet shell itself have often not been gilded or silver washed, the raw metal may have been exposed for many years to conditions which encourage the formation of rust.

Rust is a natural process of oxidation on metal and it occurs in two basic stages: active and inactive. Initially, when the surface of many metals (primarily steel) are exposed to air and moisture, rust will begin to form. This is active rust which appears as a reddish brown color and will leave a residue on cloth or fingers when touched.

Active rust eats away at the surface of the metal consistent with the environment that it is in. If left unchecked it will erode the surface of the metal which can be seen as pitting, to a complete encrustation of the surface. The second stage is inactive rust where the surface degradation will cease. Inactive rust in this stage appears as a very dark brown.

To stop active rust, the area must be coated in a petroleum distillate cleaner lubricant preservative (CLP) or a good quality gun oil. For the purposes of preservation, controlling the humidity to inhibit the conditions that rust will form in is critical.