According to the website description, all metal surfaces will gradually accumulate the so-called rusty hair, which, when touched, will cause the body to blacken and smoke (apparently rot). Little else is known about it.
This anomaly is a possible reference to the "Cotton" effect in book Roadside Picnic, where all metallic antenna accumulate the thin strands, when touched, the cotton appeared to spread to whatever touched it (The object described in the book was a metal cable, so it is entirely possible it only spread to other metallic items)
Despite not appearing in the game, Rusty hair still exists in the game files, and was set up to create the Thorn, Crystal, and UrchinArtifacts. However, these artifacts are now formed by the Burnt Fuzz anomaly.