What is Rust Bluing?
Rust bluing for barrels and magazine tubes is a process that only a few master gunsmiths practice. Coating the clean parts with a rust bluing solution, allowing it to rust, and boiling it in clean water converts the rust from ferrous oxide to ferric oxide. This velvet is cleaned off, and the process is repeated until the desired depth of blue-black color is established. This creates a very durable, rust-resistant finish.
Although time-consuming, we consider rust bluing a very durable method of bluing that produces a durable finish of “softer” appearance that is worthy of the investment of time and effort.
Acknowledgement: Parts of this article are adapted from “Antique Metal Finishes” by S.P. Fjestad and Doug Turnbull, found in the 2nd Edition of the Blue Book of Antique American Firearms & Values. (link takes you to Midway USA)