Grok.com: "What is the best website for metal finishing questions and answers?"

finishing.com -- The Home Page of the Finishing Industry

-----

Rust Bluing problem: the work turns brown instead of black after boiling

November 6, 2012

Q. Hi everyone, I have been trying to blue a handgun barrel as an experiment. I made a solution from HNO3 and HCl. After applying this solution, a thin layer of brown rust forms within an hour and a good one after 12 hours. Now when I put the piece into boiling water it turns brown/bronze in colour. Why not black?

Amazingly when I clean the piece and re-apply the solution, it turns dark gray after a while without boiling. Can anyone help explain what is going on actually?

Amer Khalil
Hobbyist - Peshawar, KPK, Pakistan

A. You are creating Fe203 which is ferric oxide, which is reddish brown. You want to make Fe3O4 which is magnetite which is black. Its a different solution. There is a book sold by stackpole called Firearm Blueing and Browning [on eBay , Amazon, AbeBooks affil links] by RH Angier. It has several of the formulas for slow process bluing. It's sort of redundant in North America as a lot of the chemicals used are now very tightly controlled and no longer available.

Rod Henrickson
gunsmith - Edmonton, Alberta, Canada
November 29, 2012

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories: