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Black oxide formula for Hot Blueing of Guns/Firearms

Adv.   


Q. I want to know the exact composition of the bluing salt used for the bluing of M.S. Also the chemical composition of chemical Degreaser (Alkaline). Also could you guide that some parts developed white powder at many areas after one day of bluing. Could you propose remedy for it?

Thank you,

Tayyab S deleted
- Islamabad, Pakistan


May 26, 2008

A. Hi, Tayyab. Black oxide solutions are essentially composed of sodium hydroxide, sodium nitrite, and sodium nitrate. Alkaline cleaners are largely sodium hydroxide, but also usually contain sodium silicates, sodium carbonates, sodium tetraborate, TSP, other sodium phosphates, soaps, and surfactants.

Most plating shops in the West buy proprietary alkaline degreaser processes and black oxide (bluing) processes from specialty suppliers, and the exact compositions of the proprietaries are held as trade secrets which people can't share.

We have an FAQ on Black Oxide and Cold Blackening to introduce the general technology. Beyond that, the Metal Finishing Guidebook goes into more depth about the general technology.

Regarding the white powder, please see letter 13097 "Black Oxide Problem". Good luck.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



+++++

Q. What is the correct formula of hot caustic bluing for making up a bluing bath for refinishing guns, and can we regenerate the bath again and again , and how can we extend the life of the bath, as I am making the bath in the following manner:
caustic soda 10 kg
sodium nitrate 10 kg
water 10 liters.
The bath forms red cast on the parts which is easily rubbed off but the bath lasts only an hour or so -- please advise.

Inderjit Sidhu
firearms - Patiala, Punjab, India


+++++

A. Hi Inderjeet,

Forget about your formula search and buy the correct ready-made product from any reputed company in your country.

khozema Khozema Vahanwala
Saify Ind
 
Bangalore, Karnataka, India


 appended

Q. Hi, I am on the look out for bluing chemicals, details of chemical composition, process, suppliers and pricing details on polished steel parts. The process is hot bluing, on heat treated components.

Regards,

Rishabh Kapoor
- Delhi, India


++++++

Q. What is the formula for gun bluing hot caustic blueing for home-made. I want to blue my gun. It is old and has rust.
Thanks.

Santi Salinas
- Quito, Ecuador


+++++++appended

Q. Does anybody know the formula for the black oxide process? Concentration, chemicals used, procedure? Thanks.

Daniel Hernandez
plating shop owner - Bucaramanga, Colombia


+++++++

A. Black oxide formula: 600 gm sodium hydroxide, 25 gm sodium nitrite, boiling solution, immersion 10-30 min, rinse well; it must be oiled, waxed or lacquered.

Use rubber protective glovesamazoninfo, protective clothing and safety gogglesamazoninfo !
Hope it helps and good luck!

600 gm NaOH, 25 gm nitrite and 1 lit water!

Goran Budija
- Zagreb, Croatia


+++++++

thumbsup2Thanks,
It works. Thank you very much

Daniel Hernandez [returning]
plating shop owner - Bucaramanga, Colombia



Why don't gun shops know hot gun bluing?


Q. Dear sirs:

I have been to many "gun" sites and could not find a formula for "hot" gun blueing. I have found your recipe to be very interesting. Why couldn't I find it elsewhere?

Eric Pdeleted
- Philadelphia, Pennsylvania



A. Hi, Eric. I'm not sure, but possibly two reasons: first, many of our readers are professionals so they frequently reference and quote the metal finishing textbooks whereas your average gun enthusiast probably wouldn't; second, hot bluing is a dangerous operation that should probably only be practiced in a proper industrial setting, not in a back room of a retail store. Best of luck.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

A. Eric,

You can try "gunsmith supplies" search and probably find instructions and bluing compounds. The modern bluing solutions are very good and it probably wouldn't be worth trying to make your own. As was said, hot bluing is not a back room project. The solution I use is a caustic soda solution heated to 300 °F. It will eat thru leather, wool, skin, etc., and will cause chemical and heat burns. The fumes will deteriorate any metal in the area, so a very good ventilation system is required. Personal protection is a high priority.

Good luck,

Ed Kay
- St. Louis, Missouri


June 5, 2008

A. Hi Eric,

I have an old engineering book "Dictionary of Metals and Alloys" 1939, which describes the HOT BLUEING process very well and safely and I have used it with good success.

Thoroughly clean the articles in ammonium sulphide, and hydrochloric acid for a "few" minutes" will lightly etch the surface and create a light rusted effect which will improve the depth and darkness of the finished result.

Coslettising bath of a heaped desert spoon of phosphate of iron to a liter of water which needs a few drops of phosphoric acid to dissolve into solution ... boil the articles for 1/2 an hour or more ... longer produces deeper penetration to a small extent ... leave to dry overnight and oil.

Granodising is an electrolytic process using a solution of zinc phosphate acidified with phosphoric acid and passing a light current from the negative cathode (the article) to a carbon anode. Articles acquire a dense black coating which is highly resistant to oxidising ... can be applied to zinc, cadmium, iron steel, stainless steels and copper/brasses etc

Errol Churton
Carver - New Zealand


Why is bluing too dull to match rest of gun?

+++++++

Q. Hello, I have a pre war model-70 Winchester. I just had the floor plate, trigger guard & screws blued. however they are too dull to match the rest of the gun. Can these parts be polished by me to bring out more luster to match the rest of the gun? thanks,

Bruce M Hissom
retired - Star Junction, Pennsylvania


+++++++

A. Hi Bruce. The coating is too thin to polish. The bluing can be waxed or oiled to bring out a bit more luster, but I suspect what really needs to be done is to polish the bare metal and re-blue it. The same black oxiding compound that generates a jewel blue on a highly polished part produces a matte black on a rough part :-)

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


Inconsistent results: Bluing doesn't work on all parts

December 11, 2009

Q. I have tried my hand at Hot Caustic Blueing. I have a couple of problems I need assistance with. I have several parts that did not blue. Several that did. One that looks like it has freckles on parts of it. I thought all parts were the same type of steel. They all draw to a magnet. My frame did not blue at all. My slide blued to a good color but has freckles at edges. They were in caustic bath at same time. Some of my small parts also blued and some didn't. They to were also in caustic bath at same time. Any Ideas? Thanks Skip

Skip Kalmar
Hobbyist, maybe One day gun smith - Heath Ohio


December 2, 2010

A. Hi Skip,

Since it didn't look like you ever received a response, I thought I'd throw in my 2 cents.

Stainless used in guns is 400 series and magnetic. It will not blue in ordinary salts. There are salts available for stainless. Some alloys work and some don't.

It's always advisable to try to blue a matte finish vs. a polished finish. Polishing stainless is almost always a guaranteed failure.

Speckles on edges are indicative of poor cleaning. When the part goes into the solution, if there is any floating oil, the part will pick them up and it acts like a mask and the salts won't penetrate it.

Hardened parts, castings, will leave a red to purple tint and again, the courser the finish, such as matte, will offer a greater chance of a darker blue.

Hope this helps!

Mark Smith
precision bluing - Greene, New York, USA


April 20, 2014

Q. Please give me a proper hot procedure. I am using ms tank.

gosai jaydip
heat engineering works - Surat, Gujarat, India


April 2014

A. Hi Gosai. Many plating texts will offer this general information. For example, The Metal Finishing Guidebook suggests:

8 lb. caustic soda,
1-1/2 oz. sodium nitrite, and
1-1/2 oz sodium dichromate
... to 1 gal. of water, operated at a boiling point of about 295 °F. Goran has offered a rather similar formulation.

But personally, I believe Khozema and others have offered the best advice, i.e., to go to a reputable supplier of blackening salts who will supply proper salts with quality control, a technical data sheet on how to use them, a technical service person who will know what they are looking at and how to troubleshoot any issues, and an experienced lab when trouble develops. When professionals with decades of experience in this recognize that they are better off buying the product than trying to formulate it themselves, people with less experience should probably heed their advice :-)

As you read these pages you'll find that potential troubles abound, and if you don't know from long experience whether the problem is formulation, operation, defects in the substrates, improper cleaning, wrong expectations, or whatever, it can be extremely difficult to function efficiently. Using proprietary solutions can cut that problem down to size. Best of luck.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


June 1, 2014

Q. We are doing Hot Black Oxidising on High Tensile Fasteners. We use Caustic, Sodium Nitrate and Sodium Nitrite in the ratio of 80:10:10. Can anybody guide what are the characteristics or the function of each chemical in this?

Regards
Chintan

Chintan Mehta
- Bhavnagar, Gujarat, India



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