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topic 36214

Formula for cold blackening / cold bluing / cold black oxide



A discussion started in 1995 but continuing through 2020

1995

Q. I am interested in locating any available information on blackening processes for steel, stainless and brass. My preference would be for a cold process. Any help would be greatly appreciated!

D Vanek


affil. link
Birchwood-Casey Gun Bluing

1995

A. Hi, D. You said "my preference", rather than "my requirement", so before talking about the formulation for room-temperature blackening, in fairness to you we should mention that it is generally less satisfactory than hot black oxide (but it is a lot safer). We have a quick FAQ intro to cold blackening on line.

The Metal Finishing Guidebook has a chapter with formulas for solutions for blackening and coloring metals. But better results will usually be obtained with proprietary blackening systems available from the suppliers listed in our directory or in the yellow pages.

For hobbyist level work, cold Gun Blue is readily available in small quantities. Good luck!

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



Digital version
mfg_online

(No longer published, but a copy is on Academia.edu)
Download it before it disappears.

1996

Q. Want cold black coloring process for D2 steel?

Acid resistant, scratch resistant, hard enough . . .

Sayid Budiseno


1996

A. Hello, Sayid.

There are room temperature blackening solutions offered by EPI (Electrochemical Products Inc.) [a finishing.com supporting advertiser], Heatbath and others. We have a brief intro about Hot Black Oxide vs. Cold Blackening on line here, and you'll finder deeper coverage in the Metal Finishing Guidebook -->

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



2001

Q. I want to blacken iron at room temperature. Is there any way to do it? Also, what is the chemical to be used? I would be interested in making my own rather than buying it.

Rajiv Vyas
- Hyderabad, Andhra Pradesh, India


2001

A. Hi, Mr. Yvas. Sorry that I don't know exact formulas, but they're in the MFG. People in the USA rarely make their own metal finishing chemicals anymore, so we tend to not have formulas in memory anymore; the people who know the formulations best are employed by the suppliers and can't reveal them.

However, as a start, I think room temperature blackening solutions are selenium and copper based. Searching patents or searching old journal articles from 20 or 30 years ago with surfacequery.com or scholar.google.com should be productive.

Personally, I find the best room temperature blackening, developed over a period of decades, to not be in the same class as hot black oxides. So I think your chances of developing your own room temperature blackening chemistry that you'll be fully satisfied with are slim. But good luck.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


2003

A. Cold black for iron:
tannic acid .......20 gm
tartaric acid......20 gm
water..............1 lit

Cold black II:
coper sulphate.......100 gm
selenic acid..........45 gm
nitric acid...........50 gm
water.................1 lit

Goran Budija
- Zagreb,Croatia



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



2002

Q. Dear sir,

I want to blacken the mild steel sheets I mean to give them a black colour with copper and selenium based material at room temperature, please guide me in this regard. I want to do it for corrosion prevention as well as to beautify the material.

MUHAMMAD NADEEM
- Islamabad, Pakistan


2002

A. We have an FAQ about Black Oxide and Cold Blackening, Muhammad. The Metal Finishing Guidebook includes a very good treatment of this subject. Missing will be the exact formulations of modern cold blackening solutions, however, as this is the proprietary knowledge of the companies who have invested in the experimentation. Cold blackening offers no corrosion resistance, although the wax or oil you may finish it off with will help a bit. Good luck.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



2005

Q. Dear reader

We are a manufacturer of finishing products in India. Would like get help on :
1. Composition of cold blackening solution of Ferrous metal.
2. Process

Regards,

Suraj Goyal
chemicals - Mumbai, India


2005

A. We have an FAQ about Black Oxide on line here as a quick intro. After that, you could consult the Metal Finishing Guidebook. Then do a lit search and expired patent search. Best of luck with it.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


2005

A. Dear Suraj!
You can use next solution:

6 gms selenic acid
10 gms copper sulphate
4-6 ml nitric acid(1,34 gm/cm3)
1 lit water
20-25 °C temp.
according to Detnner/Elze: Handbuch der Galvanotecnik,1966.

Goran Budija
- Zagreb, Croatia



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



January 6, 2008

Q. Can anyone please assist me with a better formulation and process for "Cold Bluing".
The one I currently have is as follows:

Copper Sulphate 10 %
Selenious Acid 6 %
Nitric Acid 5 %
Demineralised Water 79 %

I am an industrial chemist and am familiar with the hazards of metal finishing chemicals in particular. Regards
Bernie Swart

Bernie Swart
Industrial Chemist & Registered Gunsmith - Western cape, South Africa


January 22, 2008

A. Cold blue:
manganese nitrate...50 gm (up to 75gm)
copper nitrate [affil. link to info/product on Amazon] .....50 gm
Water...............1 lit
50 °C temp.
Hope it helps and good luck!

Goran Budija
- Zagreb, Croatia


January 22, 2008

A. Bernie

The formulation you have is about right for a "cold blue". As you would guess it gives a bluish finish of copper selenide. It is quick, easy, cheap and pretty useless for a working gun.
The durable finish you need comes from a molten caustic / nitrate bath. It is nasty, difficult, potentially dangerous and gives a superb finish.

geoff smith
Geoff Smith
Hampshire, England



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



January 28, 2012

Q. I shall be highly thankful if someone could be given me a guideline for the following: I want to know which compound is used as a surface conditioner / surface activation before Room temperature cold blackening process. It activates the iron surfaces and promotes the formation of uniform, dense and black coating.

Rajkumar Shah
Metal Treatment Chemicals - SURAT, Gujarat State, INDIA



sidebar

Analytical procedure for Selenium Copper blackening solution?

February 22, 2017

Q. I'm looking for analytical procedures to test Se/Cu based darkening solutions. I have some ideas but some guidance would be most welcome. Birchwood Casey offers a 'send us a sample' but they are not specific about what they do. I like to do it myself.

I have an inclination towards ORP measurements; also, total acidity and pH.

Please help.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

----
Ed. note: Blackening of copper is a different topic than cold blackening of steel, but since we're talking about analysis for selenium, the procedures may have enough overlap that this helps the people who are cold blackening steel :-)


February 25, 2017

Q. Hi Sir,

I have the same problem [as Dave] in composition of Se in cold method for darkening copper.

Can anyone help me about detection of selenium?

Asmaa el-sayed
Chemical Engineer - Alexandria, Egypt


March 15, 2017

A. I think the reactions are as follows:

1) SeO2 2- + 6H+ + 2Zn(s) >> Se2- + 3H2O + 2Zn2+

2) 2Cu2+ + Zn(s) >> 2Cu+ + Zn2+

3) 2Cu+ + Se2- >> Cu2Se

Looks balanced to me. This would make the reaction sharply dependent on H+ conc. and the Zn content of the brass.

There is a colorimetric method for Se based on 1, 4 diaminobenzidine, which sounds, and is, carcinogenic. But it's SeO32-, not total Se that's important.

dave wichern
Dave Wichern
Consultant - The Bronx, New York



April 19, 2019

Q. Hi
I want to blue (blacken) hunting shotgun barrels -- Cold or Hot could I be given me any formula for this?

Antonis Tsangari
- LATSIA NICOSIA CYPRUS


April 2019

A. Hi Antonis. Goran offers 3 cold-bluing formulas on the page you are viewing.

TUTORIAL FOR NEWBIES:

People study chemistry in school, and then naturally assume that the way surface finishing is done is by mixing raw commodity chemicals per their school lessons and coming up with their own process solutions. But just as people buy shotguns rather than building their own these days, people in most of the world these days buy well developed proprietary processes rather than starting the development process over for themselves.

In addition to this cold bluing thread, we also have many other threads about blackening -- thread 11740, "Black oxide formula for Hot Blueing of Guns/Firearms" should help you with the hot black oxide formulas. But note that there is more to hot bluing than the formula, and that it is very dangerous due to the risk of this hot solution erupting (water instantly flashing to steam); use hot black oxide only with full protective equipment and in a proper industrial setting. Good luck!

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading



May 27, 2020

Q. Hello, can anyone help me to create a black oxide solution that will do the same as [name deleted for a lot of reasons including the vendor requesting it :-)]
I have a product that I have to mass produce, and the named product is coming out too expensive.

Reading the label it's comprised of selenious acid and phosphoric acids.
Making selenic acid will be tricky, and I would like to know the raw products to use. Apparently you put selenium into nitric acid.

So if anyone can help with this and or the recipe for the solution, that would be a godsend.

Thank you in advance,
John

John Vaughan
- Geelong, vic, Australia


Herters Belgian Blue
brownellsHertersBelgianBlue

[affiliate link by editor to product info at Brownells]

June 2020

A. Hi John. We appended your inquiry to a thread which offers generic formulations for cold blackening solutions. Good luck with them!

Also, there are vendors who sell in quantity, presumably at lower prices if you want to consider that option. We must be cautious about possible legal implications in trying to crowd-source proprietary formulations especially on this "no registration required" website where a competitor or disgruntled employee might try to blow trade secrets, but patents are public info and so easy to access these days :-)

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



September 12, 2020

Q. Hi I found this recipe on this forum and am using to blue steel which will be clear powdercoated for decorative use, could you please help me with the best method to combine these ingredients?

"Copper Sulphate 10%
Selenious Acid 6%
Nitric Acid 5%
Demineralised Water 79%"


Thank you

Shayle

Shayle Casey
- Invercargill Southland


September 2020

A. Hi Shayle. I have no experience with the best sequence for mixing those ingredients, but do have two comments. First, I'm not confident that good adhesion of the clearcoat is assured, because these formulations do tend to be quite smutty. Second, if you're going for blue, you might need highly polished metal; I believe that most blackening treatments tend to look a dark jewel blue color on highly polished metal but more of a matte black on rougher surfaces.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading



September 29, 2020 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hi.I want to get some information about the blackening of carbon steel by cold process.
I am specifying carbon steel and cold process for blackening because I need this process for screwdriver rod which is chrome plated. If I use hot process for blackening then the fumes destroys the look of rod and causes difficulty in further finishing. So, in short....
1. I want to know about complete process for cold blackening.
2. To blacken the tip of rod.
3. The rod is made of carbon steel.
4. And the rod is chrome plated.

Thanking in anticipation.
Regards
A student

Abdullah Bin Faraz
- Lahore Pakistan


September 2020

A. Hi Abdullah. We appended your inquiry to a long thread about how to formulate and monitor home-brew cold bluing / cold blackening solutions.

But I don't think that's the heart of the problem. Rather, I think the question is whether cold blackening will suffice, and I don't think it will. I have seen and used these black-tipped screwdrivers, and although I haven't been involved in their finishing, I very seriously doubt that any high quality ones are cold blackened. I'm not even sure that they are hot black oxided, they might be black nickel or black chrome.

I don't think it would be a big deal to mask the shaft of chrome plated screwdrivers for subsequent processing -- a reusable plastic tube/straw with a centimeter of platers tape top and bottom seems like no big deal, and you have to mask near the tip regardless for a good demarcation line.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading


October 2, 2020

Q. Hi there. Can anybody confirm me that the formula for cold blue/blackening given above by Goran i.e., "manganese nitrate + copper nitrate + water" works or not??
I was going to use formula which is based on selenic or selenious acid but they are not available in my country.
So, kindly help me in using this alternate formula.
Thanking in anticipation
Regards

Abdullah Bin Faraz [returning]
- Lahore Pakistan


October 27, 2020

Q. Hi there again. I have used the formula for blackening given by Goran based on Manganese nitrate and copper nitrate.

Mn(NO3)2 50 gm
Cu(NO3)2 50 gm
Water 1 litre
Temp 50 °C

The whole procedure I have used for blackening is as follows:
1. first I cleaned the metal(carbon steel) with an acid and
dipped it into the water.
2. then I dipped it into the Bluing solution for 5-10 min.
3. lastly I dipped it into oil.

The results are also as follows:
1. it shows the matte black color.
2. the color removes off and makes hand dirtier.
3. sometimes copper becomes visible.

So, kindly tell me how can I:
1. decrease time span.
2. make it look more shiny and deep.
3. prevent it from rubbing off.

Thanks. It worked but not as well as I really wanted. I am facing a problem that is after bluing, copper coloured spots appear on the metal surface, which causes the surface to look badly treated or finished.

So, kindly help me how can I prevent copper from appearing on metal surface.
Thanking in anticipation.

Abdullah Bin Faraz
- Lahore Pakistan

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