topic 0019
How to Blacken Stainless Steel
A discussion started in 1995 but continuing through 2018
1995Q. Hello, I'm looking for information on the processes available for blackening stainless steel. If you could direct me to any publications or services, I would greatly appreciate it. Thanks,
Terry H [last name deleted for privacy by Editor]UC Santa Barbara, California
adv.
EPI (Electrochemical Products Inc.) [a finishing.com supporting advertiser] blackening processes for stainless
Stainless steel anodizing: B&M Finishers / Prismatic Stainless Steel [a finishing.com supporting advertiser]
Black passivation of stainless steel: Russamer Lab [a finishing.com supporting advertiser]
A. Hi Terry. The Metal Finishing Guidebook lists 3 formulations of blackening baths for stainless steel. The one that sounds simplest to me, although I can't comment on its efficacy, reads:
- Sulfuric acid, 180 parts
- Water, 200 parts
- Potassium dichromate, 50 parts (Potassium Dichromate
[linked by editor to product info at Amazon])
- Operating temperature, 210 °F.
Proprietary processes are also available. Although we don't discuss or suggest particular brands in the forum, the forum is supported by advertisers who offer proprietary blackening products =>
There are also stainless steel anodizing processes and stainless steel black passivation processes. Good luck.
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
1995
A. Terry,
Your question did not specify what purpose the blackened stainless steel is to be used for.
Some of the components inside a TV tube must be "blackened" using a process of heating and cooling in a controlled atmosphere.
Leslie R Williams- England
-----
Ed. note: Please appreciate Leslie's point, folks. People get the fastest and most rewarding answers to their questions if they employ the reporters' creed of "who, what, when, where, & why" when posting their question :-)
2001
Q. Hi,
I am interested in blackening of stainless steel surgical instruments. The finished product is used in laser surgery, aka laser finished instruments. The final product should be a high quality, durable black satin finish.
More information will be greatly appreciated.
Andre Keeve- Atlanta, Georgia
2007
A. For Black color in Stainless steel surgical parts only PVD coatings are recommended such as TiCN or AlTiN ( Titanium carbo nitride or Aluminium Titanium Nitride). There are other colors also possible. These are Thin film coatings and suitable for all surgical and Body implants.
C.LokanathanPVD shop - Hosur, Tamilnadu, India
2001
Q. I am also interested in blackening of Stainless steel. I make etching in knife blades as is covered with Wax. The stainless steel I use is RWL34. The color method must not destroy the wax layer, as it is only the lines as I have drawn in the wax as shall be black.
Lars Tougaard- Faaborg, Denmark
2002
A. Dear Lars,
Consider doing your artwork on a paper stencil and using an electrochemical etch to create the black markings on the steel. The cost of the markers is fairly low and the paper stencils can be made inexpensively. If the wax is a "hard" wax applied thinly, and does not move under pressure, it may work as well as the paper in keeping the chemicals from these areas of the steel.
Try looking for "electrochemical marking" with your favorite Internet search engine to find commercial suppliers for the equipment and chemicals.
The depth of penetration should be between 0.010 mm and 0.100 mm, depending on the chemical and the polarity of the electricity you choose. AC is less, DC is more.
Dave Hass- Oklahoma City, USA
2002
Q. I have started to produce jewelry (Rings) using stainless steel and want to blacken the surface. Any suggestions would be gratefully received. I would prefer a dark, matte finish.
Thanks,
Burt Qwallis- UK
2002
adv.
Burt, please visit our web site - there is a picture of the black finished stainless steel spoons. Quality of the picture is not perfect: the spoon from the right is matte black, the very left one is bright dark blue. In the middle is bright black.
2003
Q. How do you prep stainless steel to accept oxidizers that will color it black in the field for example elevator interiors or doorways and entrances at high-rise office buildings.
#2: What type of chemical will work if not oxidizer?
- Brisbane, California, USA
2004
RFQ: I am looking to have my Smith & Wesson Stainless Steel Revolver blacked. I had the process done to another of my SS revolvers over 12 years ago. Their site mentioned that it produced it's "black coatings on stainless steel and alloy steels by a "conversion" process. The chrome in the stainless steel is involved in a chemical reaction with the oxidizers in the solution producing chrome-sulfide." The finish has held up exceptionally well but that shop no longer offers blackening of Stainless Steel. Please email me with any information.
Thank You,
Adolph AlvarezHobbyist - Vista, California, USA
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2005
Q. I need help blackening or darkening Stainless Steel,
Parts are approx. 20'x 6" x 4"
These pieces need to be welded on site.
Should parts be treated before or after installation?
Will welding affect pre-treated parts?
What Process can be used to do this?
Grateful for any help!
Casting Foundry - Beacon, New York
2005
Q. I am looking for the process which causes the surface of stainless steel to go black. Does it affect the corrosion resistance?
Robert WarkAlstom - Pymble, Sydney, Australia
2005
A. Simple and cheap way to blacken stainless:
Oil it very sparingly (any edible oil),
then heat it slowly to max. 400 °C
Repeat if needed.
Good luck!
Goran Budija- Zagreb, Croatia
September 14, 2011
A. If you heat stainless with an oxy-acetylene torch (neutral flame) until it has an orange glow uniformly, then let it cool naturally it will remain black. Polishing with steel wool and metal polish enhances the finish. This is for cosmetics only. It is a very hard finish but will scratch with sharp objects. It is black about .002" into the metal.
Repeat the process again with a warm water quench and some stainless will harden. The blackening occurs because the chrome and nickel are being burned out. The remaining metal seems to be the same strength, toughness, etc.
- la mesa, California, USA
October 17, 2012 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
Q. Is there a simple way to make chrome steel rods black in color?
Worth Hayden- Winnipeg, Manitoba, Canada
A. Oil it very sparingly, and then heat it to 200 - 400 °C (slowly). Any edible oil or fat can be used, but linseed is the best. You can use hot air gun as source of heat. Hope it helps and good luck!
Goran Budija- zagreb, Croatia
Blade blackening for knife makers
September 3, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative threadQ. I am a small-shop knife maker. Is there a reasonable way to blacken hunting knife blades?
(1) carbon steel ,
(2) stainless steel
… in my shop? It should be effective as a corrosion inhibitor (carbon steel) and should not wear off when used under normal conditions.
Knife Maker - Luray, Virginia USA
September 2014
A. Hi Fran. As you see, we've appended your inquiry onto a thread where Goran answered the question on October 20, 2012 with a method that should be so simple and low cost that you ought to be able to simply try it and get back to us with your comment about it. Thanks. Good luck.
Regards,
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
May 19, 2015
Q. Hi,
I want to know about blackening processes of upper frames of kitchen stoves.
Many thanks for your any help you might give me.
steel development co. - Tehran, Iran
June 2015
A. Hi Shahr. I think what is called in your country "upper frames" might be called "grates" in mine. You are referring to what sits above the gas burner, and upon which the pots and pans sit during cooking? To my knowledge these are usually porcelain enameled. I don't know whether common practice is too dip them in a pot of molten ceramic frit or whether the frit is flame sprayed on them. Hopefully someone else will.
But to my knowledge these are steel or cast iron. I am not aware that they would ever be made of blackened stainless steel.
Regards,
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"
June 30, 2015
Q. We have 50 year old Eldan stainless cutlery which has a floral pattern embossed in the handles with a black tint in the background. The black has faded, especially on the spoons where submersed in the coffee or tea.
How would I restore the tint safely?
- Aurora, Colorado, USA
Q. Hi. We are a signage fabricator. Our client's requirement is for a hotel's room number using black stainless steel hairline finish as a backing for the numbers. I would like to consult other methods we can use to blacken stainless while maintaining the hairline finish of the raw material. Black Oxide patina however is not available from our country. Thank you very much in advance for your replies.
Joan Santiago GonzagaSignAries Advertising - Dinalupihan, Bataan Philippines
September 14, 2017
Q. I am looking to reuse my old s/s kitchen sink in a refreshed kitchen (as I have been unable to source a narrow, full length black sink that will fit within a 470 mm worktop.
I need a durable black or dark grey finish and was originally wondering if it could be somehow coated with liquid plastic (like tool handles). Any suggestions would be appreciated. Thanks.
- London, England UK
September 11, 2018
Q. I am looking for a way to darken a laser engraving on a knife scabbard. Unfortunately, the quality of stainless on the scabbard is nowhere near the quality of the knife. The engraver & my husband explained it is due to different layers of metal. Problem is, it makes the engraving look off, some places it almost appears nonexistent, but you can feel the engraving is there. Is there a way to darken the engraving without damaging the surrounding unengraved, polished stainless steel? The engravings vary in size from 1/4 inch to 1 inch (years of service and emblem).
Kate Lackey- San Antonio, Texas, USA
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