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How to Blacken Stainless Steel
Quickstart:
A principle advantage of stainless steel over other metals is that its corrosion resistance runs through & through rather than requiring a coating that can wear through over time. Thus, because blackening or otherwise coating stainless steel tends to neutralize its biggest advantage, it's less common than most finishes.
The black oxide process causes black rather than red rust to form; the black form of rust is more stable and somewhat corrosion resistant. It's widely done on plain steel but less commonly on stainless. Stainless steel resists rusting, whether red or black, so it is more difficult to blacken stainless, and proprietary chemistry is often used.
Other ways to blacken stainless steel include painting, powder coating, black nickel plating, black chrome plating, zinc plating followed by black chromating, electro chemical etching, physical vapor deposition coatings or, for small premium parts like jewelry and watch dials, ruthenium or black rhodium plating.
Q. Hey there, I work for an aftermarket auto parts company that produces high quality roof racks and other exterior products. All of our products receive a black exterior grade powder coat finish, and thus we use black finish fasteners. We want to know what the best finish option would be for a black stainless steel fastener that is resistant to UV exposure, salt, road debris, etc.
Brian HilleProduct Manager - Scappoose, Oregon
May 16, 2023
A. Hi Brian. If you mean really high quality, then black chrome plating is probably the ideal. A black PVD finish may be excellent too.
More affordable but still probably very good would be zinc-iron plating with black chromate. Depending on the type of fastener and the tools required for it, electro-painting or selective powder coating might be okay, but tools can obviously chip organic coatings.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hey Ted,
Thanks for your previous response. It was quite helpful, but we ran into issues finding suppliers that were able to provide the Black Chrome finish to our fasteners due to apparent governmental regulations.
We typically spec 18-8 SS, 304L, and in some cases 316L for our fasteners. Everything we spec is an "off the shelf" item in the US, if that makes a difference. We have no issues finding the correct hardware in SS, but we have continually struggled with an appropriate black finish. E-Coating was an option we had went with for awhile, but have since abandoned due to inconsistencies in finish thickness, and the fact that the finish chips and flakes so easily. Powder coat is simply not an option due to the machine tolerance required, as well as the cost and volume of hardware we purchase annually.
Our current path has led us to a "Low Temp Black Oxide" but we have concerns about that due to potential for corrosion when applied incorrectly or contaminated as I've read in other threads here on your site.
I'm hoping for your thoughts on the aforementioned, as well as further explanation on your previous suggestion of PVD (what is this?)
- Scappoose, Oregon
A. Hi Brian. Yes, Oregon and the Pacific Northwest often have tough regional and local environmental restrictions including, I've heard, de facto bans on chrome plating in some areas.
Stainless steel hardware is still stainless steel so, unless processed badly, I don't think black oxiding will hurt its corrosion resistance. Part of the answer there is probably to have your plating shops use high quality proven proprietary products rather than mixing up home-brews. We can't post suggestions of brands or sources on this "no registration" site ( huh? why?) but please consider as paid advertisements our supporting advertisers Birchwood Technologies [a finishing.com supporting advertiser] and EPI / Electrochemical Products Inc. [a finishing.com supporting advertiser], well-known as specialist suppliers of black oxiding processes. You might contact them for their suggestions.
As for PVD, it stands for 'physical vapor deposition'. It is done in a vacuum chamber with the coating applied in gaseous or plasma form rather than liquid form, so it pleases the regulatory authorities. It is only applicable to reasonably high volumes because shops will not risk contaminating their million-dollar-and-up vacuum chambers doing onesy-twosy jobs, but hardware is a high volume application. The coatings tend to be nitrides, carbides, or other very hard and wear-resistant metallic compounds. The familiar gold-colored drills are PVD coated with titanium nitride; I believe there are suitable black, or at least blackish PVD coatings. Please see C.Lokanathan's posting below, or thread 35541, "How to achieve a Black PVD finish" for more info on that possibility.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hello,
I am new to the forum and I have a question regarding the preparation of a stainless steel piece before performing a black oxide reaction.
Indeed, it seems that the preparation of the piece before the black oxide reaction is extremely important for the blackening to work.
Therefore I was wondering if anyone could provide with the detailed steps to perform (degreasing, acid cleaning...) for the stainless steel to be perfectly clean before performing the black oxide reaction.
Also, if anyone had tips regarding which is the most reliable solution to use to perform black oxide on stainless steel, that would be very much appreciated!
Thank you very much for your help!
Best regards,
- Levis, France
February 4, 2025
Tip: This forum was established to build camaraderie among enthusiasts through sharing tips, opinions, pics & personality.
The curator & some readers who publicly share their info will be less likely to engage with those who don't.
A. Hi Francois. It's true that metals must be properly prepared before metal finishing processes. Abrasive blasting followed by hot alkaline cleaning (preferably a proprietary cleaner) and dilute HCl acid dip should constitute good pretreatment. If abrasive blast isn't practical, you'll probably need a stronger acid ... some say 50% HCl.
I don't think that's the only problem in black oxiding stainless steel though. Stainless steel isn't the same as low carbon steel, and isn't going to blacken like low carbon steel just because you've presented a clean & active surface. It requires chromates or proprietary solutions for reliable blackening. The major metal finishing process suppliers know how to do this and will help you if you use their proprietaries.
adv.
EPI / Electrochemical Products Inc. [a finishing.com supporting advertiser]
Birchwood Technologies [a finishing.com supporting advertiser]
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
⇩ Related postings, oldest first ⇩
⇦ Tip: Readers want to learn from your situation;
so some readers skip abstract questions.
Q. 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
1995
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 ⇦ on
eBay or
Amazon [affil links]
, 50 parts
- Operating temperature, 210 °F.
Proprietary processes are also available. Although we don't discuss/suggest particular brands in the forum ( huh? why?), the forum is supported by advertisers who offer proprietary black oxiding products for stainless steel.
There are also PVD processes, painting & powder coating, stainless steel anodizing processes and black passivation processes. There are all sorts of black electroplating and electroless plating processes.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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.
- England
Ed. note: Please appreciate Leslie's point, folks. People get rewarding answers if their questions follow the reporter's creed of "who, what, when, where, & why". Ruthenium plating, for example, might be a great solution for the dial of a luxury watch, and powder coating might be perfect for a pedestrian railing but each is a preposterous suggestion for the other application, so it's difficult for a reader to help you if you haven't detailed the situation 🙂
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.
- Atlanta, Georgia
2001
A. For Black color in Stainless steel surgical parts only, PVD coatings are recommended such as TiCN (titanium carbo nitride) or AlTiN (aluminium titanium nitride). These are Thin film coatings and suitable for all surgical and body implants.
C.LokanathanPVD shop - Hosur, Tamilnadu, India
2007
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
2001
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.
- 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,
- UK
2002
adv.
Burt, please visit our web site - there is a picture of black finished stainless steel spoons.
Anna Berkovich
Russamer Lab
Pittsburgh, Pennsylvania
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
2003
Q. 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 its "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.
Thank You,
Hobbyist - Vista, California, USA
2004
Q. I have a Vintage Black Titanium Watch whose band broke years ago. Since then, I cannot find another Black Titanium Band to match. Would I be able to take a stainless steel band and "Match" it to the watch itself via Plating it or coating it?
If I cannot match it, would I be able to Plate or Coat the entire Watch Housing and band in a flat black color.... that will not wear off when worn?
Thanks in advance for the Help!
- Boca Raton, Florida
2005
Hi, Jay. It doesn't sound practical to me. Lots of black titanium watches have black leather bands. Maybe yours could? :-)
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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!
- Cerovski vrh Croatia
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 00 steel wool
⇦ on
eBay or
Amazon [affil links] 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
September 14, 2011
Q. Is there a simple way to make chrome steel rods black in color?
Worth Hayden- Winnipeg, Manitoba, Canada
October 17, 2012
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- Cerovski vrh Croatia
Blade blackening for knife makers
Q. 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 3, 2014
A. Hi Fran. As you see, we've appended your inquiry onto a thread where Goran answered a similar question with a method that should be simple and low cost enough that you can try it and get back to us with your comments about it.
But corrosion-proofing carbon steel is not very simple, and most reasonably priced blackening methods are quite thin and nor particularly durable. PVD processes or black chrome plating would probably fully satisfy your needs, but at significant cost. Thanks. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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Q. Hi, steel development co. - Tehran, Iran May 19, 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 to dip them in a pot or fluidized bed 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 be made of blackened stainless steel. Regards, Ted Mooney, P.E. RET Striving to live Aloha finishing.com - Pine Beach, New Jersey |
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
June 30, 2015
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
August 13, 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 14, 2017
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 non-engraved, 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
September 11, 2018
Readers: We have a dozen informative threads about blackening stainless steel. Please search the site with "Black stainless" plus other specific search terms if you didn't find your answer on this page.
adv.
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