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topic 48674

What is the "Blackodising Process"



A discussion started in 2008 & continuing through 2017

May 2, 2008

Q. We are into auto component manufacturing and want to know about blackodising on steel parts.

Rakesh Darbari
Auto Component Business - Gurgaon, Haryana, India


May 2, 2008

A. Hi, Rakesh. Although I confess that I've never heard the term 'blackodising' used in my country, from numerous letters posted to the site, it is apparent that what American metal finishers call "black oxiding" is often called 'blackodising' by metal finishers in India.

It's an oxidation process (most people have seen it on firearms) and is done by immersing steel in a very hot (290 ° F) solution of strong caustic soda, plus oxidizers like nitrates, that leaves the steel with an extremely thin but attractive black color. It is always oiled or waxed and offers negligible corrosion resistance without the oil, and little protection with it. We have a brief "Black Oxide vs. Cold Blackening FAQ" on line here. You can read a good introduction to the process in the Metal Finishing Guidebook. Good luck.

Regards,

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


July 11, 2011

Q. Dear Sir,
We usually use flash chrome as the finishing process for our base plate (normally of size 800 X 510 X 12). But recently the plating is found not useful due to rusting. Is there any other process which does not involve shining of job. The finish should be matte finish. Do Blackodised jobs rust later on, in absence of oil? because we were planning to try it out.

Vaibhav Khollam
- Pune, Maharashtra, India


July 12, 2011

A. Hi, Vaibhav. Blackodising offers little corrosion protection -- none without oil. The matte vs. shiny appearance of blackodising depends on how matte or polished the substrate was though. A very highly polished surface comes out more dark blue than black.

Dull nickel plating might possibly do for you. But certainly it is possible to apply a corrosion resistant plating sequence that ends with matte black chrome if that's what you want. Good luck.

Regards,

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


August 27, 2011

Q. I AM INTERESTED TO START A SMALL BLACKENING PLANT. PLEASE GIVE AN IDEA.

P.GNANAMANI Mr.MANI
SUPERVISOR IN ENGINEERING COMPANY - HOSUR, TAMIL NADU, INDIA


August 30, 2011

A. Hi, Mr. Mani.

You will definitely want to use proprietary chemicals, whether hot or cold, because you are new to blackening. Please contact any local supplier of plating process chemistry and they will be able to help you choose whether hot or cold is better for you.

adv.
- Hot black oxiding is a major product line for Heatbath [a finishing.com supporting advertiser]
- Cold blackening is a major product line for EPI (Electrochemical Products Inc.) [a finishing.com supporting advertiser]
- Macdermid Inc. [a finishing.com supporting advertiser] is a worldwide supplier of all processes related to metal finishing.

Good luck.

Regards,

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


April 5, 2012 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. What is the difference between Blackodising and blackening process? Please reply.

Ravi gupta
process technology - Ahmedabad, Gujarat, India


April 5, 2012

A. Hi Ravi.

Blackodizing is explained on this page. "Blackening process" doesn't really have any specific meaning, any more than "whitening process" or "brightening process". Blackodizing is one blackening process, but it's easy to imagine others.

Regards,

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


January 15, 2013

Q. Is there any alternative for Black oxidising? Can we go for Zinc plating or other process?

Mahesh Kabra
- Nasik, Maharashtra, India


January 15, 2013

A. Hi Mahesh. Certainly zinc plating can be done... it's the world's most popular plating service. And it can be black if you wish.

But you haven't yet given any indication of what you are black oxiding or why, so people can't guess whether zinc plating will prove okay. Please get back to us with the details of your situation and people can try to help you. Thanks.

Regards,

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


April 26, 2013

Q. Sir I am looking to start my small plant of blackodising. Can you tell me the process of blackodising and chemical required for the process?

Abhijeet Kulkarni
- Aurangabad, Maharashtra, India


April 30, 2013

A. Hi Abhijeet. Please read our FAQ, and then the Metal Finishing Guidebook, and meet with a local distributor of blackodizing chemicals as we've suggested. If that effort leaves you with some highly specific questions, please post them and people will probably be pleased to try to help answer them.

But different steels require different processes and temperatures, and different precleaning, and you need to decide between hot and cold processing, and waxing or oiling, depending on what kind of parts you intend to produce for who and why. And the safety issues of hot black oxiding are very serious. Sorry, but we can't condense the subject of how to specify, design, build and operate a blackodizing plant into a forum response here :-)

After you have read some good introductions, please get back to us with specific questions. Thanks!

Regards,

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


October 28, 2013

Q. Does blackodising a screw help in any manner? Recently we faced a rust issue in the screws and found out that they were blackodised. It's evident that this process does not provide corrosion resistance, apart from our specific requirements, if any, does it help?

Surya Kulkarni
- Indore, MP and India


October 30, 2013

A. Hi Surya. As you say, the corrosion resistance of blackodizing is very little and depends mostly upon periodic application of oils or waxes. The advantages of the finish are its appearance, and the fact that it causes no dimensional change (whereas painting and plating have measurable thickness). It's a finish that is best restricted to items that are lovingly maintained (like firearms), or where dimensional changes aren't acceptable (like bored gears and sprockets), or where there are no corrosion issues (like indoor use in controlled atmospheres).

Regards,

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



Want detailed process and chemistry info for black oxide

May 3, 2014

Q. Dear Sir

I am running my auto component manufacturing industry in India. Many of my components need a blackodising process, and right now we are outsourcing it through a local suppliers. But I think the cost he gives us is not worth it and I think I should start blackodising process in my plant.

I'm a little aware about this process, but I don't know the details. Can you help me out, and please tell me detail process and which chemicals should be used during this process.

Thanks & Regards!

SUMIT AHER
engineering works - Pune , Maharashtra, India


May 2014

A. Hi Sumit. Please begin by reading our FAQ on the subject and then the relevant chapter in the Metal Finishing Guidebook as we've asked twice on this page already. Then you might wish to review letter 1150, "The black oxide process and gun bluing" where Rod Henrickson answers all your questions about chemistry and operating conditions. Then do a search of this site and read additional threads about black oxiding.

But if you do not have access to a knowledgable black oxide consultant, or at least an experienced gunsmith, we must again urge you to go to a proprietary supplier of black oxide chemicals and equipment, as it is quite a stretch to go from even rather good book knowledge to designing, installing, and safely operating a practical black oxiding process. Best of luck.

Regards,

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



Black oxide doesn't work on OHNS steel

August 8, 2014

Q. Dear Sir,

Recently for our customer we are using OHNS material and as per their requirement we are following Induction Hardening. We found that, after Blackodising, the hardened face is giving a reddish appearance. That means the blackodising is not effective for the hardened area. Can you suggest any other process / care to be taken while blackodising? And why this reddish appearance comes to OHNS material?

SATEJ

SATEJ RAJPUT
- Pune, India

ACRONYMS:

OHNS = oil hardened non-shrink steel
or oil hardened nickel steel



December 9, 2014

Q. Why blackodising is needed?

bhushan p patil
student - jalgaon maharashtra india


December 2014

Hi cousin Bhushan. As a student, you may want to practice the synthesis of knowledge acquisition by gathering facts from here and there, and merging the bits & pieces into a fuller picture. Do you understand why objects may require finishing of some sort? Do you understand that every process has advantages and disadvantages compared to other processes? Do you understand that blackodizing is one of those many potential finishes?

If so, then previous statements on this page beginning with "leaves the steel with an extremely thin but attractive black color", "always oiled or waxed", "offers negligible corrosion resistance without the oil, and little protection with it", "matte or shiny appearance", "the safety issues of hot black oxiding are very serious", "It's evident that this process does not provide corrosion resistance", "advantages of the finish are its appearance, and the fact that it causes no dimensional change" should provide plenty of fodder for your essay.

Please prepare and then post a two or three-paragraph abstract and we'll be happy to review it. Good luck.

Regards,

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



Black oxiding, rust proofing, and shipment by sea

March 3, 2015

Q. After Blackodizing for preservation & dispatches of material to overseas which type of rust preventive is required on spring steel material (Disc Spring is the product)?
Is rust preventive oil required after Blackodising process as it is self coating process?
Regards,

VINOD BHINGARDE
- Mumbai,Maharashtra, India


March 2015

A. Hi Vinod. When parts are black oxided, it is not a matter of just dipping them into a single tank, but taking them through a process sequence of cleaning, rinsing, activating, rinsing, oxiding, rinsing, boil-out and post-treatment with wax or oil. So, when you ask whether black oxiding involves a dip in rust preventative oil, or whether it's a separate process, it's a question of semantics, i.e., whether you are referring to the black oxide tank proper or the usual black oxiding sequence.

In any case, even with a dip in good rust-preventative oil, the corrosion resistance will only last as long as the oil. If shipping overseas, you must keep the environment away from the parts. The parts must be literally drowning in oil that keeps the salt air away, or they must be sealed away from it.

Regards,

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



Root cause for black oxided parts failing 24-hour salt spray

July 30, 2015

Q. Dear sir,
please tell me: we are using blackodising process on parts, but they are getting corroded, so please suggest what is the root cause? I have checked parts in salt spray test; they get corroded in 24 hours. So please reply to us.

yogesh singh yadav
- nashik, maharashtra, India


September 2015

A. Hi Yogesh. The root cause is that your process does not produce parts with sufficient corrosion resistance to resist salt spray for 24 hours :-)
What are the parts made of, and what is the process sequence (including the lacquer, wax, or oil) that you are employing? Please don't expect black oxided parts to resist 24 hours of salt spray without an effective lacquer, wax, or oil post-treatment! You're lucky when they can resist the ambient environment for a 1/2 hour without flash rusting :-)

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



December 5, 2015

Q. Why is there a shade difference between Castings and MS parts after Black Oxidizing?

Manoj Kajale
- Pune, Maharashtra, India


December 2015

A. Hi Manoj. Castings and MS are entirely different metals (for example, lots of silicon in castings), so it's to be expected that they won't automatically adopt the identical look when oxidized. I don't know enough about black oxiding to answer your question well ... because what you probably would really like to know is what to do to get them to look more like each other. But I think the first step is an equal degree of polishing. Hopefully an experienced black oxidizer will jump in and help :-)

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



sidebar March 23, 2016

Q. Is it possible to blackodize on aluminum? If possible please provide the details about chemical and process.

Harsh panchal
- Kadi, Gujarat, India


March 2016

A. Hi Harsh. As I said earlier in this thread, I have never heard the term 'blackodize' used in the USA, but it is apparent that it is widely used in India to describe the same process which we in the USA call 'black oxiding' or 'bluing' of steel (and sometimes cast iron and stainless steel). It is a process that works on ferrous metals not on aluminum.

There are a number of ways to get a black surface on aluminum: anodizing and black dyeing; zinc plating and black chromate; plating with black nickel or black chrome, painting, powder coating, etc.

If you can tell us what you are trying to do, i.e., what properties you are trying to give to the aluminum, in what environment, and for what reason, I think we can assist you -- but you can't say you want to 'blackodize aluminum' because, as far as I know, that wouldn't have any meaning at all. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


March 28, 2016

A. Dear Harsh,
I think you want black colour on Aluminium. It can easily be achieved with help of dye colours or electro colour after anodizing.

Happy Anodizing.
Regards

Sumit Lodha
- ahmednagar Maharashtra India



Possible to black oxide a nitrided surface?

April 19, 2016

Q. I want to cover patches on the ground (grinded) surface of a part which is already gas nitrided to increase its hardness. Can blackodising affect the nitriding results?

sachin raut
sunfab automation - Pune, Maharashtra, India


April 2016

A. Hi Sachin. If I understand your situation, you gas nitrided some parts but you are unhappy with their patchy appearance in the ground area so you want to black oxide them. Although I have no personal experience with it, my understanding is that this can work, i.e., that you can blackodize nitrided metal without harming it ...

However, the black oxide is millionths of an inch thick, and not hard, and will quickly wear off. You might consider the QPQ salt bath nitriding process instead. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



Removing/stripping black oxide finish

June 29, 2017

Q. I have a cutter made up of HSS and EN19 material which is blackodized. But company requirement is without blackodizing.
So what can I do to removing blackodizing? Suggest please.

sandesh londhe
tools - pune, maharashtra, India

----
Ed. note: Readers may wish to see letter 3974, "Removing Black Oxide Coatings".



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