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topic 13935 p2

Black Oxide for Stainless Steel 17-4



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A discussion started in 2001 but continuing through 2020

December 5, 2008

Q. Dear Sir,

A tooling instrument using material 17-4, the process as follow:

1. Operation processes
2. Heat treatment to 40-45 Hrc
3. Bead blast
4. Black oxide coating

I am facing the problem of black oxide & blacken for stainless steel 17-4, that unable to cover the material surface cause wear off easily.

What about "special blacken", does it work?

What is the solution to do it like "blacken" the stainless steel 17-4?

I look forward to your reply soon. Thanks.

Regards,

Kent Ong
industrial user of metal finishing services - Malaysia


December 9, 2008

A. Dear Kent Ong,
I have few more questions in turn, to put forward here that would benefit the discussion.

1. Which method you do follow for blackening (Cold / HOT)stainless steel. (There are contradict view on possibilities for stainless blackening at room temperature)
2. What is the process (operating) temperature at which you carry out the Blackening process.

3. What is the least thickness of black oxide coat you tend to achieve, despite oxide scale thickness resulting from blackening process is not measurable in general.

4. How do you qualify the blackening process?
(If its Corrosion test, exposure time?).

Literature/Practical understandings:
1. Cold method can't be used for stainless steel.
2. 17-4 is a precipitation hardened stainless steel. Can there be direct correlation of aging temperature and blackening process temperature in altering material hardness / strength / corrosion resistance that results in wear.

KASI SUBBIAH PERICHIYAPPAN
- Bangalore, Karnataka, India


November 17, 2010

Q. Hi, KASI SUBBIAH PERICHIYAPPAN

The Black oxide or Blackening done by supplier. I may lack of knowledge to answer that supplier did not exposure how the process do. Anyway you are giving the understanding.

To answer your questions as follow

1. As I know is HOT method for blackening.
2. Boiling temperature about 100 °C plus
3. Not thickness control, as long the part appearance is dark or black enough to meet.
4. There is no corrosion test on the part, but 17-4 is stainless steel would said cannot be corrosion so easily.

Regards
Ong

Kent Ong [returning]
- Malaysia



Jewelry designer needs Black Oxide for stainless steel: dry finish safe for continuous contact with skin

March 26, 2009

Q. Hello! My name is Nikki Taylor; I am an independent jewelry designer currently working with laser cut metals (mostly stainless steel, brush finished, 12 gauge). I am trying to find a solution that I can use to achieve a black finish on stainless steel for bold contrast against paler skin tones. I have contacted several companies that sell a room-temperature solution to oxidize the steel (like Insta-Blak). Upon further inquiries into these products I was told that the finish may "rub off" (I'm not sure if this implied immediately like wet paint, or over time and naturally) and that the dried finish would be harmful to have against your skin.

What I am looking for is a way to turn stainless steel (I also have the ability to cut mild steel) black and have it be safe for continuous wear against skin. Also, I am not extremely opposed to slight wearing of the finish over time where it touches skin, but I am hoping to find something that will last a long time without the use of lacquer. I need to be able to finish around 800 small pieces per month so a dip finish is preferred over something brushed on.

Finally, if it is determined that I cannot do this myself in my studio, I'd love to know who I can contact to inquire about finishing the pieces for me. I am located in Kingsport, Tennessee, USA but happy to ship my items anywhere in the Country for this service.

Thank you for any help you can provide! I appreciate your time spent reading my inquiry!

Nikki Taylor
jewelry designer - Kingsport, Tennessee, USA


March 31, 2009

A. Hi, Nikki. You are correct that room temperature blackening will rub off; it's a smutty finish; but it's also likely you aren't properly activating the stainless steel. Black rhodium plating or ruthenium plating are more complicated and expensive, but good possibilities for jewelry. Good luck.

Regards,

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 :-)



April 22, 2010

Q. I have a part that is Stainless Steel 316. It has been blackened per MIL-DTL-13924 [link is to free spec at Defense Logistics Agency / dla.mil] Class 4 and sat on a shelf for two years. What should my part look like after this time? Should the finish be able to be rubbed off by my thumb? These parts were oiled after finishing, but the oil has since dried. Will this leave a residue on my part?

Brian Baker
Engineer - Grand Rapids, Michigan


April 24, 2010

A. Well the link you provided takes me to a Ho sheet which is a "buy me and I'll tell you what site". I have no desire to buy anything but I have seen enough MIL spec sheets to know that it will simply be a list of what the object should survive and what it should be coated with and what general color it should be. It won't tell me what system and what chemicals were used to create the black oxide coating and that information is what is need to back track the procedure to figure out what went wrong. It's like saying my bird should have yellow feathers but all the feathers fell off my bird. Yeah, the feathers are gone and it looks like hell but I have no idea what you exposed it to. A sheet of paper that says the bird is supposed to have feathers does not quite cut it.

A list of chemicals and procedures used is necessary. And no, the blueing should not come off if the parts are oiled with a non-detergent oil and are sitting quietly, dry, unexposed to chemicals and unhandled by human hands. Also you will find that after two years of sitting many oils will polymerize and leave an unsightly plastic like coating on the object. There are some long term storage treatments like the old military cosmoline that will not harden or dry out but most machine shops are unaware of them and do not use them.

rod henrickson
Rod Henrickson
    gunsmith
Edmonton, Alberta, Canada



thumbs up sign Hi Rod. Thanks.

I, not Brian, added the link to the Mil Spec that he mentioned. Although there is no such thing as truly free, anyone can get this spec free at quicksearch.dla.mil. The "not really free" part is just that American shops are taxed so their offshore competitors can get this free leg up on them.

But I understand your point that the Mil Spec doesn't actually tell us how to blacken the stainless steel, nor the details of what Brian's shop did that might explain why the black oxide is rubbing off :-)

Regards,

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



June 13, 2013 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. For about the past month the product we put through our black oxide tanks, the black rubs off but it's just the surface film. Dry touch or regular oil, it still does it. Any ideas?

Mike Find
- Buffalo, New York, US


A. Hi Mike. Please read the earlier entries on this thread to get a feel for some possibilities, then get back to us with clarifying details. Thanks.

Regards,

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



Black process leaves color on hands

October 19, 2015

Q. We are manufacturer of fasteners. I am working at plating shop and facing problem regarding black oxidizing process on nuts bolts. Solution contents are:
Tank volume 400 ltr
Sodium hydroxide (caustic Soda) 75%
Sodium nitrate 25%
Solution temperature 110°C

Process we are doing:
Acid pickling for 20 min
Water rinsing
Process for 10 min
Hot water (not boiling) rinsing
Coating of rust protective oil
In our process the material leaves black color on hands. After cleaning with cloth the material's color comes perfectly OK.

Please guide me why the color leaves in unloading?

arshad masood
plating shop employee - karachi, sindh, pakistan


A. Hi cousin Arhad. Thanks for the details. In the USA most shops use proprietary formulas from suppliers like EPI (Electrochemical Products Inc.) [a finishing.com supporting advertiser] rather than the handbook formulas for blackening stainless steel. So, sorry, I don't personally know how to improve your formula to make it work better on stainless steel. Maybe another reader will, and Steve seems to be suggesting that good activation of the stainless is necessary :-)

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 :-)



Hot Black oxide on Stainless Steel is rubbing off

August 23, 2017

Q. Hello, my name is Dan. I am a shop/Fabrication manger for a company that makes mounting hardware for glass. I have been doing Cold Black oxide in my shop for a few years now and I can get a satisfactory product NOW (a lot of time and work put in). That being said, it is very time consuming and labor intensive. So I decided to outsource to a company that does HOT Oxide as my company is expanding.

They were able to give me a sample and it came out great. I have now sent them a larger order and they are having issues with the oxide taking to the pieces. Now I know the first question is going to be about the processes they are using and I have seen them and am confident they are doing it correctly with the process; I can't comment on the the times, temps, or formula they are using but they have been open and oxidizing for 40 years ... I think they should know by now. My question is that I have done as much research as I can and have found a few possible problems but none have been the issue yet. They (my plater) tell me that the Stainless steel must be contaminated but I have the results from when it was made and tested was all fine. They are Dipping 4 pieces that assemble into one hardware at the same time in the same tank and 1 of 4 are coming out flawlessly the other 3 just rub off the black when touched. I'm hoping someone has some insight on my problem. I am willing to answer any questions to clarify; just hoping I have provided enough info. Thanks. Hope to hear from someone soon.

Parts are,
304 stainless all parts
High speed machined
using proper cutting oils (water soluble)
approx. round 1 1/2" (dia) x varying lengths all under 3"
Through holes on 2
Blind holes on 1
Screw is the part that is coming out great
Some holes are threaded

Dan B [last name deleted for privacy by Editor]
Product Designer - Etobicoke ON, CANADA


August 24, 2017

A. Hi Dan,

You are correct that the first question will be about the process. Black oxide over stainless is an art that typically requires some effort in tweaking parameters when starting a new job. I'm guessing that the coating is very smutty and leaves the part only matte gray when wiped off? If that's the case, what are they using to pickle, what's the concentration, and what's the immersion time? I would look into cutting the immersion time a bit as a first step, and even play around with cutting back your process time in the black oxide bath. When it comes to blackening stainless, usually less is more.

Jameson Grout
- Springfield, Massachusetts USA


September 5, 2017

A. Dan,

Jameson is correct, excessive time in the black can cause the finish to rub off. We no longer perform this process (mainly due to all the similar issues we faced as a job shop), but one other possibility comes to mind. Since you have already stated that all of these parts are made from the same material, is your plater using different types of tooling for these various parts (hooks, baskets, wire, etc)? Dissimilar metals or a mix of metals can sometimes cause adverse reactions in these baths.

Bruce Brady
- Lincoln, Nebraska USA



October 12, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Dear all,
I deal with hot bluing process, so after blasting specially in case of rework, I carried out the bluing process, it gets blued good finishing but color removes didn't stop, as much you apply the oil and just keep on cleaning, color still removes, so how can I avoid this.

Thanks & Regards,
Aijazullah

Aijazullah Tajir
- Abu dhabi UAE


November 3, 2017

A. Aijazullah,
When hot blackening steel there are three common causes of rub off: boiling temperature is too high, slow transfer time between black oxide bath and the rinse, and high colloidal iron built up. As I mentioned in a previous post, blackening stainless exhibits smutty rub off more often but this is usually related to pre-treatment or process time.
The topcoat oil has no effect on this and you can't clean it off.
In my experience rework parts don't exhibit rub off more often than virgin parts. Are you adequately removing the topcoat oil before blasting off the oxide? Its a stretch but if you're embedding oils during your stripping process that could interfere with the black activation. I've seen cases where a lubricant your degreaser can't remove can lead to rub off.

Jameson Grout
- Indian Orchard, Massachusetts



Cold blackening a Scotty Cameron stainless steel putter

July 14, 2018

Q. My situation:

I want to color a 303 stainless Scotty Cameron putter.
I've got the putter all dialed in and have sandblasted it
I then used stainless steel blackener from a hobby plating supplier after I put it in muriatic acid.
It came out all blotchy and just awful.

Could someone point me in the right direction.

Thanks,
Justin

Justin Davies
- Calgary, Alberta


July 2018

A. Hi Justin. You are welcome to try anything you want and I'm not here to discourage you! But sorry, I don't know you and your skill level, so this isn't personal, but a basic problem may be the assumption that you can get a Scotty Cameron class finish on stainless steel from amateur cold blackening. You can't.

If you have the time to read them, you'll see that we have many threads on black finishes for stainless steel. Black finishes may be done with PVD processes, including diamond-like carbon, maybe specialty proprietary anodizing, or black chrome plating, many other black plated finishes or … maybe hot black oxide if done by professionals with experience and top quality carefully monitored and analyzed proprietary solutions (although even that is apparently questionable). But my guess is that cold blackening of stainless steel will never give you the quality you seek for a putter which costs hundreds of dollars. Sorry to bear bad news but cold blackening is a fairly low quality finish no matter how well done.

Regards,

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



Black oxide on stainless steel surface is not even

March 27, 2020

Q. Dear All,

We are doing black oxide on a very small stainless steel part (SUS 304). 0.1mm thickness with width about 3mm x 3mm.
The main purpose of doing it is to cover the part with black matte colour.

However, the result is not good. The black colour is not evenly spread on the surface. We are having overlapping issue when doing this also.

We also tried to do heat treatment first and then go for black oxide. It is better but still the colour of surface is not evenly spread.

Please help.

JJ TAN
- Malaysia



May 24, 2019

Q. I'm having some parts black oxide coated. The same place has been doing them for about 10 years now, and I've never experienced this 'issue' before. Twice now it has happened. The last time, they said there was an error in the curing process, redid them, and they looked just like always. This last time they are telling me there is no issue, and they are within spec.

The parts are not oily, and there is a black powdery substance on each part that wipes off. The material is grade 50 steel, which is already black, so I'm not 100% if these are even coated once you wipe the black soot looking material off.

Any thoughts?

Thanks!!

Wayne Hartwig
- Spokane, Washington, USA


May 2019

A. Hi Wayne. I suggested earlier on this page the possibility that a black oxiding shop may have switched from hot black oxide to cold black oxide because cold blackened parts are often or usually smutty, with some rub off because the process involves the application of a black selenium compound, and actual oxidation of the steel is not the only (and possibly not the main) source of the black color.

When you say your supplying shop never gave you smutty parts for 10 years but now insists that smutty parts are completely normal, I wonder about the same thing again. But I have no actual hands-on experience with these processes, so hopefully a reader who does can suggest whether you need a heart-to-heart with your applicator about what changes he's been up to, or whether Mooney is just a broken record and there are better explanations for the blackening rubbing off :-)

Regards,

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


MIL-DTL-13924E Post treatment for 301SS

July 14, 2020

Q. Is it possible to certify 301 SS to MIL-DTL-13924E using a supplementary preservative other than a WD oil? The parts are thin and have a fold over that could trap water.

Thanks!

G. Brochak
- Willoughby, Ohio USA





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