Letter 854

Hot vs. cold black oxide

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I work in a tool room as an apprentice and would like a comparison of durability between black oxide done with the cold method and the hot method. thank you very much.

Thomas M. Herpel

Room temperature blackening with proprietary solutions is more expensive and less durable, Thomas, and doesn't look as good. However, hot black oxiding is a nasty, dangerous, process. So, if the durability of room temperature blackening is sufficient for you, and the cost is affordable, it is certainly worthwhile.

How much less durable, I can't really say though, and whether it will prove "durable enough" would depend on the application. Best of luck!

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Tom,

Ditto on what Ted said. A well done hot process looks a lot better and my gut feeling is that it is ten times as durable as a well done cold process. The cold process is adequate for most of the tool room uses. Have done both and unless you absolutely need the better protection of hot, use the cold. Hot is going to cause you some problem with EPA more so than the cold. Personal feelings.

James Watts
- Navarre, Florida

Ed. note: Please see our FAQ on Black Oxide & Cold Blackening.

I'm very interested in the cold process for auto parts for personal use and want to find a local dealer for the chemicals. However I have the background to set up a small garage based unit for local hot rodders. any help will be appreciated.

john g.

If you do, that will make you a Hazardous waste generator. suggest that you check with your region of the state EPA and with your local sewer folks before you go any further. You probably will change your mind. Minimum fine is substantial if you are caught. If an angry customer turns you in, they will visit you to clear the complaint.

James Watts
- Navarre, Florida

James,

Which process would make me more of a hazardous waste generator, the hot method or the cold? Do you know of any documentation comparing the waste concerns of both methods?

Bob P.
- Toronto, Ontario, Canada

Response to John G. If you really have the proper background to install a mini plating shop in your garage, then you should know will be exposing children, pets and neighbors to dangerous chemicals. You should also be aware that you will have chemicals and waste water to dispose of, and that you need a city permit, a state permit and EPA clearance to do all of this.

Are you prepared to put in a separate sewerline, pay the business fees and license fees to all the proper agencies, or take the livelihood from an honest, reputable plating shop that does all these things.

Lee Garcia
- Reno, Nevada

You people make way too big a deal out of this EPA stuff. I've been plating copper and nickel, and anodizing aluminum for YEARS in a very visible, well known shop 1 block from a county wastewater treatment facility, and have NEVER EVER EVER even spoke to one single EPA or any other agency representative. I have no special sewer line, nothing. I collect any wastewater I have in HDPE 50 gal drums and have it picked up by a local environmental service company who disposes of it for a fee. Stop trying to discourage people from getting into the hobby by throwing a bunch of legal mumbo jumbo at them. Why even bother to have this forum if all your gonna do is try keep all this century old plating stuff a "secret" just so you can make more money? A small 2-5 gallon plating line can be built any where, garage or basement included.

Mike Horan
- Atlanta, Georgia

You are very welcome to your opinion, Mr. Horan and, as you see, we're very happy to publish it!

It is one thing to use chemicals as a hobby. But if you sell metal finishing services as John G proposes, you are operating a plating business, so please glance through EPA40CFR, especially the subheadings on waste water, sludge accumulation, nitrate generation, and air emissions estimating. Or go to a hazmat course offered by AESF, or Lion Technologies, or your local community college. Go to the library and read a couple of issues of Plating and Surface Finishing, Metal Finishing, or Products Finishing [link is to product info at Amazon]. Attend the annual plating industry/EPA meeting in Washington DC. Then try to explain to yourself under what grounds you think you became exempt.

You asked What good is this forum if it doesn't encourage hobbyist plating? Well, what good is a police force if they don't serve me breakfast in bed? And what good is an air conditioner if I can't barbecue a steak on it? This forum is directed towards professionals and their shop problems, as well as amateurs and their metal finishing questions -- but it is not directed at tempting people to injure themselves, violate laws or jeopardize the public safety.

 

Ted Mooney finishing.com Brick, New Jersey

Curiosity has me in it's grip today.

I do gunsmithing once in a while. So far, sending parts out hasn't been too tough, but I'd like to add to my in-shop abilities. Some things MIGHT be better if I had some control over them myself. Getting parts back plated too thick, or not masked properly...

I found, well, Ted's response a bit presumptuous, and rather inflammatory. Ya, it was a flame...but a semi-informative one. Listed a few areas for me to look into...

Being interested in the plating/finishing processes, I'd like to know more about the laws involved, and what needs to be done to actually DO some plating/finishing on my own once in a while. Truth be told, it's MY judgment call as to what will be "too expensive" to justify it. Likewise with the legal research. It's MY responsibility to ensure I conform with law, specifically those that would apply to ME: MY application, quantities, location, whether to hire a lawyer to find all of this out, etc...

Case in point: Some businesses ARE EXEMPT from OSHA. Law is not always the same, it's up to the individual to make sure they comply to whatever laws applicable. Real Estate businesses are exempt from OSHA, BTW...Supposedly not enough injuries per year to justify inspecting them...Hmph...

Anyhow, rather than blow someone off with a flame, next time do it with some finesse. Information shared responsibly, AND IN A MANNER THAT IS USEFUL, is worth a lot more than some cheap shot at the auto parts plating guy.

Enough to think about.

Take Care,
RJ

Robert Johnson
- Berthold, North Dakota

Your view of the situation, Mr. Johnson, reminds me of the way zealots react to political ads. If they want to agree with one side, then they see that side's ads as "only saying what has to be said" (no matter how vicious and misleading the ad actually is). And they see the other side as engaging in "attacks" if they challenge any of the misleading claims.

James Watts and Lee Garcia warned the initial writers that there are EPA problems involved operating a shop with this kind of chemical processing. To that, Mr. Horan responded by saying they 'make way too big a deal' of it and were 'throwing a bunch of legal mumbo jumbo' at people. He implied that our website is worthless to the extent it doesn't serve the purpose he wishes. He closed by saying that our motive for the long years we've put into this site was to keep things "secret" so we could "make more money" by discouraging people from the business. Yet you did not see those repeated, provocative, personal insults as a flame!

I gave the volume number of the code of federal regulations that people should look at, and what subheadings to look under. I gave three places where people could get training. I named the principal journals serving the industry if anyone wanted to learn more. I told people the location of the annual conference where EPA keeps metal finishers advised of the regulations. And you considered this as 'blowing him off' and as not sharing information in a 'manner that is useful'. And you characterize my response as a flame :-)

Hobbyists often react petulantly when they find that electroplating isn't as easy as they hoped. Oh well.

EPA 40CFR413 and 40CFR433 make no exception for the size of a business. However, if someone is processing parts only for personal use and they neither sell a finished part nor their processing services, so that they can honestly say they are not in business, it is probably true that the federal regulations may not apply to them. However, there are still state and local laws, and sewer regulations that are violated by that chemical processing. That, as you say, depends on the situation.

 

Ted Mooney finishing.com Brick, New Jersey

For your info -
I run a small 3 man engineering shop and use a propietary supplier to supply me with cold blackening chemicals.
For a shop as small as mine, the process is probably a little expensive, but the benefit is being in control of your product from start to finish controlling your own lead time on job completion etc.
In my experience it is correct to say, though, that hot black oxide processes are much better quality.
As my company expands I am now looking into the hot process.
What process is used for cleaning the part before hot blackening?
When I cold blacken I first have to sandblast the part if it has any mill scale left, unless it has been machined, then it can go directly through the cleaning agents provided by the supplier.
what is the process with hot blackening?

Ben Pearson
- Goulburn, NSW, Australia

Those steps are the same, Ben. Scale must be removed, then the parts thoroughly alkaline cleaned before putting them in the hot black oxide tank. Usually there will be a post-dip involving a wax or oil.

The biggest difference is that hot black oxide is quite dangerous, and operators have been killed. The cause of the problem is that the process operates at about 290 deg. F so there are evaporation losses, and water must be constantly added. But water flashes to steam at 212 deg F. If a slug of make-up water finds itself surrounded by this 290 deg solution, it can virtually explode into steam, propelling gallons of this hot concentrated caustic onto an operator. Some people have been killed and many severely burned, so extreme care must be used to prevent it from happening, and protective gear worn in case it happens anyway. Good luck.

Ted Mooney finishing.com Brick, New Jersey

I'm working for someone who is interested in possibly starting a hot black oxide business and I noticed that someone said that a permit was required for plating, but I wasn't sure if that applied for a black oxide finishing company. From what I've read, finishing and plating are different so I was wondering if the law requirements were the same.

Kirsten Haney
- Acton CA United States

May , 2008 Hi, Kirsten. I do not see black oxide mentioned in EPA 40 CFR 433 (see www.access.gpo.gov/nara/cfr/waisidx_98/40cfr433_98.html), so I would say that an EPA permit may not be required. But you should check with a local field office of the EPA, or with your POTW. Good luck. Regards, Ted Mooney finishing.com Brick, New Jersey October 22, 2008 I have 35 years experience in Electroplating and spray painting in Defence organ., I like to answer any question on the above subject. Presently I am working as Manager in electronics company in Bangalore, Karnataka, India. chandramanipg - Bangalore,Karnataka, India ---- Ed, note: We have thousands of public questions on electroplating and spray painting where your input would be highly appreciated, Chandramanipg. Just find any that interest you at finishing.com/Letters and jump right in. Thanks!