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topic 15288

Need to add an aluminum bright dip step to our anodizing process

A discussion started in 2002 but continuing through 2020


Q. We have a machine shop and make aluminum parts. Right now we have a small anodizing setup and are wanting to add a bright dip step to our process. Any help on what we need and what to do would be appreciated.

Andy McClellan
- Blountville, Tennessee, US


A. While some anodizing shops obviously have bright dip provisions, most don't because it is a problematic process even for a professional anodizing shop Andy.

You need a solution of phosphoric-nitric acid operating at over 200 °F. This needs to be contained in a double walled type 316L SST tank. Then there's the ventilation: the solution evolves copious amounts of mustard colored noxious nitric oxides not only from the bright dip tank, but through the rinse tank as well; it requires a garage type exhaust system rather than lip exhaust. The NOx fumes are difficult to scrub because they are soluble. One shop that I know of has two complete wet fume scrubbers in series, and it's still a battle for them to control the NOx fumes. Rocker type agitation is required. There is also a bit of skill necessary in racking and agitating the parts so there are no spots where gases accumulate, resulting in poor brightening.

Anything can be done, and it's not my role to discourage you, but bright dipping is a much bigger program than most installations of a process tank and a couple of rinses, so I strongly urge you to see at least one bright dipping operation before going any further. Good luck.

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


A. Andy,

Be prepared to open your wallet...Ideally you'll want a 316L SS tank (double-walled, is recommended), a very corrosion resistant heater (capable of at least 175 °F), plastic ventilation (the gases are EXTREMELY noxious/corrosive), fume-scrubber, and a warm rinse tank (the solution is very viscous, and rinses better in warm water). The solution is basically a phosphoric/nitric acid mixture; usually you'll find a little bit of acetic and-or sulfuric acid thrown in there also. You can make your own bath, or there are many commercially available products out there. If you want to make your own bath, I'm sure you'll be able to find a recipe, just search the archives ... there are many questions/answers on this subject, plus some more things that I probably haven't mentioned.

Good luck, and be careful ... this is a pretty nasty process.

Marc Green
Marc Green
anodizer - Boise, Idaho


A. You might want to investigate electro-polishing instead of bright dipping. There are proprietary processes that do not contain nitric acid so they don't produce nitric oxide fumes. You need a rectifier but that's probably cheaper than a fume scrubber.

Guy Lester
- Ontario, California, USA

December 3, 2010

Q. I am in the same situation as Andy - small hobbyist looking to bright dip but have also been warned about the danger and complexity of doing so. I ultimately determined it is not worth the hassle and money.

What about sending my parts to a professional shop to be bright dipped, then anodizing and dying myself as normal? Do the parts need to be anodizing immediately after the post-Bright Dip rinse or can they sit a while? I imagine I would need to clean the parts after they are shipped back, would this basically the effects of the bright dip?

Thanks in advance.

Nate Smith
- Hamilton, OH U.S.A.

May 10, 2013

Q. Hello,
I have a customer who requires bright anodized parts for boats. Parts are already mechanical polished but when they are anodized thru a normal process they turn into a milky blue finish and brightness is noticeably reduced.
I was told that their current provider uses a brite dip process after caustic etch and prior to anodizing process. Parts from this supplier keep original brightness and looks like a yellow nickel finish while mine looks like a blue-milky chrome finish.
My inquiry is: Is brite dip (or electropolishing) required to get this bright finish even though parts are already mechanical polished or can any parameter in current anodizing process be changed in order to obtain same bright result?
Thank you

Miguel Morlan
- Tijuana, B.C. Mexico

May , 2013

A. Hi Miguel. One anodizing parameter than can be changed is the thickness of the anodizing. Anodized coatings are not full transparent but translucent. Usually, in order to preserve the brightness, quite thin anodized coatings are applied to bright dipped parts -- usually not more than .0002" thick. I would suggest that your first step be to compare the thickness of your anodizing to that of their current provider.

A second parameter is the etch. I don't think you should be etching at all. Good luck.


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

May 14, 2013

A. Hi Miguel, As per your post it's been understood that you want a finish which should appear like nickel plating or you can say it should look like stainless steel.
I am not sure whether anodizing aluminium with low micron or not etching it will solve the process.

In my opinion you should better go for Electrobrightening process or chemical bright dip process.
To begin with I would like to inform you that both the processes are nasty and require good monitoring and non - conventional exhaust system, especially in the case of chemical brightening. Nitro-oxide fumes in chemical bright dip are a real pain.

So if you have good volumes, then only you go for it. It also gives you good money compared to other conventional finishes.

Happy Anodizing

Sumit Lodha
- Ahmednagar, Maharashtra, India

Considering installing a bright dip & anodizing facility for small parts

March 17, 2020 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hello guys,

I work for a company that makes of small aluminum parts in Connecticut.
We'd like to see what it would take to get set up to do some of our own Type II Bright Dip Anodizing.
Can any of you point me in the right direction?

Thanks for your help.

Brint Mclellan
Employee - Southington, CT
  ^- Privately contact this inquirer -^

March 2020

A. Hi Brint. Before going too far down a path that you may not necessarily need to go down, I think you might want to double-check whether you actually want/need to do bright dipping. This isn't done just because you want a reasonably shiny look; rather, it is a quite specific purpose process designed for making mirrors and reflectors from particular aluminum alloys.

I mention this because Type II anodizing is a widely implemented technology and you certainly could either install a facility pretty straightforwardly, or of course farm your parts out to a good number of anodizing job shops. But, as you can read above, bright dipping involves a very hot, extremely corrosive nitric acid plus phosphoric acid mixture that rapidly evolves mustard-color fumes which are neither safely contained nor sufficiently scrubbed with conventional exhaust technology. For this reason there are safety issues and environmental issues which most metal finishers aren't faced with ... so it can be a big job to install and operate such a facility in house, and difficult to find vendors offering the service.

Your RFQ is posted so potential vendors can reach you, but you can also google or look elsewhere for "anodizing equipment". Good luck.


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

March 18, 2020

thumbs up sign Thanks for the reply Ted.
We have a couple local plating companies that perform this service for us but, but they've been falling behind lately. And honestly their quality isn't what it used to be.
We're just looking for another option is all.
Again, I appreciate your time spent commenting.

Brint Mclellan
Employee - Southington, CT [returning]
  ^- Privately contact this inquirer -^

April 7, 2020

A. If you surveyed Anodizing job shops you would find that only a small percentage actually do a Brite dip process. The reason for that is it is real nasty material/very dangerous and requires replacement of your building in 5 years(just kidding). But yes if you approach it like it doesn't matter it will eat your facility up. So I suggest you find a shop that is good at it and stay with them!

drew nosti
Drew Nosti, CEF
Anodize USA
supporting advertiser
Ladson, South Carolina

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