Letter 30736

Brite Dip Chemical Composition / Effective Polishing Techniques  

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In regards to Type II Anodizing, I have read about a process called Brite Dipping in which the part(s) are brought to a high shine utilizing a solution of this so called Brite Dip. I have done much looking on this subject and have been unable to determine what the chemical composition of this Brite Dip solution is. Is it possibly/advisable to mix my own Brite Dip solution? Secondly, at what temperature does this Brite Dip solution operate at?

I am also looking for an effective mechanical way to polish several parts at once on a processing line environment. Currently I am buffing my parts manually utilizing a variety of polishes. What would you suggest a person use in order to increase production without losing any of the quality. Would a simple bead blast followed by a Brite Dip be sufficient?

Thanks so much for your time. Cheers!!

Daniel DeGueldre      anodizing shop entrepreneur Ste. Anne, Manitoba, Canada

I am quite surprised that nobody has offered any input to this post over the past 1-1/2 weeks. Perhaps this Bright Dip solution is an old family recipe and not meant for prying eyes. Perhaps there are several recipes utilized in order to mix an aluminum Bright Dip solution. None-the-less, I have found my self stumped.

I think I have narrowed down the most important chemicals required in order to mix a Bright Dip. So far I have, Phosphoric Acid (H₃O₄P) and Nitric Acid (HNO₃). I have done a lot of reading of the past weeks in regards to this question, yet I'm still stumped. I think I have the two major chemicals correct, however, the actual solution formula still proves impossible to nail down.

If you know what your Bright Dip solution is composed of or if you are mixing your own Bright Dip solution in your shop, please post your recipe here. I am also curious as to what temperature your Bright Dip operates at. Thanks so much in advance.

Cheers!

Daniel DeGueldre
     anodizing shop entrepreneur
Ste. Anne, Manitoba, Canada

It operates at about 210 degrees F. I don't know the concentrations of the two acids offhand, but they're high.

People probably don't say much about brite dipping chemistry for a number of reasons, Daniel. First, there are some proprietary suppliers, and people may not be sure if a composition they know is common knowledge or proprietary; secondly, very few anodizers do brite dipping, and those who do would naturally prefer not to put others in competition with themselves, so they are very unlikely to print the formula their shop successfully uses on the internet. Third, those who are familiar with it realize it is a nasty solution that requires specially designed fume containment not conventional lip exhaust or push-pull, and special fume scrubbers to deal with the wild NOx fuming, and well engineered secondary containment because it is aggressive even to relatively expensive construction materials like 316L stainless.

Speaking for myself, I cheerfully give anyone a few minutes of my time, but when we get to aluminum brite dipping, it's so full of "You didn't tell me THAT!" issues that it's a topic that can't be quickly dispatched. I can't offer a half day of uncompensated consulting engineering, and tend to not want to be pulled into a discussion when I see such a long road in front of me :-)

This is a good area to start with a proprietary solution from a vendor who will give you some help. I believe Albright & Wilson may be one; search for their Phosbrite.

Signing off . . .

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

Well...For those who care to contribute or simply for those who wish to experiment, I have learned of the following formula for a Bright Dip bath :

94% Phosphoric Acid & 6% Nitric Acid operated at a temperature of 180-185F.

If this seems crazy, please correct me. I'm simply relaying information which has come across my desk.

It should be noted that this solution requires extreme caution when handling. Use in a properly ventilated area and dispose of the waste accordingly!!

Daniel DeGueldre
     anodizing shop entrepreneur
Ste. Anne, Manitoba, Canada

Typical home-made solution is as follows:
Phosphoric Acid 73-83% (vol)
Nitric Acid 2-5% (vol)
DI Water 14-23% (vol)

Heated to a temp of 200-210 F.

Like Ted said.. extremely nasty stuff, and use with caution. This bath works well on wrought alloys, not castings (or alloys with high silicon content). Nitric acid content must be kept stable, or you'll have undesirable results. Also heed his advice on finding a supplier of pre-made brite dips. They are much easier to work with, but if your intent on making your own, the above recipe works well. Use double walled 316L tanks to contain your solution (I would even coat the inside with a fluoropolymer coating).

Marc Green anodizer - Boise, ID, USA

Bright dip for aluminum:
phosphoric acid(d=1,75) 65%
nitric acid(d=1,5) 25%
acetic acid 10%
30-60 sec, 80-110 C temp.

Goran Budija
- Zagreb, Croatia

DEAR: SIR I HAVE A RADIATOR SHOP AND USED BRIGHT DIP FOR 48 YEARS ,AND YOU DONT NEED ANY HEAT USE COLD , I USED A PLASTIC BOTTLE LAY ON IT TAKE NIFE CUT 10 INH HOLE IN IT PUT THE BRIGHT DIP IN ABOUT 2INH AND PUT THE PART IN SIDE ,LOOK AT IN 20 MIN IF CEAN WASH IT WITH WATER , IF IT REAL BAD YOU LEAVE IT IN LONGER OK . BRIGHT DIP IS A ACIDS DONT LEAVE THE PART HAFH WAY OUT OF THE BRIGHT DIP ,IT WILL CUT THE PART OK HOPE THIS HELP YOU DOUG BROWN

DOUGLAS BROWN
- MAXWELL, TEXAS

I know of 2 basic formulas for bright dipping aluminum.
The typical R5 process consists of 80% phosphoric acid, water, and HNO3. specific gravity should be around 1.65
You need 1000 ppm of copper (as cooper sulphate) and dyammonium phosphate or urea (2%) as a fume supressant.
The nitric acid concentarion is the 3 to 4%, water should be about 10%, the balance is the phosphoric acid. Make sure you use 80% phospphoric acid.

The second formula, similar to the phosbrite 174, is a mixture of phosphoric acid and sulphuric acid. the specific gravity should be about 1.70. Also use cooper and the fume supresant. Same concentrations as before : Nitric 2 to 4 %, about 10% water, 15 to 20% suplphuric, the balance is 80% phosphoric acid.

Operating temperature should be over 212 degrees, as the b/d generates water. with the heat you control the specific gravity of the solution. (also by adding water when necessary)
The immersion time should be from 1 to 3 minutes (depending on the alloy).

To formulate a B/D bath is pretty simple - a provided you with the "secret" ingredients. The real deal is to know how to operate it in a production line.

The operating parameters are very tight, if you don't keep accurate controls, you are bound for disaster.

Martiroz Avoyan
- No. Hollywood, California