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topic 41155

Boric-Sulfuric acid anodizing BAC5632 Issues and Answers

A discussion started in 2005 & continuing through 2016


Q. We are having problems with our Boric-Sulfuric Anodize tank. We are getting some bad pitting and what looks like corrosion on our parts. This is the 2nd time this has happened in 3 weeks. The first time we suspected contamination of the bath, but now we have a brand new bath and it has my mind boggled. Please help me with any advice as to what our problem could be.

Tony Schmaltz
Plating Shop - Seattle, Washington USA


Q. Please send your answer for the problems of pitting in boric-sulfuric anodize process.

Kario Michael
- Lod, Israel


Q. We are having problems with our Boric-Sulfuric Anodize tank. We are getting some bad pitting and what looks like corrosion on our parts. I see same question but there was no answer.

Please, please, let me know why those pitting(or burning?) are generated and how to resolve this problem.

I.S. Hwang
Aluminum treatment - South Korea


Hello, I.S. There are several other letters on-line here about boric-sulfuric anodize, and several of them mention that the process is Boeing BAC5632. Are you following BAC5632?

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


Q. Yes, we perform Boric-Sulfuric Anodize in accordance with BAC5632 for Boeing parts.

I.S. Hwang
Aluminum treatment - South Korea


A. I.S.

It is a long shot but I would check for chloride contamination, particularly if the pitting coincides with a bath make-up or new solution(container) addition.

Willie Alexander
- Colorado Springs, Colorado

July 9, 2013 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Dear sir, we do Boric & Sulphuric acid anodizing.
After the process we get pits/ black pore-like things.
Please can you throw light on this?
Thanking you,

- Bangalore, Karnataka, India

July 11, 2013

A. We really need more information on your process parameters in order to come up with an insightful response but I have found that when I have had pitting problems they usually come from either too weak of a deox/desmut solution or too much time in the deox/desmut solution.

Tim Hamlett
Tim Hamlett, CEF
    aerospace metals distributor
Tamarac, Florida, USA

July 25, 2013

A. I think your problem is not related to anodizing. I had had same problem 4-5 month ago. I noticed source of problem was extrusion and storage conditions. Long time storage profiles's surface getting corroded. After caustic bath, these pits reveal and after anodizing you can see it. Solution: profiles not to wait too long time; avoid humidity storage; and also I wonder do you see these pits for bright profiles after anodizing? I don't see so far... because these profiles not treated with caustic.

Alaattin Tuna
- Sakarya, Turkey

Boric Sulfuric Acid Anodize tank analyses

May 10, 2016

Q. I am looking for a titration procedure with factor for boric acid and sulfuric acid. I am having difficulty getting the correct concentration for each and I've tried three different methods

Christy S
lab tech - Savannah, Georgia

simultaneous May 10, 2016

A. Christy, it would be helpful to know what 3 methods you have tried, so that your follow up reply is not I tried that and it does not work.
If this is to a Boeing spec (since they patented it) then they will have a specific way to test for it.
I will speculate that it would require a very good pH meter and possibly an autotitrator using a weaker titrant than what you are using. Boric has 3 inflection points that might be hard to find. Impossible with a rapid titration or normal 1.0N sodium hydroxide.

James Watts
- Navarre, FL

May 10, 2016

You can easily determine total acidity via a titration with 0.1 N NaOH to a phenolpthalein endpoint. I imagine that you could isolate the boric by titration to a method orange endpoint with the same solution. Plenty of stirring and slow the titrant.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

May 11, 2016

thumbs up signThank you for all your help. Yes, I am using a Boeing spec for the titration procedure. The Procedure No. I used is B-281A of which uses 1.0 N NaOH as the titrant. I have started over and redone the procedure and finally got my end results in reason from what they were. I appreciate all the advice on this and will utilize it to my advantage. Thank you!

Christy Sanchez[returning]
- Savannah, Georgia

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