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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
-----
Titration for sulfuric Acid in Anodizing Bath
Tip: Readers want to learn from your situation,
often just skipping abstract questions.
Q. Dear sir,
Many thanks for easiest method of sulfuric acid titration for anodizing. So please give regular updates regarding this type of method.
Best regards,
Engineer - Rajkot India
November 28, 2021
A. Hi Sandeep
I've posted the exact titration and calculations here before, and can't recall them away from my desk, but look around the site history and you will surely find them [Ed note: here's that link]. The biggest issue is knowing how to separate straight acid-base without the dissolved aluminum (And other hydroxide forming compounds) interference. You will always need to do 2 titrations to tease them out. If you get this message before you figure it out, reply and I will send better instructions when I'm at my lab.
Cheers.
Lab Rat and some other things - Greenfield
December 24, 2021
⇩ Related postings, oldest first ⇩
Q. When one is sulfuric acid anodizing, say, at the concentration of 165 gr/liter, does that mean for every liter if solution, there is 165 grams of sulfuric acid? Or does that mean that the 165 grams of acid is added to one liter of water? I'm a little confused over this issue.
Thank you,
Marc Green
anodizer - Boise, Idaho
2000
A. The former is correct, 'grams per liter' mean grams per liter of total solution, NOT grams PLUS a liter. Bill Vins microwave & cable assemblies - Mesa (what a place-a), Arizona 2000 A. Marc, - Putnam, Connecticut 2000 |
Multiple threads merged: please forgive chronology errors :-)
Q. I've really enjoyed the feedback from this site, I've found all of your answers very informative. Now I have another titration question. Do you guys have an opinion as to which Sulfuric acid titration is the best (for a standard anodizing tank)? I think I've tried 3-4 of them, and had varying (slight) results. I prefer using a potential titration, as I've found that the colormetric titrations vary, as each individuals perception of colors is different.
I was also wondering if any of you had used a piece of equipment that is supposed to be able to calculate the exact square footage of work being place in the anodizing tank, and adjusts the amperage accordingly. As we are a job shop, we run numerous shapes and sizes of parts at the same time, and calculating the surface area can be cumbersome, and inaccurate...so we just end up anodizing by voltage, which I know isn't the correct way to do things. We do spend the time to calculate surface area for our hard anodizing..but the decorative work has always been a pain to figure out.
Once again, thank you for all your input.
Marc Green
anodizer - Boise, Idaho
2000
A. A titration with a very good probe and meter will be the easiest to replicate. If you are testing for aluminum, then you are adding fluoride in an excess, which is hard on a conventional glass bulb probe and very hard on an analytical one. There are high quality probes made that will stand up to short term fluoride. Most are solid. They are not as cheap as low end probes, and are about on a par with high quality ones.
Titration with indicators is not all that bad if all of the operators are trained by the same person and not allowed to do the test until certified by the trainer. Consider taking a picture of the endpoint with a macro (close up) lens, having several prints made and issuing one to each person with a couple in reserve.I have never heard of a practicable and affordable way to estimate area. By keeping a log of the calculated area by part number, you should have about 90% of your parts as a known.
- Navarre, Florida
2000
Q. Thanks for replying, James..I am testing for aluminum content, as well as sulfuric concentration..but am not using fluoride..I'm just using 1.0N NaOH [1N NaOH on
Amazon [affil links]
to a pH of 3.6 (for sulfuric concentration) and then carrying the titration to a pH of 8.5 for the Al content
(subtracting, and multiplying by 1.8)
I do use methyl orange
⇦this on
eBay or
Amazon [affil links]
, and phenolphthalein
⇦this on
eBay &
Amazon [affil links]
for indicators, just to know when I'm getting close to my desired endpoints. I believe we are using a quality meter, its an Accumet..and it was a spendy sucker, so I'm assuming its a good one, its quite consistent. I am curious about using fluoride, if you had a minute to detail that method for me, I'd appreciate it.
Thanks,
Marc Green
anodizer - Boise, Idaho
2000
A. The way I always did this analysis was to titrate a 2.00 ml portion of sample to a phenolphthalein endpoint, both alone, and with a 5 ml portion of 10% potassium fluoride
⇦this on
Amazon [affil links]
added. A blank titration also needs to be run on a mixture containing just the potassium fluoride. This volume is subtracted from the volume used in the second titration above. Values for total acid, "free" sulfuric acid, and aluminum can then be calculated. It's important to be consistent in the rate of addition of the titrant, and endpoint recognition. My rule of thumb was always to titrate slowly to a pink endpoint that persists for at least 30 seconds.
I have also done a titration for just aluminum using a more elaborate procedure when a more accurate result was needed. An excess of EDTA standard solution is added to a diluted portion of sample, the pH lowered to less than 2 with HCl, and the mixture boiled for 5 minutes. Then, ammonia
⇦this on
eBay or
Amazon [affil links] is added to a pH of about 9, PAN indicator added, and the excess EDTA titrated away with a standard copper solution. This procedure is tricky but can yield very good results with a little practice.
Dave Wichern
Consultant - The Bronx, New York
2000
Q. What % of water is in sulfuric acid when the specific gravity is 1.25?
Joan Kress- Patchogue, New York
2001
A. Hi Joan. It's 1/3 acid 2/3 water, but you can easily Google "specific gravity vs. sulfuric acid concentration" and have the answer for every specific gravity rather than just this one.
But because you have posted on a thread about sulfuric acid in anodizing solutions, and in case you are referring to an anodizing bath, it's important to warn you that dissolved aluminum will render this approach meaningless after initial make-up.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
November 2021
Q. Hi there
I am student and am also attempting to do a similar analysis on the amount of aluminum and sulfuric acid in water from an anodising bath.
Could you please tell me what the Potassium Fluoride does in this titration, and how these calculations are actually done?
Cheers
- New Plymouth, New Zealand
2004
Multiple threads merged: please forgive chronology errors :-)
2006
Q. Hello finishing.com world. As you may already know, I've been working on my small Type II anodizing business for nearly two years now. I'm finally anodizing like crazy and having a ball doing it! We're mostly doing custom work (multi-color stuff) and things are going well and this is mostly in part to you folks who have aided me so much throughout this entire journey. It is you people I thank!
As my business has been completely funded out of my own personal bank account (with some help from my brother's custom machine shop), I still haven't been able to get together the funds to purchase the textbooks I've been so desperately wanting (The Surface Treatment and Finishing of Aluminum and Its Alloys). As a result, most of my questions have been answered here at finishing.com or other smaller "do-it-yourself" forums. Today is no different from any other day I drop by...I have a question.
I am having a difficult time finding the procedure for titrating my electrolyte tank. Obviously I want/need to be able to check the acid and aluminum levels. I may have come across something and have been playing with it with some decent results. Below is my method of titration, apparatus and calculations utilized. Does this look anything like the right method to all you pros? Any and all help is greatly appreciated!
Apparatus & Reagents Required
0-50 ml buret
400 ml beaker [beakers on
eBay
or
Amazon [affil links]
250 ml graduated cylinder
pH Meter
NaOH 1.0N [1N NaOH on
Amazon [affil links]
(sodium hydroxide)
Procedure
1. Fill buret with NaOH 1.0N (sodium hydroxide)
2. Measure 200 ml of DI water with graduated cylinder and pour measured amount into 400ml beaker.
3. Pipette
[pipettes on
eBay or
Amazon [affil links]
5 ml of electrolyte solution into beaker.
4. Insert pH meter into beaker.
5. Slowly add NaOH from buret into beaker until a pH reading of 3.6 is reached. (Constant stirring required)
6. Record reading on buret as Value A.
7. Slowly add NaOH from buret into beaker until a pH reading of 8.5 is reached. (Constant stirring required)
8. Record reading on buret as Value B.
Calculations
g/l H2SO4 (sulfuric acid) = Value A x 9.8
g/l Aluminum = (Value B - Value A) x 1.8
Or allow me to rephrase the question :
What is required, what is the process and what are the calculations for titrating the electrolyte in a type II anodizing line?
Thanks!
- Dan
Daniel DeGueldre
anodizing shop entrepreneur - Ste. Anne, Manitoba, Canada
A. Hi Daniel,
The free sulfuric acid determination is correct.
Endpoint 'B' is usually at pH 10.0 (pH 8.5 corresponds to a phenolphthalein
⇦this on
eBay &
Amazon [affil links]
endpoint; the difference in mls is very small).
Aluminum content is [Al] = (B - A) x 1.35, g/L
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2006 A. The way I always did it was as described in the "Metal Finishing Guidebook and Directory." Briefly: Dave Wichern Consultant - The Bronx, New York Thank you Ken. You have been a tremendous aid! Daniel DeGueldre anodizing shop entrepreneur - Ste. Anne, Manitoba, Canada 2006 A. I had to dig out one of my reference books for this, Volumetric Analysis of Metal Finishing Solutions
[on Amazon affil links], by Andrew McFadyen (Finishing Publications, Ltd., Stevenage, UK, 1998). McFadyen gives the following: James Totter, CEF - Tallahassee, Florida 2006 |
Thank you for the help all. Very much appreciated!
- Dan
Daniel DeGueldre
anodizing shop entrepreneur - Ste. Anne, Manitoba, Canada
2006
Q. Hi everyone
Thanks for this wonderful site
I want to determine the Al2O3 and SiO2 percentage in a mineral containing SiO2, Fe2O3, Al2O3.K2O, Na2O
I have no apparatus in my lab and I need volumetric analysis not gravimetric.
Please if you can support me with calculation I will be thankful.
- Cairo Egypt
2007
Hi Adam. Anyone is welcome to answer you, but this site focuses on metal finishing not mineralogy, and you posted on a thread about analysis for sulfuric acid in anodizing so, apologies, but it's unlikely that qualified people will see your question :-(
Luck & Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hi All,
I am finding difficulty in detecting the end point in EDTA back titration for alumina, please guide me.
THANKS,
LEENA
CHEMIST - India
May 18, 2009
A. Hi Leena. Well, Dave did warn you above that it's tricky and requires practice :-)
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
November 2021
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