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Titration for sulfuric Acid in Anodizing Bath

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,

Sandeep Dedania
Engineer - Rajkot India
November 28, 2021

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⇩ Related postings, oldest first ⇩

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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

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A. The former is correct, 'grams per liter' mean grams per liter of total solution, NOT grams PLUS a liter. For those chemists in the crowd, remember the problems you had when first introduced to Molar vs. Molal? For the uninitiated, Molar is moles per liter, Molal is moles plus a liter. And we're not talking about groundhogs! Bill Vins microwave & cable assemblies - Mesa (what a place-a), Arizona 2000 A. Marc, To answer your question, it means 165 g contained within the volume of 1 liter, not added to 1 liter. For instance if you wanted to make a 1 liter solution of 165g/L sulfuric acid and the acid you had on hand had a specific gravity of 1.84 g/mL (the usual "concentrated" sulfuric) you would do the following: Using an appropriate container accurately marked to show 1 Liter add about half the water needed, then very slowly and carefully add the acid (89.7mL = 165g). When that cooled down then the rest of the water would be added to adjust the level to the 1 Liter mark. Paul Stransky - Putnam, Connecticut 2000

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Multiple threads merged: please forgive chronology errors and repetition  🙂

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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

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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

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Q. What % of water is in sulfuric acid when the specific gravity is 1.25?

Joan Kress
- Patchogue, New York
2001

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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

Erin Fong
- New Plymouth, New Zealand
2004

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Multiple threads merged: please forgive chronology errors and repetition  🙂

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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

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2006 A. The way I always did it was as described in the "Metal Finishing Guidebook and Directory." Briefly: Combine about 100 ml water, 5.0 ml electrolyte, and a few drops phenolphthalein indicator solution. Now, titrate with 1.0 n NaOH to a pink endpoint that persists for at least 30 seconds (important!) and record the ml. titrated. Now, repeat the above procedure, but also add 10 ml 10% potassium fluoride solution. A precipitate will form on this addition - that's AlF3. What you're doing is preventing the titration from "seeing" the acidity from the dissolved Al. Again, titrate as above, and record the ml. titrated. Al (oz/gal) = (vol in first titration - vol in second titration) x 0.24 Total Acid (oz/gal)= vol in first titration x 1.308 Free Acid (oz/gal)= vol in second titration x 1.308 Your procedure may work as well - I can see why. But I always did it as above and never had any problems. Good luck! Dave Wichern Consultant - The Bronx, New York Thank you Ken. You have been a tremendous aid! - Dan 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: To a 250 ml flask pipette a 2 ml sample and add about 100 ml DI water. Add 1g potassium fluoride ⇦ this on Amazon [affil links] and 1ml thymol blue indicator and dissolve. Titrate with 1.0N NaOH to a permanent blue endpoint, record mls NaOH used as A. g/l free sulfuric acid = 24.5 x A. Repeat the above, but do NOT add the KF; record the volume of NaOH used as B. g/l Al = (B - A) x 4.5 The purpose of the KF is that it binds up the Al which will interfere with the sulfuric acid determination. This ain't to say your way is incorrect; it's probably okay. The theory is that you are determining free and total sulfuric acid, and the difference is due to the Al. James Totter, CEF - Tallahassee, Florida 2006

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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.

Adam [surname deleted for privacy by Editor]
- Cairo Egypt
2007

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Q. Hi All,
I am finding difficulty in detecting the end point in EDTA back titration for alumina, please guide me.

THANKS,
LEENA

LEENA PANCHAL
CHEMIST - India
May 18, 2009