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topic 44450



Q. My question regards testing alkaline soak cleaners for the ratio of free to total alkalinity. We have an alkaline soak cleaner which is titrated on a regular basis for cleaner concentration, with subsequent cleaner additions made based on the analysis results. We notice a reduction in cleaner performance over time. It has been suggested to us that measuring the free/total alkalinity ratio would give us more information as to the effectiveness of the cleaner, and allow us to decide when the cleaner should be dumped vs. further additions. I would like recommendations of a specific method to measure the ratio, as well as any insight as to interpreting test results. Thanks for your help!

Thomas Kemp
Metal Finishing employee - Erie, Pennsylvania, USA


A. I think you need to check the oil content and the sludge at the bottom of the tank. Usually 3000-3500 ppm of oil if found the cleaner than the bath should be discarded. Do regular filtration and oil skimming depending on how many hours you run your plant.

I hope this helps you.

Best Regards,

Anurag Kanaujia
- New Delhi, India


Q. I am also looking for that test. We have a skimmer on our tank but I do feel that a total alkalinity test is a very good idea, especially on our passivation system where clean parts are so very important.
Can anyone help?


Micheline Forth
metal works - Savannah, Georgia, USA

First of two simultaneous responses -- (2007)

A. This is the basic test we sometimes use;

10 mls of cleaner to 100 mls of DI water.

Add 4-5 drops of phenolthalien.

Titrate with 1N NaOH^HCl until clear. Record amount=mls#1 (this is normally the same titration as given by the supply house.)

Add 4-5 drops of Methyl Orange.

Continue titration until color change. Record amount =mLs#2.

(mLs#1 X 133)/(mLs#2)=Cleaner Activity

---a Cleaner Activity below 75 probably needs changed or bumped. When the cleaner is old you will get a good number when you titrate using phenol but with methyl orange it will "pop" you on the activity rating.

Hope this helps.

J. Ott
plating shop - Harrisburg, Pennsylvania


J Ott, take a look at your procedure. It is an alkaline bath, so you can not titrate it with NaOH. You probably meant 1N HCl.

James Watts
- Navarre, Florida


Yup, that's what I meant sorry for the typo.

J. Ott
Plating Shop - Hbg, Pennsylvania

Second of two simultaneous responses -- (2007)

A. I think total or free alkalinity will help to some extent, but for finding effectiveness of degreasing chemicals to check oil content of the cleaner bath will help more.

Milind Padwal
- Pune, India


Q. I am interested in this, I am familiar with acid titration for determining cleaner concentration, but how does one go about analysing the oil content of the cleaner?

John Reid
- Brisbane, Qld, Australia


A. The basic titration test for Alkalinity is as follows:

- 10 mls of cleaner bath solution.
- Add 4-5 drops of phenolthalien.
- Titrate with N/10 HCl until clear. The reading you get thru the burette is the total alkalinity.

To check Oil content in the Degreasing Solution following is the test:

- 50 ml of bath solution is heated with 50% H2SO4 in 100 ml measuring flask or cylinder in a water bath. The separated out oil layer volume is noted.
- % of Oil Content = Volume of Oil Layer x 2
- Oil content is permissible up to 4-5%; above this level the bath needs to be discarded. The experiment is carried out once in two weeks or depending upon the production load.


- New Delhi, India

July 22, 2010

Q. Thanks for all people that have been contribute to this topic.Actually by now, I try to find out the simple method to analyse oil content of degreaser solution. I have tried to analyse oil content by extraction solvent - water - oil. I use n-hexane. But, the result is disappointing (not valid).

Ok, by the way I just tried this method above (using H2SO4) but, after boiling, the solution became a jelly, not separated oil-water. I will very much thank you if somebody can explain to me why this is happen?

Thank you

Made Antana
chemical supplier - Jakarta, Indonesia

January 19, 2012

A. Perform the Free Alkalinity and Total Alkalinity titrations as instructed in the other posts.
The total to free ratio starts out at 1.7-2.0:1.0.
Once this is approaching double the initial ratio of 3.4-4.0:1.0, you should consider dumping the bath. If a total dump is not an option, then drain off at least 1/3 of the bath and refill, add chemical.
You can make your cleaner bath last longer and save money, if you take the overflow from the following rinse and add to the cleaner tank as it needs water.
For the acid-split, follow the instructions in the other posts, except do not heat the cleaner. It will heat up on its own (exothermic) when you add the 50 mls of acid to the 50 mls of cleaner. As the oil that floats to the top of the cylinder approaches 3 mls, consider dumping the bath.

David Yopp
Sr. Chemical Sales Consultant - Louisville, Kentucky, USA

May 30, 2013

Q. I have a little confusion in the method of measuring oil contents. Please guide whether 50% of sulfuric acid means 50 ml or 50 % its strength? The exact quantity for 50 ml degreaser bath sample?



asim altaf
- lahore, pakistan

May , 2013

A. Hi Asim. I believe it's both. The procedure requires 50 ml of 50% strength H2SO4.


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

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