Soak Cleaner / Degreaser: Alkalinity test & oil content

A. Hi, Mohd Tariq.
The pH of your alkaline cleaner is certainly not 2-3 :-)

But we appended your question to a thread which explains how to titrate the concentration (and, as importantly or more so, how to analyze the oil content). If anything is unclear, please come back with specific questions.

Luck & Regards,

A. Dear Sir:

The best way is to extract the oil with some solvent like Methylene Chloride. Then dry the solvent and weigh the oil residue.

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 then 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,

A. This is the basic test we sometimes use;

10 mls of cleaner to 100 mls of DI water.

Add 4-5 drops of phenolphthalein ⇦ this on eBay & Amazon [affil links] .

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 ⇦ this on eBay or Amazon [affil links] .

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 ⇦ this on eBay or Amazon [affil links] it will "pop" you on the activity rating.

Hope this helps.

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.

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

- 10 mls of cleaner bath solution.
- Add 4-5 drops of phenolphthalein ⇦ this on eBay & Amazon [affil links] .
- 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 [100 mL flasks on eBay or Amazon [affil links] 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.

Regards

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.

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

Regards,

A. Hi Anis. We added your question to a thread where the test method is explained. Anurag suggests that at about 4-5% oil content the solution should be discarded, and David has suggested about 3%.

If anything remains unclear after reviewing this page, please re-post in terms of what you don't understand. Thanks.

Regards,

A. Hi Geoff,

I can't think of a specific test to determine whether a solution is "spent". I guess you do a waterbreak test after the alkaline cleaning/degreasing operation. I would suggest that, after you have "reconditioned" your solution, if you cannot get a consistent pass for the waterbreak test, the solution is now "spent".

A. Hi Chris,

First problem you have is that alkaline cleaner/degreasers are designed to emulsify the oil, so they do not simply sit on the top of the tank, otherwise you'd be re-contaminating your parts as they leave the tank.

If you are using NPB prior to alkaline cleaning, I can't imagine there is very much oil left on the parts at all, assuming the degreaser is set up correctly.

A suggestion, with no promise that it will work...

Take a sample of the process bath at the surface and place in a clear beaker/container. Leave it sit undisturbed for 24 hours and look to see if you have any oil separation. If there is free oil it will sit on top of the bulk fluid as a separate layer.

Best of luck.

A. We use a very simple test to determine if the layer on a surface is oil or surfactant.
Take some of the layer in a flask, add some water and mix it well.
Surfactant will be soluble in water, oil not.

Thank you Daisy. That makes a lot of sense and is a very simple test to perform.

A. Hi, Chris,
1. The purpose of aqueous degreaser is to remove the oil from the part surface. If your parts are "water break free" after cleaner/degreaser, your solution works well.
2. Generally speaking, there are two groups of aqueous cleaners/degreasers - emulsion cleaners and alkaline cleaners. Emulsion cleaners convert the oil to emulsion and you will not see the oil film on the surface of the solution until it become saturated and should be replaced. No skimmers used in these solutions because no oil film is expected. These solutions are mild to slight alkaline and could be used to clean aluminium parts.
Alkaline cleaners are much more alkaline and will dissolve aluminium. They are formulated to "strip" the oil from the part surface and not to emulsify it. In these solutions you will see the oil film on the surface and use of skimmers is necessary.
3. The following method can be used to determine the oil content in the emulsion cleaner:
a) Fill the Cassia flask to the 100 ml mark with the cleaner bath to be tested.
b) Add 2 g of sodium chloride and swirl to dissolve.
c) Slowly and carefully (while swirling) add the concentrated hydrochloric acid to the 110 ml mark. Allow to stand for about 5 minutes.
d) Mix by inverting 3 times. Vent after each up-ending. Always point the flask away from the face.
e) Allow the mixture to stand undisturbed for 2-3 hours and read percent of oil.
Explanation: The purpose of sodium chloride and HCl addition is to break the emulsion and to free the oil.
We used this method many years ago, but finally decided that control by "water break test" is much better and practical.

Good luck!
Alex

A. It is quite possible that you are trying to solve the wrong problem.
What looks like oil floating on an alkaline cleaner is frequently caused by excess detergent separating out. This is known as "Salting Out".
The root cause is often over-enthusiastic addition of cleaning salts on the premise that more is better and will improve cleaning. It doesn't.
Easy to test. Shake a sample of "oil" with a large excess of plain water. If it dissolves, it is not oil.
The treatment is simple. Dilute the cleaner to the manufacturer's recommended concentration and reduce the additions. You will save money and probably have no need for a scimmer which is just throwing away expensive detergent.

Thank you Alex and Geoff for your most valuable input.

The product we are using is called Enprep 576E. It is a MacDermid/Enthone product.

The TDS states that is is a non-cyanide, phosphate free cleaner that is effective in removing rust, oils, silicated drawing compounds and lubricants. It uses a blend of deflocculants in addition to alkalies and detergents.

I think what we are seeing, AND CAPTURING, with our oil skimmers is not 100% oil. I feel that part of the cleaner chemistry is being captured by the skimmers.

The product is dark brown in color which makes it very difficult to tell what is floating on the surface.

Our lab technician performs a titration on the cleaner baths once a week. Additions are based on titration results. We keep the concentration in the middle of the TDS recommended range, so hopefully there is no cleaner addition overload.

Quality technical support is very difficult to get from the chemical suppliers and manufacturers these days.